LIFE ZONE ECOLOGY
OF
THE BHUTAN HIMALAYA
Edited by
M. OHSAWA
Laboratory of Ecology, Chiba University
1987
Scanned from original by ISRIC - World Soil Information, as ICSU
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PART HI
CLIMATE
I
I
I
I
I
I
I
I
1
[
of the Bhutan Himalaya.1987.
Chiba University.
SYNOPTIC ANALYSIS OF TEMPERATURE, PRECIPITATION AND
MOISTURE CONDITIONS IN THE BHUTAN HIMALAYAS
T. EGUCHI
Department of Geography, Faculty of Science
University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan
ABSTRACT
Bhutan is located in monsoon Asia and is one of the important areas for clarifying the Indian summer monsoon.
However, with regard to climate, Bhutan is the most unknown
region in monsoon Asia. Therefore, the purpose of this paper is
to explain the climatic situation of Bhutan on a synoptic scale.
In Bhutan,
the moisture condition indicates a great
regional diversity. Along the southern foothills, the annual
precipitation is above 4000mm and this region is classified as
Perhumid (A type) on the basis of Thornthwaite's climatic
classification. On the other hand, in the lower Midland, the annual precipitation is around 600mm and according to
Thornthwaite's climatic type this region is classified as Dry
Subhumid(C2 type). This abrupt regional change of climate from
the southern foothills to the middle reaches is expected to occur around the main ridges of the southern High Himalaya.
The seasonal change of precipitation is more obvious in
the southern foothills than in the lower Midland.
In the
southern foothills, monthly precipitation is above 100mm from
April to October and the dry period is shorter than in the
western and central parts of the Himalayas.
The annual mean temperature lapse rate around Bhutan is
0.54C/100m and the monthly mean indicates obvious seasonal
change.
-209-
INTRODUCTION
Bhutan is located in the eastern part of the Himalayas bordering
with Assam and Tibet. On a global scale, the climates of East Asia, India and Indochina have been clarified with an increasing number of data.
However in the contact region of the three regions the climate is not
clarified from the regions which surround it. For example, the onset of
the rainy season is roughly clarified both in India and in East Asia, but
the relationship between them is obviously shown. Because there are
mountains in the areas between the two regions and it is difficult to obtain the observed data. Considering the onset of the Indian summer monsoon, it is pointed out that the region around Assam plays an important
role regarding heat sources. To clarify the climate of bordering areas including Bhutan it is important to clarify the climate in South, Southeast
and East Asia.
Bhutan is also important in clarifying the climate of the Himalayas
and the mountain climatology. However, the climate of Bhutan has not
been clarified. Papers concerning the climate of Bhutan are few. Karan
(1968) reported the climate of Bhutan briefly and classified Bhutan into
three climatic regions. However, he used the climatic data of a few stations and the
climatic conditions were mainly concluded by vegetation
type. A systematic analysis of Bhutan's climate has not been done before.
Therefore, in this paper, the author intends to clarify the climate of
Bhutan, including India and China.
REGIONAL AND SEASONAL CHARACTERISTICS OF PRECIPITATION
1. Data
In this paper only 18 meteorological stations in Bhutan are used
and ,in particular, there is no station in either the eastern part of the
southern foothills or in the northern High Himalaya(Fig. 1). Moreover, in
the other areas, the stations are almost all located in valleys. Though
the meteorological stations are not uniformly distributed, the data used in
this
paper are at least more than those used by Karan(1968) and it is
possible to analyze the climate of Bhutan in more detail than Karan did.
-210-
8 9*0'
9 2"O'
91*30
8 9"30'
BHUTAN
v
CHINA /
.
o
%
t-28'O'
INDIA
+
y
A
Ui
y
B'ÀNG'LA ^ /
vx
DESH'i ,i
r- A - S ^ V ' BURMA
\
•
(
•'»
Krn
1 +
0
1,0
20
30
40
i
i
i
50,.K
i
1- 27*30 -
+
T S A M C H I - ^ i . PHUNTSOLING
\ ƒ SARBHANG
Figure
1
x,
j
Distribution of meteorological stations in Bhutan.
/
_!_/-
27" 0 -
Therefore, the author intends to clarify the distribution and seasonal
march of precipitation in more detail than Karan did on the basis of observed precipitation data which are mean annual and monthly data for
the six years from 1975 to 1980.
2. Distribution of precipitation
In Bhutan, the annual precipitation indicates a great regional
variety(Fig.2).
In the southern foothills(ex.
Phuntsoling),
the annual
precipitation is above 4000mm. On the other hand, in the valleys of the
lower Midland(ex. Thimphu), it is around 600mm. Precipitation decreases
abruptly from south to north and its distribution is extremely complex.
This regional
difference in the distribution of precipitation is expected
to be largely affected by topographic effects. On the basis of precipitation data and topographic conditions, at least four climatic regions can
be recognized; the southern foothills, the southern High Himalaya, the
lower Midland between the southern High Himalaya and the northern High
Himalaya, and the northern High Himalaya(Fig. 2). The southern foothills
include the Bhutan Sub-Himalaya and parts of the Lower Bhutan
Himalaya. The southern High Himalaya include the southern part of the
Bhutan High Himalaya and parts of the Lower Bhutan Himalaya. The
Black Mountains are the main part of the southern High Himalaya. The
lower Midland indicates the region around the cities of the middle
reaches of each river. More detailed descriptions of topography in Bhutan
are shown by Eguchi( 1987a). In the same climatic regions, however,
precipitation differs between valleys, slopes and ridges.
Karan(1968) has already pointed out the complexity of Bhutan's
climate and tries to resolve this intricacy by the broad classification of
climate with limits determined by altitude. He classified Bhutan into
three climatic regions; the hot and humid subtropical area of Duar and
the foothills, the cooler (microthermal) region of the inner Himalaya, and
the tundra region of the Great Himalaya. The southern foothills and the
northern High Himalaya in this paper correspond to the southern
foothills and the Great Himalaya of Karan's classification, respectively.
However, Karan's Inner Himalaya are separated into two regions; the
southern High Himalaya and the lower Midland.
In the southern foothills, the mean annual precipitation is between
-212-
89
78'-
-28'
J,°KM
27'-
92'
Figure
2
Mean annual precipitation in Bhutan(6 year mean: 1975-1980).
70
Figure
80
3
90
100
110
Mean annual precipitation around Bhutan(6 year mean: 1975-1980).
-213-
4000 and 5000mm. It is the highest in Bhutan and is about twice that of
Assam in Fig. 3 (ex. Gauhati,1705mm;Dhubri,2169mm).
In the southern part of the southern High Himalaya, south of
main ridges of the southern High Himalaya, regional variety is expected
to be large. Meteorological stations are mostly located in valleys or
lower parts of slopes and consequently the precipitation data in the upper
parts of slopes or ridges are insufficient. On the basis of data at
Dhablakha,
which is the only data for the upper parts of southern
slopes, precipitation is above 3000mm. On the other hand, in valleys or
lower parts of slopes, precipitation is between 1000mm and 1500mm. On
the basis of the data for the southern part of the southern High
Himalaya, precipitation is expected to be greatest in the upper parts of
southern slopes and least in the bottoms of valleys. The upper limit of
precipitation in this area
is expected to be 3000mm or more, but less
than that of the southern foothills. On account of the complexity of
topography, precipitation in this area is expected to vary greatly between
1000 and 3000mm mainly caused by the direction of slopes or altitude.
In the northern part of the southern High Himalaya, north of the
main ridges of the southern High Himalaya, though the data are insufficient, precipitation is expected to be less than that of the southern part
of the southern High Himalaya. Decrease in precipitation from south to
north varies with the direction of main ridges and the altitude of
ridges. In the eastern part of the southern High Himalaya, the altitude of
ridges is the highest and the decrease of precipitation by topographic effects is expected to be remarkable.
Precipitation in the lower Midland varies from west to east. In the
western part, the annual precipitation is around 600mm. On the other
hand, in the central part, it is more than that of the western part. At
Tongsa, it is 1280mm and almost twice more than that of Thimphu. One
of the reasons why precipitation in the central part is more than that
of the western part is considered to be the relationship between the
monsoon flow in the lower troposphere and the topography. During the
summer monsoon season, the southeasterly dominates in the lower troposphere. In the western part, west of the Mangde Chhu(River), the ridges
extend from west to east as well as from south to north and the altitude of their peaks is more than 5000m. The southeast monsoon flow is
disturbed by the southern High Himalaya and the moisture from Assam
-214-
cannot reach fully over the lower Midland. On the other hand, in the
central part, the main ridges extend from south to north or northwest to
southeast and their altitudes are lower than that of the western part.
Therefore, the southeast monsoon flow penetrates into the lower Midland
and brings more rainfall than in the other parts of the lower Midland.
In particular, at Tongsa which is located in the southern slope of the
Mangde Chhu, the valley of the Mangde Chhu, southeastward of Tongsa,
runs straight from northwest to southeast and, therefore, the southeasterly
flow is not disturbed unlike the other parts of the lower Midland and
precipitation at Tongsa is much more than that of the other parts of the
lower Midland.
In the eastern part of the lower Midland, there are two stations,
Mongar and Tashigang. These two stations are located in the south compared with the other stations in the lower Midland, and their altitudes
are lower than the others. The annual precipitation at Mongar is only
518mm. Although the topographic conditions in this area are not known in
detail, the ridges extend from west to east south of these stations. The
precipitation at the two stations are also expected to be affected by
topographic effects and the moisture of the summer monsoon cannot be
fully accepted. In particular, the precipitation at Mongar is the least in
Bhutan. One of the reasons is considered to be that Mongar is located on
a northern slope. Therefore, the precipitation data at Mongar may not
represent the surrounding area and it may be less than the aerial
average around Mongar.
In the northern High Himalaya(the Great Himalaya),
limit is around 4000m, no meteorological data are available.
whose lower
In general, precipitation along the Himalayas increases from west to
east(Fig. 2). In Bhutan, because of the lack of data in the eastern part
of the southern foothills, it is difficult to compare precipitation longitudinally along the southern foothills. In the middle reaches, precipitation is greater in the central part than in the western part, and at
Tashigang it is greater than in the western part. On the basis of the
data at Tashigang, increase in precipitation from west to east is recognized also in Bhutan. However, the precipitation at Mongar is the least
of all the station and the amount of increase is not so great. The
precipitation data in the lower Midland is affected by topographic effects
and they do not necessarily indicate that precipitation increases from
-215-
west to east in Bhutan. This problem is very important, however, it is
difficult to resolve on the basis of the data used here.
3. Seasonal change of precipitation
Bhutan is located in the monsoon region. During November through
February the monthly precipitation is nearly zero at almost all stations
and dry conditions dominate(Fig. 4, Fig. 5, Data 1, Data 2). Monthly
precipitation increases from March and reaches its maximum in July or
August. Along the southern foothills, the increase of monthly precipitation
starts in April. From April to May and from May to June, precipitation
increases considerably and the period from June to August is the main
rainy season. On the other hand, mainly in the lower Midland, the
precipitation increases gradually compared with that of the southern
foothills at almost all stations.
Although the patterns of precipitation increase differ by area in
Bhutan, the summer concentration of precipitation, the percentage of
three months total to annual precipitation, is above 60% at almost all
stations and that of the five months from May to September is above
80%. In particular, the percentage for July to annual precipitation is
above 25% in central parts of the southern foothills and the southern
High Himalaya. Precipitation largely decreases from September to
November in Bhutan. The seasonal change from monsoon to post-monsoon
in 1985 occurred on October 19 in Bhutan(Eguchi, 1987b).
In accordance with the compiled map of average onset dates
of
the rainy season by Ramage(1971), the onset of summer monsoon in
Bhutan occurs in June. However, the increase of precipitation in Bhutan
occurs before June as well as in Assam. Though there are some problems
that the onset of monsoon is defined by precipitation, it is evident that
the onset of the rainy season is at least earlier than that of areas west
of Bhutan. The relationship between the onset of the summer monsoon
around Assam including Bhutan, that of the Burma summer monsoon and
that of the Indian summer monsoon is an important problem and
, therefore, further study is necessary.
Maximum monthly precipitation indicates regional diversity. In the
southern foothills and the southern High Himalaya, it mainly occurs in
July, but in the lower Midland it mainly occurs in August. The total
-216-
89'
27"1
Figure
4
Distribution of mean monthly precipitation in Bhutan
(6 year mean: 1975-1980).
U n i t : mm
-217-
(mm)
1000-
PHUNTSOLING
_
DHABHULAKHA.
800-
-800
600-
-600
400-
-400
200-
-200
2 3 U 5 6 7 B 9 10 11 12
1 2 3 U 5 6
7 8 9 10 11 12
Month
CHUKHA
300-
THIMPHU
200-
-200
100-
-100
1
2 3/,
Figure
5
5 6 7
8
9 10 11 12
1
2
3 L, 5 6
7 8 9 10 11 12
Annual variation of mean monthly precipitation
(6 year mean: 1975-1980).
U n i t : mm
-218-
amounts of precipitation in the lower Midland are much less than those
in the southern foothills. In the lower Midland, precipitation falls from
evening through night-time and night-time showers dominate in August and
September (Nishioka,1985). During our survey period in September 1985,
precipitation at Thimphu mainly fell from evening through night-time.
Yasunari and Inoue(1978) show the difference of the features of
precipitation between Shorong Himal and Khumbu Himal. Two of them are
as follows; "One is that the total amounts of precipitation are 4 or 5
times larger at Shorong and Glacier EB 050 stations than at Lhajung station. Another is that at Shorong and Glacier EB 050 stations, the
precipitation is concentrated during the daytime, while at Lhajung station
it is concentrated during the evening through nighttime". They analyzed
the causes of difference as follows; "The precipitation of a broader scale
in Shorong Himal may be caused by the convective instability
released
by forced uplifting of the conditionally unstable air of the lower troposphere from the Indian Plain along the southern slope of this mountain
range. On account of this "barrier effect" of Shorong Himal and also
Hinku Himal on the moisture supply, a semi-arid climate may appear in
the Khumbu region, which is located on the lee side of Shorong and
Hinku Himals. However, around the rocky peaks or ridges of 5000-6000m
in the Khumbu region, the relatively large amount of precipitation may
be provided by the cumulus convection induced by the heating of the
rocky ground by strong solar radiation".
Might the conditions of precipitation in the Nepal Himalayas shown by
Yasunari and Inoue(1978), above-mentioned, to correspond to those in the
Bhutan Himalayas? With regard to the topographic situation, the Bhutan
Himalayas are significantly different from the Nepal Himalayas. The area
of the High Himalaya is larger in the Bhutan Himalayas than in the
Nepal Himalayas. In the High Himalaya of Bhutan, two ranges extend
from west to east and the distance between them is larger than the distance between the Shorong-Hinku Himals and Khumbu Himal in the High
Himalaya of Nepal. Though the topographic conditions are different in the
Bhutan Himalayas and the Nepal Himalayas, the altitudes of peaks in the
southern High Himalaya of Bhutan are over 5000m and the climatic conditions in the lower Midland, between the two ranges in the High
Himalayas of Bhutan, may be similar to those of Khumbu Himal. Therefore, the difference in precipitation processes shown by Yasunari and
-219-
Inoued978) in the Nepal Himalaya may be one of the causes why the
period of maximum monthly precipitation occurrence is different
in
the
southern foothills and the lower Midland.
CHARACTERISTICS OF TEMPERATURE AND
TEMPERATURE LAPSE RATE
The observed temperature data are available in Bhutan at only
three stations. Therefore, the author intends to estimate
temperature
using data for regions around Bhutan. The data used here are from 16
stations in India and China(Fig. 6 and Table 1). Temperatures are estimated for the relations between temperature and altitude(Fig. 7 and
Data 3). The relations between the observed temperature and estimated
temperature are shown in Fig. 8 and show a good correspondence, in particular, at Paro. The only problem is the data for April at Phuntsoling.
The estimated temperature is lower than the observed one. The northern
part of India in April is in a period just before the
rainy season and
records high temperatures. The observed data at Phuntsoling is not necessarily abnormal. On the other hand, temperatures recorded at Assam are
not as high as in the Gandis Plain and the precipitation around Assam is
more than 100mm in April. The estimated data is not necessarily abnormal. Therefore, on the basis of the data used here, it is difficult to
determine which data is wrong. It is necessary to collect more data
along the southern foothills of the Himalayas.
The data for estimated temperature tend to be high compared with
the observed one at higher altitudes, in particular, in winter. The estimated temperature is shown in Fig. 9. This estimated temperature is
lower in winter and higher in summer in the higher altitudes compared
with that of Mitsudera and Numata(1967) in Nepal.
The annual variation of estimated temperature lapse rate is shown
in Fig. 10. The temperature lapse rate is large in winter and small in
summer, the largest being in December (0.622C/100m) and the smallest in
July (0.424C/100m). The annual temperature lapse rate is 0.544C/100m.
The temperature lapse rate is, in general, considered to be around
0.6C/100m.
Why is the temperature lapse rate small in summer? In
summer, on account of cumulus convections in the Himalayas, the air is
-220-
40
9
30
o
10O,I
I IO
ü
°
13
15.
2o
3o
20
80
90
NO.
Station Name
1
2
Dibrugarh
Gauhati
Cherrapunji
Kantsu
Xichang
Tech'in
Kunming
Lants'ang
Nachu
Tingen'ing
Qamdo
Lhasa
Shigatse
P'ali
Chiulung
Litang
3
4
5
6
7
8
9
10
11
12
13
U
15
16
Figure
6
100
Latitude
27
26
25
31
27
29'
06'
15'
38'
53'
28 39 t
25 01 '
22 34'
31
31
31
29
29
27
110
Longitude
95 01 '
91 35'
91 44'
99 59'
102 18'
99 10'
102 41 '
29'
25'
99 56'
92 03'
95 36'
11 '
96
42'
13'
44'
28 59'
30 00'
5 9
t
91 08'
88 55'
89 05'
101 33'
100 16'
Altitude(m)
106
55
1313
3394
1591
3589
1891
1055
4507
3873
3240
3658
3836
4300
2987
3949
Distribution of stations for temperature lapse rate.
-221-
CO
30 J
ANNUAL
r=-0.9855
y=-O.OO5l»Ux+2U.951
20 .
(D
rt
10 I
E
EH
-10
-20
1000
2000
3000
4000
5 000 (m)
Altiutde
Figure
Table 1
Temperature lapse rate on the basis of
annual mean temperature
(10 year mean: 1971-1980).
Temperature lapse rate around the Bhutan Himalaya.
Month
Temperature
lapse rate
Regression curve
January
February
March
April
May
June
July
August
September
October
November
December
0.615
0.604
0.611
0.568
0.500
0.438
0.424
0.438
O.476
0.545
O.6O6
O.622
y=-0.00615x + 18.153
y=-0.00604x+20.281
y=-O.OO6i1x+24-O59
y=-0.00568x+26.i60
y=-O.OO5OOx+27.333
y=-0.00438x+27.823
y=-0.00424x+28.123 "
y=-0.00438x+28.109
y=-0.00476x+27.480
y=-O.OO545x+25.711
y=-0.00606x+22.586
y=-0.00622x+19-057
Annual
0.544
y=-O.OO544x+24-951
-222-
PHUNTSOLING
30 -
u 20
Ui
cc
< 10
cc
ai
CL
UJ
»—
o-
-10 -
J
F
M
A
M
J
J
A
S
30 -
u
O
N
MONTH
D
PARO
20
ÜJ
ce
< 10 cc
UJ
CL
uJ
t—
0 -
-10 -
J
Figure
8
F
M
A
M
J
J
A
S
O
N
MONTH
D
Comparison between observed and estimated monthly temperatures.
-223-
1000
Figure
9
2000
3000
4 000
5000
6000
Altitude
Estimated altitudinal distribution of monthly temperatures.
1.0
— 09
o
o
~ 0.7LU
•—
<r 0 . 6 LU
1/1
0.5-
< 0. 3-
Q:
Lu
a.
2 0.2 -I
LU
0.1
1
J
1
F
1
M
1
A
1
M
1
J
1
:
J
1
1
A
1
S
O
1
N
Month
Figure 10
Annual variation of temperature lapse rate.
-224-
1—
D
well mixed vertically. The release of latent heat by cumulus convections
increases the temperature in the lower and middle
troposphere. In valleys of higher altitude, clouds develop mainly during the night-time and
during the daytime the solar radiation is not disturbed compared with low
altitudes. These conditions are expected to make the temperature lapse
rate small in summer.
The regional representative temperature is, in general, more reliable
than that of precipitation. The estimated temperature shows good correspondence with the observed one also in this paper. However, in mountain regions, the distribution of temperature is thought to be also complex as is that of precipitation, in particular, that of minimum temperature. It is necessary to observe the temperature at more stations on a
smaller regional scale and shorter time scale.
REGIONAL VARIETY OF MOISTURE CONDITION
Bhutan is located north of Assam, which is well known as a region
with one of the highest levels of precipitation in the world. On the other
hand, dry conditions exist in the bottoms of valleys of the lower Midland
and have already been reported (Schweinfurth, 1957). These dry valleys in
Bhutan are considered to be strange phenomenon in the moist eastern
Himalayas and ,in general, this phenomenon is called "Troll effect". In
order to clarify the moisture conditions in these dry valleys, it is necessary to show
the precipitation and evaporation. In Bhutan, precipitation
is observed, but data for evaporation is not observed operationally. The
climatic data using the calculation of evapo-transpiration is only temperature in Bhutan and the method of calculating evaporation using only temperature data is Thornthwaite's method(Thornthwaite, 1948). Although there
are many problems in Thornthwaite's method(Thornthwaite, 1948; Kayane,
1973),
the author calculates the potential evapo-transpiration using
Thornthwaite's method.
Potential evapo-transpiration based on observed temperature data is
shown in Data 4 and that using estimated temperature is also shown in
Data 5. The summary of all stations is shown in Table 2. In the southern
foothills and the southern High Himalaya facing Assam, the
annual
precipitation is much larger than the annual potential evapo-transpiration
-225-
Table 2
st
at i
Comparative moisture data of Bhutan.
0
n
a t i 0 n)
P h unt s 0 1i ng
P a r 0
T h i mP h u
(Ob
s e r
P o t e n t ial
e v P.
( mm
f
P r e e i oP n- Wa t e
r p lus
i t; a t
mm
( mm
er
cfiî
(m m)
Moj
l
s ure
n ex
S
C1 ima t i c
t ype
V
t i ma t i 0 n )
Sa r bha ng
S a mc h i
P ag 1i
P hun t s 0 1i ng
M0 n g a r
Ta s h i g a ng
Wa n g d h u P h o d r a n g
S h e mg a n g
130 6
6 8 9
6 2 1
4222
1 197
118 6
1 18 6
1 18 6
94 7
93 4
84 3
8 40
80 8
80 8
80 7
7 9 6
6 94
66 9
6 57
63 3
40 2 0
425 1
39 16
4222
5 18
70 2
57 9
1 48 9
1 47 2
1060
1 44 8
3100
1 28 0
63 4
5 97
7 30
63 4
597
2 969
0
6
53
55
30
2 866
3 1 48
27 55
3
3
5
9
429
232
264
0
0
3 2
28
2 8
0
3 6
60
0
2 24. 9
- 4. 8
- 1. 9
AA' r a '
Cl B 1 ' d a '
Cl B I' d a '
23 9.
2 6 1.
23 1.
2 56.
- 27 .
- 14 .
- 18.
7 7 .
8 2.
3 2.
80 .
290 .
84 .
- 3.
- 5.
15.
AA' r a '
AA' r a '
AA 1 r a AA' r a '
DB3' d a '
C1B3 1 da'
C1B2 ' da'
B3B2 1 r a '
B4B2 ' r a '
B1B2 ' ra'
B4B2 ' ra'
AB2' r a '
B4B1 ' ra'
C1B1 ' da'
C1B1 1 da'
C2B1 ' r a '
(Es
Ch u k ha
G 0 mP h u
Ch i r a ng
Dh
To
Pa
Th
Bh
a bhu1akha
ng s a
r
0
i mP h u
u mt h a n g
3 0 55
0
0
0
6 49
664
284
669
23 32
586
1
0
97
3
8
2
1
4
2
0
6
2
9
8
3
2
7
8
9
4
1
5
3
and the water surplus exceeds 2000mm. Monthly precipitation is more
than the monthly
potential evapo-transpiration during April through October and the period of water surplus mainly continues from May to October, though a little water deficiency occurs around March.
On the other hand, in the valleys of the lower Midland, except in
the central part, the annual potential evapo-transpiration
exceeds the
annual precipitation and the water surplus is nearly 0mm. The water
deficiency is great in the eastern part(Tashigang
and Mongar) and at
Wangdhu Phodrang, and the altitudes of these three stations are between
1000-1500m, which are less than that of the western part. In particular,
at Mongar, monthly precipitation is less than monthly potential evapotranspiration throughout the year and the conditions of water deficiency
also dominate throughout the year. The annual water deficiency reaches
429mm. At Tashigang and Wangdhu Phodrang, the annual water deficiency
is nearly the same amount, around 250mm, and less than that of Mongar.
The monthly precipitation is less than the monthly potential evapotranspiration except in July at Tashigang and in July and August at
Wangdhu Phodrang, and the condition of water deficiency continues from
November through January to June.
In the. eastern part(Paro and
Thimphu), as the altitude is high, between 2000-2500mm, the temperature
is lower than that of the eastern part and the potential evapotranspiration is also lower than that of the eastern part. The annual
water deficiency is around 50mm. The monthly precipitation exceeds the
monthly potential evapo-transpiration from June to September at Paro and
from July to September at Thimphu, and the water deficiency occurs in
May at Paro and continues from April to June(mainly in May) at Thim;
phu.
In the central part of the lower Midland, the moisture
conditions
are different at Tongsa and at Bumthang. At Bumthang, the annual
precipitation(730mm) is more than that of the eastern and western parts
of the lower Midland and the water deficiency indicates 0mm. However,
the water surplus and the moisture index are lower than those in the
southern High Himalaya and the southern foothills. The moisture index
and the climatic type at Bumthang are close to those of the eastern and
western parts of the lower Midland rather than the southern High
Himalaya.
On the other hand, at Tongsa, the values for precipitation
water surplus, water deficiency ,and moisture index are very close to
-227-
those of the southern High Himalaya. The climatic type is also
similar
to that of the southern High Himalaya. The moisture conditions at Tongsa
are considerably different
from the other
and Tongsa is the wettest town in
In the
southern
stations in the lower Midland
the lower Midland.
High Himalaya,
the
water
surplus
exceeds
water deficiency ,and at Gomphu and Chirang the water deficiency
the
oc-
curs around April.
Thornthwaite's climatic classification
on the basis of the moisture
index together with their limits are as follows:
Climatic Type
A
Perhumid
B
Humid
4
B
3
B2
Moisture Index
100 and above
80 to 100
60 to 80
Humid
Humid
40
20
0
-20
to
to
to
to
60
40
20
0
l
D
Humid
Moist subhumid
Dry subhumid
Semiarid
-40 to -20
E
Arid
-60 to -40
B
l
c2
C
On the basis of these data for moisture index, the stations in the
southern foothills belong to the Perhumid climatic type(A type)
and
those in the southern High Himalaya to the Humid climatic types(B^-Bj
types). On the other hand, in the lower Midland, the Dry subhumid
climatic type(Cj type) and Semiarid
climatic type(D type) appear. The
moisture index at Mongar
indicates -22.6 and this value belongs to the
Semiarid climatic type. The Dry subhumid climatic type appears at three
stations! Tashigang, Thimphu and Paro). With regard to the above results
using
Thornthwaite's climatic classification, in the valleys of the lower
Midland except the central part(in particular at Tongsa),
dry conditions
dominate locally. Considering the distance between the southern foothills
and the lower Midland(less than
lOOKm), abrupt changes in moisture
conditions ranging from the Perhumid climatic type(A type) to the Dry
subhumid climatic type(Cj) or the Semiarid climatic type(D type) appear
from
the southern foothills to the middle reaches, except in the central
part of Bhutan.
-228-
CONCLUDING REMARKS
The climate of Bhutan has not been clarified
before,
as already
mentioned, and Bhutan is one of the most unknown areas in the world.
Therefore, in this paper, the author mainly analyzes
the distribution and
seasonal changes of basic climatic elements(precipitation, temperature etc.)
and shows the general features of Bhutan's climate. Since climatic data
are not fully available in Bhutan, the climatic factors which dominate the
distribution and seasonal changes of climatic elements cannot
be
fully
analyzed.
In Bhutan, there are many important and interesting problems
left,
in particular, with regard to the regional differences of climate. For example, does the onset of the summer monsoon occur at the same time
throughout Bhutan?
Study of the climate of Bhutan is still in its initial
stages and there are many problems which should be clarified.
ACKNOWLEDGMENT
I wish to express my gratitude to Prof. H. Suzuki, Department of
Geography, University of Tokyo for his guidance and encouragement. I
also wish to express my thanks to the members of our survey group and
Mr. K. Nishioka for his helpful advice. I also would like to thank Prof.
M.M. Yoshino
for kindly permitting the use of precipitation and temperature data in China, which were obtained by Prof. M.M. Yoshino
through the good offices of the Institute of Geography, Academic Sinica,
Beijing.
I used a HITAC
University of Tokyo.
M680-H
computer
in
the
Computer
Center,
REFERENCES
Eguchi, T. (1987a). Topographic features in the central part of Bhutan
Himalaya. (In this issue.)
Eguchi, T. (1987b). Synoptic- and meso-analysis of climatic onditions
in Bhutan during September through November in 1985. (In this issue.)
-229-
Karan, P. (1967). Bhutan. University of Kentucky Press, Lexington, 106p.
Kayane, I. (1973). Evapotranspiration of Monsoon Asia. Water balance of
Monsoon Asia, 55-70(in Japanese).
Mitsudera, M. and Numata, M. (1967). Meteorology of Eastern Nepal.
Jour. Coll. Arts & Sei., Chiba Univ., 5: 75-83.
Nishioka, K. (1985). Personal communication.
Ramage, C.S. (1971). Monsoon meteorology. Academic Press,
New York and London, 296p.
Schweinfurth, U. (1957). Die horizontale und vertikale Verbreitung der
Vegetation im Himalaya. Bonner Geographische Abhandlungen, 20: 1-373.
Thornthwaite, C. (1948). An approach toward a rational classification of
climate. Geographical Review, 38: 55-94.
Yasunari, T. (1976); Seasonal weather variations in Khumbu Himal. Seppyo,
38: 74-83.
Yasunari, T.and Inoue, J. (1978). Characteristics of monsoon precipitation
around peaks and ridges in Shorong and Khumbu Himal. Seppyo,
40: 26-32.
-230-
Data 1
Distribution of mean monthly precipitation in Bhutan
(6 year mean: 1975-1980). U n i t : mm
-231-
92"
APRIL
28*-
i
5i0 KM
KU
27'
-232-
92'
JUNE
23'
;
^°KM
wW\
-O
r
Ù
J
o '^
^
2T-\
92"
92"
AUGUST
28'-
J
KM
27'
-233-
92'
OCTOBER
28"
27-1
-234-
28-A
92"
DECEMBER
/
o
,
1
y
•S'
rr^f
'
,°KM
27'
92*
-235-
5
Data 2
Annual variation of mean monthly precipitation
(6 year mean: 1975-1980).
PHUNTSOLING
-1000
1000-
o
PAGLI
•8 0 0 -
-800
600-
-600
400
-400
2 00-
-200
•H
•P
•H
D,
o
u
1
2
3
U
5 6
7
8
2 3 4
9 10 11 12
5 6
7 8 9 10 11 12
Month
SARBHANG - 1 2 0 0
SAMCHI
1000-
-1000
&00-
-800
600-
-600
400-
-400
200-
-200
1 2 3 U 5
6 7 8 9. 10 11 12
1 2 3 4
-236-
5 6
7 8 9 10 11 12
DHABHULAKHA
DAMPHU
8 00-
-400
600-
-200
400-
1 2 3 4
5 6 7 6 9 10 11 12
GOMPHU
200-
-300
-200
-100
1
2 3 A
5 6 7 8 9 10 11 12
1
2 3 4
5 6 7 & 9 10 11 12
-400
400CHUKHA
SHEMGANG
200-
-200
1 2
3 4 5 6 7 8 9 10 11 12
1
DAGA
400-
200-
1 2 3 U 5 6 7 8 9 10 11 12
-237-
M5
2 3/.
5 6 7 8 9 10 11 12
PARO
200-
-200
MONGAR
100 —
-100
1
I
2 3 A
5 6
7 8 9 10 11 12
1 2
3 A
5 6 7 8
9 10 11 12
THIMPHU
200-
TASHIGANG
100-
-200
1
2 3 A
-100
5 6 7 8 9 10 11 12
1
WANGDI PHODRANG
200100-
1 2 3 A 5 6
7
8 9 10 11 12
TONGSA
300-
'200100-
1
2 3/.
5 6
7 8
9 10 11 12
BUMTHANG _
200100-
1
2 3/.
5 6 7 8 9 10 11 12
-238-
2 3 /.
5 6
7 8 9 10 11 12
Data 3
Monthly mean temperature lapse rate
(10 years mean: 1971-1980).
co
co
30
30 .
JANUARY
APRIL
r=-O-9866
y=-O.OO6l5x+l8.153
3
^^s.
y=-O.OO568x+26.l6o
20
(D
d)
E"«
10
10
0
-10
-10 .
-20
-20
1000
2000
3000
'000
S000(m)
1000
2000
3000
4 000
5 000(rn)
Altitude
('ci
30
FEBRUAÜÏ
r=-0.98
y=-0.0060»ix+20.28l
MAY
i^
° ^ ^ ^
r=-0.9788
y=-O.OO5OOx+27-333
20
10
0
-10
-10
-20
-20
1000
2000
3000
4000
1000
5000 (m)
2000
3000
4000
5000 (m)
CO
30 .
JUNE
r=-O.9T33
y=-O.00U38x+2T-823
MAKCH
r=-O.98!»T
y=-O.OO6lljt+2li.O59
20
20
10
10
-10
-20
-20
1000
2000
3000
4000
5000 (m)
-239-
1000
2000
3000
4000
5000 (m)
('O
CO
30
30 .
OCTOBER
JULY
r=-0-9681»
y=-0.00b2l<x+28.123
r=-0.99l8
y=-O.OO5l'5x+25.711
20
20
10
10
-10
-10
-20
-20
1000
2000
3000
4000
1000
5000 (m)
2000
3000
4000
5 000(m)
CO
30
NOVEMBER
AUGUST
r=-0.9898
y—0.00606x+22.586
r=-0.96o6
y=-0.O0li36x+28.1O9
20
20 .
10
10
-10
-10
-20
-20
1000
2000
3000
'000
1000
5000 (m)
2000
3000
«000
5000 (m)
CO
CO
30 .
30
SEPTEMBER
r—0.987 1 "
y=-0.00li76x+2T.lt8o
DECEMBER
r=-0.9839
y=0.00622x+19.057
20 .
10
-10
-20
-20
1000
2000
3000
'000
1000
5000 (m)
-240-
2000
3000
'000
5000 (m)
Data 4
Moisture data on the basis of observed climatological data.
Item
M
O
M
Precipitation
Storage
change
Storage
Actual
evap.
45
89
156
1 7
15 5
37
26
16 1
16 8
14 3
9
4 64
848
1 00 5
793
26
-8
-10
7
93
0
0
13
94
10 6
2 10
0
0
0
10 0
10 6
Ol
35
Ol
evap.
18
10
0
7
10 0
10 0
45
36
16 1
143
15 6
10 0
15 7
10 0
35
Ol
Potential
en
[Phuntsoling]
10 0
13 5
3
0
0
0
0
0
0
228
692
848
638
15
76
38
-3 8
62
48
13 0 6
30
4222
-18
44
76
48
12 53
0
0
0
53
9
10 4
0
0
2969
6 89
634
0
0
0
0
0
0
9
20
35
5 8
81
10 5
15 1
81
57
30
42
- 1 2
10 1
10 4
95
40
1 27
8 2
1 7
1 1
17
0
0
3
46
32
1
- 1 9
- 17
0
0
3
49
82
42
2 3
6
5 4
40
10 1
81
95
81
57
30
17
4
4 1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
72
48
-8
92
96
9 2
29
13
6 21
1 28
1 50
48
5
0
5 97
0
32
58
72
88
10
52
78
-4
-2 4
-13
0
0
32
90
96
72
59
6
78
96
9 2
1 00
72
52
29
13
591
16
0
14
0
0
0
0
0
0
30
0
0
0
6
0
0
0
6
4
en
deficiency
surplus
Ol
Water
Water
evap.
Precipitation
Storage
change
Storage
0
i3
47
-6
0
0
0
12
12
6
ï3
Water
deficiency
3
7
35
0
Water
surplus
0
0
0
Actual
evap.
10
-40
634
en
Potential
5
0
[Thimphu]
Potential
evap.
Precipitation
Storage
change
Storage
Actual
evap.
6
18
31
48
0
3
19
30
-6
-1 5
53
38
6
18
-1 2
26
31
0
0
Water
deficiency
0
0
0
Water
surplus
0
0
0
- 1 8
8
48
CJl
I
CS3
Ol
[Paro]
Data 5
Moisture data on a basis of estimated climatological data.
Item
M
O
M
A
[Sarbhang]
Potential
evap.
Precipitation
Storage
change
Storage
Actual
evap.
3 4
4 5
8 6
10 4
14 2
14 9
158
15 1
12 7
4
12
44
13 8
3 54
7 60
124 8
6 2 5
5 6 6
10 0
19 4
6 4
63
3 8
11
1 197
40 20
3 0
-3 3
- 10
3 4
6 6
0
0
0
0
0
0
-2 7
4 3
10
0
3 4
10 0
10 0
10 0
10 0
10 0
10 0
1 00
7 3
3 4
4 5
54
10 4
14 2
14 9
15 8
15 1
127
10 0
6 3
3 8
1 16 5
Water
deficiency
0
0
3 2
0
0
0
0
0
0
0
0
0
3 2
Water
surplus
0
0
0
0
14 6
6 1 1
10 90
4 7 4
4 3 9
9 4
1
0
2 8 5 5
3 3
4 4
8 4
1 12
13 9
14 7
15 6
14 9
9 9
6 1
1 18 6
4 2 5 1
[Samchi]
Potential
CO
evap.
Precipitation
4
4
15
194
4 4 9
6 9 4
108 9
87 7
12 5
63 9
23 3
5 2
3 7
1
2 9
-2 6
0
8 2
18
0
0
0
0
0
- 9
-3 6
2 6
0
0
8 2
10 0
10 0
10 0
10 0
10 0
10 0
9 1
5 5
13 9
147
156
149
12 5
99
6 1
3 7
CO
I
Storage
change
Storage
Actual
evap.
1 10 3
3 3
3 0
15
1 12
Water
deficiency
0
14
6 9
0
0
0
0
0
0
0
0
0
8 3
Wa ter
surplus
0
0
0
0
2 9 2
54 7
93 3
7 28
5 14
13 4
0
0
3 14 8
3 3
4 4
8 4
1 12
13 9
14 7
15 6
14 9
12 5
9 9
6 1
3 7
1 18 6
4
20
4 9
14 8
3 9 6
7 8 9
94 3
7 13
59 5
19 8
5 1
10
3 9 16
2 9
-2 4
- 10
3 6
64
0
0
0
0
0
- 10
-2 7
3 4
10
0
3 6
10 0
10 0
10 0
10 0
10 0
10 0
90
63
[Pagli]
Potential
evap.
Precipitation
Storage
change
Storage
3 3
4 4
5 9
1 12
13 9
14 7
156
14 9
12 5
9 9
6 1
3 7
1 16 1
Water
deficiency
0
0
2 5
0
0
0
0
0
0
0
0
0
2 5
Water
surplus
0
0
0
0
193
6 4 2
7 87
5 6 4
4 70
9 9
0
0
2 7 5 5
Actual
evap.
CD
CM
t-
CO
CM
co
CM
r-«
r H
co
in
r^ oo
oo o>
—i
m
-C
^
o
CM
O
•<t
CM
CM
CM
co
en
O
O
co
t-
r^
CM
O
co
r - i
• * #
t-t
t- o t- o t— o
co co I t- co
o
r-l
00
CO
t~
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CD
CO
CM
C-
CD
oo co o
o
t- •* o
CM
t^t
OO
O
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00
o o o o co o *-*
CO
f-
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co
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O
o
co in
CM
o
t
CM
CO
CO
O
CD
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t-
CM
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CO
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co
o
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r- t—
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CM
CM CM
t—
en
oo
f-
t-
t-
CM
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co »-* in o
co I in o
O
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r-i
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t-H
CM
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co
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o
CM
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co
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lO
rH
iH
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CO
CO
O
CO
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co
o
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r-i
r^
r-t
i-i
co
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in o
o
o
m
r-i O
^H
T-t
m
co
c~
00
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T-H OO
co
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r-i
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't o
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^t
r-l
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CM
CO
t- O
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CO
CD
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T-H
co
CM
o co
•**•
i-l
o
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co m
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T-l
CM
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CD
CD
CM
in
in
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co
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00
CO
m
co o
t—
CM
o
O
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•-' CO
t— m
O
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c~ in
iH
co o
•—' •—* co o
o
CM
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CD
CD
O
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r-< CD
CM
o
i-(
^H
m
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CD
—
in
CM
CM
CO
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co
o
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r~
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oo
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n
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co
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r~
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en
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eu
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eu
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-243-
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-248-
of the Bhutan Himalaya.1987.
Chiba University.
SYNOPTIC- AND MESO-ANALYSIS OF CLIMATIC CONDITIONS
IN BHUTAN FROM SEPTEMBER THROUGH NOVEMBER IN 1985
T. EGUCHI
Department of Geography, Faculty of Science
University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113,Japan
ABSTRACT
On the basis of climatic observations made during a
trekking survey in 1985, the author intends to clarify the
climate of Bhutan on synoptic- and meso-scales. The survey
period is from September through November and this period is
expected to be the transition period from the summer monsoon
period to post-monsoon period.
In 1985, the seasonal change from the summer monsoon
period to the post-monsoon period occurs around October 19 in
Bhutan. This change occurs
just after the passage of tropical
cyclone from the Bay of Bengal.
The diurnal variation of temperature is more obvious
during the post-monsoon period than during the summer monsoon
period. The temperature lapse rates indicate diurnal variation
and show a maximum in the early morning and minimum in the
daytime, in particular, around noon.
The valley wind in the high altitudes is well developed
during the daytime, however, the mountain wind is not well
developed. In the lower Midland, though the mountain wind is
observed during the early morning, it is not well developed.
This mountain and valley wind system is closely connected with
the diurnal variation of precipitation.
-249-
INTRODUCTION
Our trekking survey in 1985 was mainly done in the central
part
of Bhutan(Fig. 1) for a period of around three months., from September
to November. The number of meteorological stations
is around 50 in
Bhutan and the observed climatic elements are
mainly temperature and
precipitation. There are few stations in the northern High Himalaya, and
winds are observed at a few stations. Therefore, during our survey period,
the author observed temperature, wind and weather. Using observed data,
the author intends to clarify the climatic condition in Bhutan on a smaller scale than synoptic, which has never been analyzed before.
At first, this period is expected to be the transition period from
the summer monsoon period to the post-monsoon period . In the Nepal
Himalayas, Yasunari(1976) analyzed the seasonal weather variation on the
basis of the observational data from Lhajung station in the Khumbu
Himal and pointed out that the seasonal change from the summer monsoon period to the post-monsoon period occurs in October. During our
survey period, the weather conditions changed in October. Therefore, the
author
analyzes the weather mainly in October in order to clarify the
seasonal change from the monsoon period to the post-monsoon period in
Bhutan.
Secondarily, the author analyzes temperature data in order
to
clarify the temperature conditions on a meso-scale mainly in the central,
part of Bhutan. In particular, the diurnal variation of temperature lapse
rate and the relationship between the
temperature lapse rates, the
seasonal changes and the topographic conditions are discussed.
Finally, the author intends to clarify the wind conditions
in
Bhutan. The air circulations in Bhutan have not been reported using the
data. In this paper, the features of local circulations and their seasonal
changes are mainly shown.
SYNOPTIC ANALYSIS OF SEASONAL CHANGE
FROM MONSOON TO POST MONSOON
Fig. 2 shows the maximum and minimum temperatures at Thimphu
(Taba) and the weather conditions along the survey route.
-250-
The bottom
a 9'JO'
Survey
route
BMI Cl.A J
Dl.SII'î.»
C-i
•28"O'
• 27'O"
n'o'
Figure 1. Route map of scientific expedition in 1985.
CC)
30
MAXIMUM TEMPERATURE
20
10
MINIMUM TEMPERATURE
-10
WEATHER
16
SEPTEMBER
1012 K
18
OCTOBER
25 26
1
5
8
NOVEMBER
Figure 2. Temperatures at Taba(Thimphu) and weather conditions
during the survey period(from September 16 to
November 16,1985).
-251-
lines indicate the weather conditions, which show that the precipitation
phenomena occur at least once a day along our survey route. Therefore,
the weather was observed at different
stations almost every day.
The weather condition changes around October 2 and October 19.
Before October 2, from September 16 to October 1, the weather shows
clear diurnal variation. As our survey route is along the bottoms of valleys, during this period, precipitation is mainly brought about during evening through night-time every day. However, after October 2, the weather
does not show clear diurnal variation and fine weather dominates all day
long for a few days. The minimum temperature at Taba drops on October
2 and a drop of temperature at OOz also occurs at Gauhati in India and
at Pa'li in China around October 2(Fig. 3 and Fig. 4). At Gauhati and
Pa'li, the pressure reaches its maximum on October 2. Around Bhutan,
temperature drop and maximum pressure occur on October 2. The
fine
weather on October 2 is considered to have arisen from the anticyclone
extending from the west. On the 500mb weather charts, the anticyclone,
centered at (30N, 60E), extends from west, and the isohypse of 5880m
reaches 80E on October 1 and 90E on October 2. On the surface weather
charts, though the surface anticyclone is not clearly recognized, pressure
is relatively high
at all stations around Bhutan(Fig. 5). On the other
hand, after this fine weather, cloudy or rainy weather prevails continually
from October 6 to 18. During these days, at least three tropical disturbances invade the Indian Subcontinent
from the Bay of Bengal and the
Arabian Sea(Fig. 6), and at least
one western disturbance in the midlatitudes passes through the
Himalayas. The rainy days mainly occur
around October 8 and October 17 in Bhutan and precipitation distribution
is affected
by these disturbances(Fig. 7). In order to clarify the
relationship between rainy days in Bhutan and the disturbances
abovementioned, the author analyzes the 500mb and surface weather charts.
On October 8, a western disturbance passes around the Tibetan
Plateau and the Himalayas(Fig. 8) and the tropical
disturbance invades
from the Arabian Sea. In Bhutan, precipitation occurs mainly on October
9 or October 10. The tropical disturbance is recognized on both surface
and 500mb weather
charts. This disturbance invades the Indian Subcontinent on October 8 and moves northeastward(Fig. 6 and Fig. 8). Both
disturbances are expected to affect the rainy or cloudy weather around
Bhutan during this period. However, as the period that the western dis-252-
Li
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Dew Point Temperature
SEPTEMBER
42410
OCTOBER
2610
9158
NOVEMBER
51
Figure 3- Variation of climatic data at Gauhati in India
from September through November in 1985.
-253-
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70-E
J
80-E
OCT.
2
90-E
30-N
2O"N
IO-N
70-E
80'E
9 0-E
Figure 5. Surface and 500mb weather charts during October 1-3,
1985 (12GMT).
Right: Surface (ex. 2 indicates 1002mb).
Left : 500mb
(ex. 582 indicates 5820 gpm.).
-255-
30°N
20°N
7O'E
80'E
9O'E
Figure 6. Route of tropical disturbance and cyclones
-256-
Figure 7- Weekly precipitation around India in 1985
-257-
M
p
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lût.
sot
20"N
° \
)
f\
OCT.
OCT. 7
I O-N
70"E
80"E
A
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9 O-E
5OE
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70"E
MO
JOE
9OE
HOE
9O-E
SOE
3O-N
'OE
90E
HOE
2O*N
70"E
9O-E
Figure 8. Surface and 500mb weather charts during October 7-9
1985 (12GMT). Signs are the same as Figure 5-
-258-
turbance passes around the Himalayas occurs at almost the
same time
as the period that the tropical disturbance invades
the Indian Subcontinent, it is difficult to discern which disturbances
largely affect the
rainy or cloudy days around October 9 in
Bhutan. The amount of
precipitation during this period is not as
great as around Bhutan and
less than the precipitation in the northeastern part of India and Nepal.
During this period we pass
Juree-La(pass), with an altitude of around
4700m, and at that time it is rain, and not snowfall that we encounter.
Therefore, these disturbances are not expected to bring about the first
snowfall accumulation on the ground in the Bhutan High Himalaya.
On October 12, the tropical cyclone invades the Indian
Subcontinent and runs through westward of Bhutan(Fig. 9). Although the cyclone
may bring much precipitation or snowfall in the western part of the
Himalaya, it is considered that the cyclone does not largely affect the
weather in Bhutan, because its route is about 10 degrees west of Bhutan
and the pressure around Bhutan does not show the clear minimum value
as the cyclone follows.
Around October 17, the cyclone passes around Bhutan(Fig. 10). This
cyclone originates in the Bay of Bengal and reaches West Bengal on October 17. This cyclone is evidently recognized on the 500mb charts from
October 14 and recorded 5670 gpm at 12z on October 15. On the basis
of the observations made between Bumthang and Mongar in Bhutan(Fig.
1), the rainy or cloudy weather continues from the afternoon of October
15 to the morning of October 18. In this region, the cyclone produces
rainfall
without the diurnal variation. On the other hand, in the regions
with altitudes of at least more than 5000m in the northern Bhutan High
Himalaya, this is the first snowfall accumulation on the ground. Just
after the passage of this cyclone, fine weather dominates and this is a
drop in temperature at many stations in and around Bhutan and pressure
rises at Pa'li and Gauhati(Fig. 2, Fig. 3, Fig. 4). In particular,the pressure at Gauhati,
located in Assam south of the Himalayas,
rises
remarkably. The upper air data at Calcutta shows the continuous westerly
at all
strata from October 19 and its speed is greater than before(Fig.
11). The value of dew point depression indicates more than 15C at 12Z
on October 19 at 850mb and 700mb.
On the basis of the observation made in Nepal in 1973 and 1974,
Yasunari (1976) points out that the monsoon weather pattern ended
-259-
7OE
9OE
MOE
,-8
^
A
20"N
)
I O-N
7O*E
\
8
6
OCT. 10
,-
7OE
9O'E
5OE
3O'N
7OE
9OE
MOE
20'N
IO-N
7O'E
80'E
90'E
5OE
80-E
7OE
9OE
HOE
90-E
Figure 9- Surface and 5OOmb weather charts Juring October 10-12,
i-igure y.
Mor.MTÏ. Siens are the same as Figure 5-
-260-
5OE
_-^
—
90E
HOE
-6
\
r
2 O-N
70 E
vç
m
576
-^
W
V5&8-
\
OCT.
10-N
70'E
80-E
OCT.
16
16 /
V
. 90*E
30'N
70 E
90E
70 E
90E
2CTN
10-N
70'E
80"E
1
50E
HOE
II'
l/ll
6
•.
30-N
2 O-N
ü!!!!!!!!!!^
•
Cl
10-N
70-E
\
J
80*E
OCT.
OCT.
18
^
18 I
90*E
Figure 10. Surface and 500mb weather charts during October l6-l8,
1985 (12GMT). Signs are the same as Figure 5-
-261-
f t 1f
I
150
200
r f^ \
250
f
J
• J J J
X
300
U
I
CO
CO
I
k
1
2
3
4
5
6
7
8
9
10
11
12
13
\U
15
16
17
18
19
20
21
22
Figure 11. Variation of upper winds at Calcutta(October I-25.1985).
Isoline indicates dew-point depression( q C).
23
Jr
24
25
.5 m/s
Y—\
m/s
abruptly with the first arrival of a westerly disturbance, associated
the Sub Tropical Jet Stream, which brought about the first snowfall
cumulation on the ground and just after these days of snowfall
weather changes entirely to the post-monsoon type. In 1985, the
snowfall accumulation on the ground in Bhutan occurs just after the
sage of the tropical cyclone.
with
acthe
first
pas-
On the basis of the above climatic conditions in and around
Bhutan, the seasonal changes from the summer monsoon period to the
post-monsoon period around
Bhutan are considered to occur around October 19, 1985 and this change occurs just after the passage of the
tropical cyclone from the Bay of Bengal. Further study is necessary as to
whether the seasonal change from the summer monsoon to the postmonsoon period in 1985 applies to other years and whether the period of
this change is same in the Himalayas or different between the western
part and the eastern part.
DIURNAL VARIATION OF TEMPERATURE
IN THE CENTRAL PART OF BHUTAN
In this section, the author mainly discusses the diurnal variation of
temperature as observed in data taken during our survey period. Temperatures are observed every three hours along our survey route between
150m and 5300m, though temperatures are observed at different stations.
The minimum temperature is -5C observed at 00Z on October 3 at
Tsoreim(5200m). The maximum temperature is 27C observed at 06Z on
October 27 at Manas(140m). The temperature largely varies in accordance
with the topographic and weather conditions, and the seasonal variation is
expected to be large (Fig. 2). As the data of temperature are observed
at different stations and temperature data for three or six hour periods
are not available in Bhutan, temperature data are reconstructed from the
data for Gauhati in India, i.e. the differences between the observed data
and those at Gauhati.
Figs. 12 a-d show the scatter diagrams for temperature
differences
by altitude taken every six hours (00Z, 06Z, 12Z, 18Z). 00Z, 06Z, 12Z,
and
18Z indicate 06,
respectively.
12,
18,
The temperature
and 24 Standard Time in Bhutan(BST),
lapse rate on the basis of the data of
-263-
( A ) 00GMT
-401000
2000
3000
4000
5000(m)
Altitude
('O
10-1
(B)06GMT
0-
-10-j
-20H
-30-j
-401000
2000
3000
4000
5000(m)
Figure 12. Scatter diagram of temperature difference between
Gauhati and observation points of Bhutan.
(A) 00GMT (B) 06GMT (C) 12GMT (D) 13GMT
-264-
( C)
(C)12GMT
10-1
0-
-10-
-20-
-30-
-1,0-
—i
1000
1
2000
—l
3000
( o
1
4000
1
5000(m)
(D)l8GMT
»o-I
0-
-10-
-20-
-30-
-UO-
1000
2000
3000
-265-
4000
5000(m)
temperature differences is larger at OOZ (0.586C/100m) and smaller at
O6Z (0.463C/100m). The temperature lapse rate is expected to be larger
during the period between mid-night and early morning and smaller around
noon, and in fact does show the clear diurnal variation. The mean temperature lapse
rate of four times indicates 0.523C/100m. This value is
nearly equal to the monthly mean temperature lapse rate in October by
Eguchi(1987).
However, the difference between the observed and estimated
temperature data is larger than those of mean monthly data(Fig. 13). The
mean difference between the observed and estimated temperatures is
1.69C at 00z(51 days) and 1.87C at 06z(40
days), and this mean difference is larger at 06Z than at OOZ. The data at both times are largely
affected by weather conditions. At OOZ, the estimated temperatures are
generally lower than the observed temperatures, in particular, in the
higher altitudes or during the summer monsoon season. On the other
hand, during a few days after the retreat of the summer monsoon
(October 19-22), the estimated temperatures are higher than the observed
temperatures. After the passage of the cyclone, as already mentioned in
section 2, a drop in temperature occurs on October 19 in the
Bhutan
High Himalaya. However, in Assam it occurs on October 24 on the basis
of the data at Gauhati. Therefore, the differences
are large during this
period. At 12Z, though the obvious seasonal features are not recognized,
the temperature is largely affected by the weather conditions rather than
the data at OOZ. The estimated temperatures are larger than the observed temperatures for the cloudy or rainy days and the reverse differences occur in the fine days. The percentage of estimated temperatures which differ from the observed temperatures by less than 2C is
around 70% at OOz and 06Z.
The diurnal temperature difference between the data at OOZ and
06Z is observed for 19 days at the same stations. The largest temperature difference is recorded on November 16 at Thimphu and its value is
14.2C. In the higher altitudes above 3000m, the difference is lower than
expected. In the fine days, for example on October 3, the difference
reaches 12.5C, however, on the other days the differences are around 5C.
In particular, on September 28, its value is only 1.4C at 4920m. The estimated
diurnal differences on the basis of the estimated temperatures
are shown in Fig. 14. As the estimated temperatures include the above-266-
6000-
10
NOV
(A)
CL)
u
<Ü
16
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4 c< ; _
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16 20
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•
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—
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Figure 13- Difference between observed and estimated temperatures.
(A) 00GMT (B) 06GMT
(upper) Altitude of observation point,
(lower) Temperature difference(estimated minus observed)
-267-
I—I—I—I—I
16
15-
I
I—I—I—|—I—I—I—I—|—n—I—i—|—I
I—i—I—1—I—I—I—i—|—l—I—I—r—|—I—I—I—I—|—I
16
20
25
SEP
12-
U
IN3
Oi
00
5
a
u
6
9-
I"
^
3 -
Observed
Estimated
(Km) 6 5•H
-P
U
3
2
1
-
Figure 14. Diurnal Difference of temperature.
(upper) Estimated diurnal difference of temperature by altitude,
(middle) Diurnal difference of observed and estimated temperatures.
(Lower) Altitude of observation points.
mentioned problems, the relationship between the estimated and observed
temperatures is not necessarily a good one.
The data for diurnal variation of temperatures shown in Figs. 15-20
were mainly recorded in the higher altitudes. The temperature varies with
the weather conditions. In Figs. 15-20, the maximum temperature occurs
between 9 and 12 BST., because the weather worsens in the afternoon.
The temperatures in Figs. 15-19 are observed before the retreat of the
monsoon, i.e. during the summer monsoon season. On the other hand, in
Fig. 20, at Kurthang the daily maximum temperature is recorded around
15 3ST. Since these data for Kurthang are recorded after the retreat of
the summer monsoon, the weather is fine all day long. The temperature
drops considerably just after sunset and does not vary significantly during
the night-time. The temperature reaches its daily minimum at around 06
BST. in the early morning, and just after sunrise the temperature increased greatly, in particular, on fine days.
LOCAL CIRCULATION IN THE BHUTAN HIMALAYAS
The wind data for the same stations are shown in Figs. 15-20. At
stations in the northern Bhutan High Himalaya(Figs. 16-19), the
valley
wind is dominant. The valley wind is mainly dominant from 09 BST. to
18 BST., while, during the night-time through the early
morning, calm
condition are dominant. The mountain wind is not necessarily observed.
On the other hand, in the lower Midland of the Bhutan High Himalaya,
the mountain and valley wind system is recognized. In particular, at Kurthang, the mountain and valley wind system is obviously observed, though
the wind speeds are not so great.
Inoue(1976) described the mountain and valley wind system in
Nepal and found that, during the summer monsoon season, the valley wind
is dominant and the mountain wind is not well developed. In Bhutan, the
same features are recognized at least during the summer monsoon season
in the higher altitudes(the northern Bhutan High Himalaya). However, in
the lower Midland, the mountain and
valley wind system is recognized
during the summer monsoon season, though the amount of available data
is limited. Further studies are necessary regarding the problems of
regional difference in local wind systems.
-269-
""-0.5 m/s
•o Temperature
"^ Dew-point temperature
15-
•a Relative humidity
cu
f-l
I
to
-J
o
I
O
0
•p
CO
10-
Fine
Cloudy
a
CD
Rainfall
Snowfall
O
1
18
Sep.
i
'
•
i
21
0
16
1
'-
-,
1
3
Fog
r -~ " — 1 — " ~ - i — | — i — i—(—i—
6
9
Sep.
12
-"—r
15
18
17
Figure 15. Climatic elements observed at Dochu-La(3120m).
J
j
y
20-
(ü
U
15-
-100
CD
M
fU
ct
H<
I
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0)
CD
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10-
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50
|
A
PH«
ct
0
18
r
21
Sep. 18
0 i
0
9
12
15
18
i
21
Sep. 19
Figure 16. Climatic elements observed at Nikkachu(258Om)
Signs are the same as Fig. 14.
0
Sep. 20
y
15-
- 100
CD
M
P>
et
H-
-P
CÖ
CD
U
to
10-
50 3*
to
c
I
HH-
a.
et
1
9
•
i
1
12
15
'
I
i
18
Sep, 21
21
6
Sep. 22
Figure 17. Climatic elements observed at Morathang(3580m)
Signs are the same as Fig. 14.
-100
10D—D...
•
•-a
0)
-a
CD
ci-
H-
-P
I
U
INS
a
00
I
- 50
5-
ET
C
3
HD,
H'
E-*
ci-
©©
18
21
Sep. 24
12
15
18
21
Sep. 25
Figure 18. Climatic elements observed at Tsongtsothang(4340m)
Signs are the same as Fig. 14.
3
6
Sep. 26
O)
u
5-
-100
0-
- 50
3
tö
SH
O)
a
E-i
CD
©
-5
18
21
15
O
CD
i
r
12
18
i
21
Sep. 28
Sep. 27
I
to
-o
5-
-100
0
u
3
tu
CO
S-,
<U
H-
a
e
- 50
0-
c
O
-5-
15
21
3
CT
6
Sep. 30
Figure 19. Climatic elements observed at Jichidagmo(^920m)
Signs are the same as Fig. 14.
CD
©
6
9
Sep. 29
12
f(
25-
200)
u
4-3
CO
—1
a
u
en
15(D
10-
>—i
15
16
Nov. 14
21
—i—'—'—r~
12
15
-T"
18
Nov. 15
Figure 20. Climatic elements observed at Kurthang(1300m).
Signs are the same as Fig. l4. .
12
21
Nov. 16
CONCLUDING REMARKS
The following results are obtained on the basis of data observed in
1985;
1). Around Bhutan, the seasonal change from the summer monsoon period to the post-monsoon period in 1985 occurs on October 19 just after the passage of the tropical cyclone.
2). The temperature lapse r a t e indicates obvious diurnal
variation and the diurnal difference of temperature indicates
seasonal and regional differences.
3). Local circulations in Bhutan are also expected to indicate
seasonal and regional differences.
The results, above-mentioned, are closely connected with one another. In
particular, during the monsoon period, the clarification of relationships between climatic elements is an important and interesting problem.
The survey period in 1985 is from September to November and is
also from the latter part of the summer monsoon period to the postmonsoon period. Although this period includes the latter part of the monsoon period, it does not include the main period of the summer monsoon
season. Therefore, the remaining important and interesting problems concerning the monsoon in Bhutan are as follows;
1). When does the onset of the summer monsoon season occur
in Bhutan?
2). What is the relationship between Bhutan, India and Burma
regarding the onset of the summer monsoon?
3). Do the local circulations change in accordance with the onset of the summer monsoon?
4). Do the climatic conditions change in Bhutan in accordance
with the intra-seasonal variation during the summer monsoon
season?
These problems are important not only for Bhutan but for South Asia in
general. In particular, further study is considered necessary to clarify
seasonal and regional differences in the relationship between the upper
winds and local circulations and the other climatic elements. These
studies are necessary in order to clarify the regional differences in
-276-
Vegetation and soil.
ACKNOWLEDGEMENT
I wish to express my gratitude to Prof. H. Suzuki, Department of
Geography,
University of Tokyo for his guidance and encouragement.
I
also wish to express my thanks to the members of our survey group and
the Bhutanese staff.
I
used
a
HITAC
M680-H
computer
in
the
Computer
University of Tokyo.
REFERENCES
Eguchi, T (1987). Synoptic analysis of temperature,precipitation and
moisture conditions in the Bhutan Himalayas. (In this issue.)
Inoue, J. (1976). Climate of Khumbu Himal. Seppyo, 38: 66-73.
Yasunari, T. (1976). Seasonal weather variations in Khumbu Himal.
Seppyo, 40, 26-32.
-277-
Center,
-278-
PART IV
MISCELLANEOUS
LIST OF PLANTS COLLECTED IN BHUTAN, BY K. TSUCHIDA, 1985
About 1,000 plant specimens were
collected along the survey
routes by the author. These plants were
checked to identify by the
author and others in Japan.
Only plants
identified were described in
this list. The identification of plants of Bhutan is difficult because there
are few specimens in Japan and the floristic study does not still advanced. These are provisional identification.
Some specimens were identified by specialists as follows: Saxifragaceae and Crassulaceae by Dr. H.
Ohba,
University Museum, University of Tokyo, Scrophlariaceae and
Acanthaceae by Dr. T. Yamazaki, Koishikawa Botanical Garden, and
Kobresia spp. by Dr. R.K. Rajibhandari, Department of Medicinal Plants,
His Majesty's Government of Nepal. The author wishes to thank them and
Mr. N. Shirai who helped the identification of plants.
In the list, the scientific name of plants is followed by locality
from where the plants were collected, altitude of the locality and date
of collection. The species , genera and families under Gymnospermae,
Monocotyledons and Dicotyledons are arranged in alphabetic manner. -••' •
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[GYMNOSPERMAE]
EPHEDRACEAE
Ephedra gerardiana Wall. var. sikkimensis Stapf
Jichudagmo, 4,920m (Sep.29);
near Dangjoy, 4,600m (Oct.2);
near Duersachu, 3,500m . (Oct.6)
PINACEAE
Abies densa W. Griff.ex Parker
near Tsongtsothang, 3,750m
(Sep.24-)
Picea spinulosa Henry
Wangdiphodrang, 1,180m - Nikkachu, 2,580m
Nikkachu, 2,580m
(Sep.19);
(Sep.19);
near Duersachu, 3,500m
(Oct.6)
Tsuga dumosa (D.Don) Eichler
Thimphu - Dochu-la, 2,500m
(Sep.16)
CUPRESSACEAE
Juniperus wallichiana Hook.f.S Thomas.
Umatatso, A,300m
(Sep.22)
Juniperus recurva Buch,-Ham,exD.Don
Morathang, 3,580m
(Sep.21);
near Tsongtsothang, 3,750m
(Sep. 24.);
Saga-la, 4-, 920m, (Oct.5);
(Oct.11);
Gorsuem, 3,120m
Kurbang, 3,520m
(Oct.11)
Juniperus squamata Buch.-Ham.ex D.Don
Umatatso, 4,300m (Sep.22)
[ANGIOSPERMAE]
(MONOCOTYLEDONES)
AMARYLLIDACEAE
Allium wallichii Kunth
Dochu-la, 3,120ra (Sep.17)
HYPOXIDACEAE
Hypoxis aurea Lour.
Wangdiphodrang, 1,180m - Nikkachu, 2,530m
-282-
(Sep.19)
LILIACEAE
Polygonatum curvistylum Hua
near Duersachu, 3,500m
(Oct.6)
Streptopus simplex D.Don
Kurbang, 3,520m
(Oct.11)
COMMELINACEAE
Commelina benghalensis L.
Lingmethang, 720m (Oct.17)
Commelina paludosa Blume
Lobisa, 1,380m - Wangdiphodrang, 1,180m
Bumthang - Kurichu, 2,100m
(Sep.18);
(Oct.16)
Cyanotis vaga (Lour.)J.A•& J.H. Schultes
Dochu-la 3,050m
(Sep.17)
Murdannia spirata (L.) Bruckner
Kurtang, 1,300m
(Nov.15)
CYPERACEAE
Carex nubigena D.Don
Thimphu - Dochu-la, 2,500m
3,750m
(Sep.24);
(Sep.16);
Bumthang, 2,580m
Kurichu, 2,350m (Oct.16);
near Tsongtsothang,
(Oct.14.);
Thimphu, 2,370m
Bumthang -
(Oct.26)
Kobresia duthiei C.B. Clarke
Umatatso, 4,300m
(Sep.23); Yango - Rinchenze-la, 4,700m
(Sep.
27)
GRAMINEAE
Agrostis inaequiglumis Griseb.
Morathang, 3,580m
(Sep.21);
nearTsongtsothang, 3,750m
Umatatso, 4,300m
(Sep.24);
(sep.22);
Juree, 4,280m
(Oct.10)
Agrostis myriantha Hook.f.
Dochu-la, 3,120m
(Sep.18);
(Sep.17);
Kurbang,3,520m
Lobisa, 1,380m - Nikkachu, 2,580m
(Oct.11)
Agrostis nervosa Nées ex Trin.
Lobisa, 1,380m - Nikkachu, 2,580m
2,580m - Morathang, 3,580m
(Sep.18);
(Sep.20);
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Nikkachu,
Morathang, 3,580m
(Sep.21);
near Gorsuem, 3,200m
(Oct.11);
Sengor, 3,000m
(Oct.11);
Gorsuem, 3,120m
(Oct.15)
Agrostis pilosula Trin.
Thimphu - Dochu-la, 2,900m
(Sep.21);
3,750m
(Sep.16);
Umatatso, 4,300m
(Oct.6);
Morathang, 3,580m
(Sep.22);
Duersachu, 3,500m
near Tsongtsothang,
(Oct.15);
Kurbang,
3 ,520m (Oct.11 )
Andropogon munroi C.B.Clarke
Thimphu - Dochu-la, 2,900m
(Oct.11);
(Sep.16);
near Bumthang, 3,000m
Paro, 2,200m - Taxan, 3,000m
(Nov.7);
Tongsa,
2,200m (Nov.13)
Anthoxanthum sikkimense (Maxim.) Ohwi
Lobisa, 1,380m - Nikkachu, 2,580m
3,500m
(Oct.6);
Duersachu, 3,500m
(Sep.18);
near Duersachu,
(Oct.6);
Gorsuem, 3,120m
(Oct.11)
Apluda mutica L.
Kurichu, 560m (Oct.16)
Arthraxon lancifolius (Trin.) Höchst.
Thimphu, 2,370m
(Oct.26)
Arthraxon micans (Nees) Höchst.
Bumthang - Kurichu, 720m (Oct.16)
Arthraxon sikkimensis Bor
Wangdiphodrang, 1,180m - Nikkachu, 2,580m
la, 3,380m
(sep.19);
Pele-
(Nov.14)
Arundinella hookeri Munro ex Keng
Thimphu - Dochu-la, 2,900m
Nikkachu, 2,580m
(Sep.16);
(Sep.18);
2,200m - Taxan, 3,000m
Lobisa, 1,380m -
Gorsuem, 3,120m
(Oct.11);
Paro,
(Nov.7)
Arundinella nepalensios Trin.
Lingmethang, 720m (Oct.17)
Arundo donax L.
Chimilakang, 1,200m
(Nov.15)
Bothriochloa intermedia (R.Br.) A.Camus
Bumthang - Kurichu, 720m (Oct.16);
Thimphu, 2,370m
(Oct.26);
Monger, 1,680m
Chimilakang, 1,200m
(Oct.17);
(Nov.15)
Bromus staintonii Melderis
Morathang, 3,580m
(Sep.21);
Gorsuem, 3,120m
-284-
(Oct.11);
Duersachu, 3,500m (Oct.15)
Chloris virgata Swartz
Lobisa, 1,380m - Nikkachu, 2,580m
Chrysopogon aciculatus (Retz.) Trin.
Lingmethang, 720m (Oct.17);
(Sep.18)
Bumthang - Kurichu, 720m
(Oct.16)
Cymbopogon flexuosus (Nees ex Steudel) W.Watson
Thimphu - Dochu-la, 2,400m
(Sep.16)
Cynodon dactylon (1.) Pers.
Bumthang, 2,470m
(Oct.21)
Deyeuxia pulchella (Griseb.) Hook.f.
Morathang, 3,580m
(Sep.21);
near Tsongtsothang, 3,750m
Umatatso, 4,300m
(Sep.24);
Yango, 4,840m
(Sep.27); Jichudagmo, 4,920m (Sep.29);
(Oct.10); Gorsuem, 3,120m
(Oct.11);
(Oct.11);
Duersachu, 3,500m
(Sep.22);
Juree, 4,280m
near Bumthang, 3,000m
(Oct.15)
Deyeuxia scabrescens (Griseb.) Munro ex Duthie
near Duersachu, 3,500m
(Oct.6);
Kurbang, 3,520m
(Oct.11)
Digitaria cruciata (Nees ex Steudel) A.Camu.s
Dochu-la, 3,050m
2 , 580m (Sep.18);
(Sep.17);
Lobisa, 1,380m - Nikkachu,
Bumthang - Kurichu, 1,970m
Bumthang - Kurichu, 2,350m
(Oct.16);
(Oct.16)
Digitaria setigera Roth apud Roemer & Schultes
Bumthang, 2,580m
(Oct.14);
Wamay, 1,030m (Nov.12)
Digitaria stricta Roth ex Roemer&Schultes
Bumthang - Kurichu, 720m (Oct.16);
Thimphu, 2,370m
(Oct.26)
Digitaria violascens Link
Lobisa, 1,380m - Nikkachu, 2,580m
(Oct.15);
(Sep.18);
Sengor, 3,000m
Shemgang, 1,820m (Nov.11)
Echinochloa colona (L.) Link
Lingmethang, 720m (Oct.17);
Kurtang, 1,300m (Nov.15)
Eleusine indica (L.)Gaerth.
Kurichu, 560m (Oct.16);
Monger, 1,680m (Oct.17);
Bumtang - Kurichu, 930m
Lingmethang, 720m
Monger, 1,680m - Sengor, 2,900m
2 ,470m(0ct.21 );
(Oct.20);
Phuntsoling, 350m (Nov.1);
(Nov.12); Kurtang, 1,300m (Nov.15);
-285-
(Oct.16);
(Oct.17);
Bumthang,
Wamay, 1,030m
Chimilakang, 1,200m
(Nov.15)
Elymus sikkimensis (Melderis) Melderis
Thimphu -.Dochu-la, 2,500m
(Oct.11);
(Sep.16);
Sengor, 3,000m
Gorsuem, 3,120m
(Oct.15)
Elytrophorus spicatus (Willd.) A.Camus
Kurtang, 1,300m
(Nov. 15);
Eragrostis nigra Nees ex Steudel
Thimphu - Dochu-la, 2,400m
(Sep.16).;
Lobisa, 1,380m -
Nikkachu, 2,580m
(Sep.18);
Gorsuem, 3,120m
Bumthang, 3,000m
(Oct.11);
Bumthang, 2,580m
Bumthang - Kurichu, 2,350m
(0ct26);
(Oct.16);
Phuntsoling, 350m (Nov.1);
(Oct.11);
near
(Oct.1-4.);
Thimphu, 2,370m
Shemgang, 1,820m
(Nov. 11 )
Eragrostis tenella (L.) Beauvios ex Roemer & Schultes
Kurichu, 56Om (Oct.16)
Eragrostis unioloides (Retz) Nees ex Steudel
Phuntsoling, 350m (Nov.1)
Erianthus rufipilus (Steudel) Griseb.
Thimphu - Dochu-la, 2,4.00m (Sep.16);
Dochu-la, 2,600m
(Nov.16)
Festuca ovina L.
near Dangjoy, 4,600m
(Oct.2)
Festuca undata Stapf
Gorsuem, 3,120m
(Oct.11)
Gryceria tonglensis C.B. Clarke
Morathang, 3,580m
(Sep.24);
(Sep.21);
Juree, 4,280m
Helictotrichon parviflorum
(Oct.10);
near Duersachu, 3,500m
Tongsa, 2,200m
(Sep.16);
(Sep.18);
near Bumthang, 3,000m
Kurbang, 3,520m
(Oct.11)
(Hook.f.) Bor
Thimphu - Dochu-la, 2,900m
Nikkachu, 2,580m
near Tsongtsothang, 3,750m
Lobisa, 1,380m -
Morathang, 3,580m
(Sep.21);
(Oct.6);
Gorsuem, 3,120m
(Oct.11);
(Oct.11);
Thimphu, 2,370m
(Nov.4);
(Nov.13)
Heteropogon contortus (L.) Beauvois ex Roemer & Schultes
Lingmethang, 720ra (Oct.17);
Chimilakang, 1,200m
Ischaemum rugosum Salisb
Kurtang, 1,300m
(Nov.15)
-286-
(Nov.15);
Miscanthus nepalensis (Trin.) Hackel
Lobisa, 1,380m - Nikkachu, 2,580m
Kurichu, 1,970m (Oct.16);
(Oct.16);
(Sep.18);
Bumthang -
Bumthang - Kurichu, 2,100m
Dochu-la , 2,900m
(Nov.16)
Miscanthus nudipes (Griseb) Hackel
Gorsuem, 3,120m
(Oct.11);
near Bumthang, 3,000m
Thimphu, 2,370m (Oct.26);
Thimphu, 2,370m
(Oct.11);
(Nov./;)
Oplismenus burmannii (Retz.) Beauvois
Kurichu, 560m (Oct.16);
Bumthang - Kurichu, 720m
(oct.16);
Oprismenus compositus (L.) Beauvois
Wamay, 1,030m (Nov.12)
Panicum trypheron Schultes
Bumthang - Kurichu, 720m (Oct.16)
Paspalidium flavidum (Retz.) A.Camus
Bumthang - Kurichu, 930m (Oct.16);
Lingmethang, 720m
(Oct.17)
Paspalum scrobiculatum L.
Bumthang - Kurichu, 720m (Oct.16);
(Oct.17);
Lingmethang, 720m
Monger, 1,680m - Senger, 2,900m. (Oct.20);
Phuntsoling, 350m (Nov.1)
Polypogon fugax Nees ex Steudel
Phuntsoling - Thimphu, 2,150m
(Nov.1)
Saccharum spontaneum L.
Lobisa, 1,380m - Nikkachu, 2,580m
(Sep.18);
Kurthang,
1 ,300m (Nov. 15)
Sacciolepis indica (L.) Chase
Bumthang - Kurichu, 720m (Oct.16);
2,900m
Monger, 1,680m - Senger,
(Oct.20)
Setaria glauca (L.)Beauvois
Thimphu - Dochu-la, 2,400m
(Sep.16)
Sporobolus diander (Retz.) Beauvois
Monger, 1,680m (Oct.17);
Phuntsoling, 350m (Nov.1);
Bumthang - Kurichu, 720m
(Oct.16);
Chimilakang, 1,200m (Nov.15)
Sporobolus fertilis (Steudel) W.D.Clayton
Thimphu - Dochu-la, 2,400m
Nikkachu, 2,580m
(Sep.18);
(Sep.16);
Lobisa, 1,380m -
Monger, 1,680m, (Oct.17);
Phuntsoling - Thimphu, 2,150m (Nov.1);
-287-
Shemgang, 1,820m
(Nov.11);
Wamay, 1,030m
(Nov.12);
Chimilakang, 1,200m
(Nov.15)
Tripogon trifidus Munro ex Stapf
Bumthang, 2,580m (Oct.14); Paro, 2,200m - Taxan, 3,000m
(Nov.7);
Thimphu, 2,370m
(Nov.8)
Trisetum spicatum (L.) K. Richter
Morathang, 3,580m
Dangjoy, 4,600m
(Sep.21);
(Oct.2);
Yango, 4,840m
Juree, 4,200m
(Sep.27);
near
(Oct.10)
(DICOTYLEDONES)
RANUNCULACESE
Clematis napalensis DC.
Umatatso, 4,300m
(Sep.22)
Delphinium caeruleum Jacquem. ex Cambess.
Umatatso, 4,300m
(Sep.22);
Saga-la, 4,920m
(Oct.5)
Delphinium nepalense Kitam.& Tamura
Morathang, 3,580m
(Sep.21)
Delphinium stapeliosum Bruhl ex Huth
Wangdiphodrang, 1,180m - Nikkachu, 2,580m
Lobisa, 1,380m - Nikkachu, 2,580m
(Sep.19);
(Sep.19)
Ranunculus brotherusii Freyn
Jichudagmo, 4,920m
(Sep.29);
near Dangjoy, 4,600m
(Oct.2)
Ranunculus laetus Wall, ex D.Don
Shemgang, 1,820m
(Nov.11)
Thalictrum chelidonii DC.
Dochu-la, 3,120m
(Sep.17)
Thalictrum rostellatum Hook.f.S Thorns
Dochu-la, 3,050m
(Sep.17)
BERBERIDACEAE
Berberis umbellata Wall.
Morathang, 3,580m
(Sep.21);
Donshingang, 3,480m
(Oct.6);
(Oct.6); Juree, 4,280m
Sheltang, 3,450m
Umatatso, 4,300m
(Sep.22);
near Duersachu, 3,500m
(Oct.10);
(Oct.15)
-288-
Kurbang, 3,520m
(Oct.11);
PAPAVERACEARE
Corydalis longipes DC.
Dochu-la, 3,050m
(Sep.17);
Morathang, 3,580m
(Sep.21)
CRUCIFERAE
Barbarea intermedia Boreau
Morathang, 3,580m
(Sep.21)
Capsella bursa-pastoris (L.) Medikus
Bumthang, 2,580m
(Oct.K)
Thlaspi arvense L.
Bumthang, 2,580m
(Oct.K)
VIOLACEAE
Viola biflora L.
Dochu-la, 3,120m
(Sep.17)
POLYGALACEAE
Polygala linariifolia Willd
Kurtang, 1,300m
(Nov.15)
CARYOPHYLLACEAE
Arenaria glanduligera Edgew. ex Edgew.& Hook.f.
Morathang, 3,580m
Thimphu, 2,730m
(Sep.21);
Umatatso, 4,300m
(Sep.22);
(Oct.26)
Arenaria orbiculata Royle ex Edgew.& Hook.f.
Saga-la, 4,920m
(Oct.5)
Cerastium glomeratum Thuill.
Morathang, 3,580m
(Sep.21)
Sagina japonica (Swartz) Ohwi
Thimphu, 2,370m
(Oct.26);
Chimilaking, 1,200m
(Nov.15)
Silene gonosperma (Rupr.) Bocquet
near Dangjoy, 4,600m
(Oct.2)
Stellaria media (L.) Vill.
below Juree-la, 3,900m
1,200m
(Nov.1);
(Oct.10);
Shemgang, 1,820m
Phuntsoling - Thimphu,
(Nov.11);
(Nov.12)
Stellaria sikkimensis Hook.f. ex Edgew.6 Hook.f.
-289-
Wamay, 1,030m
Morathang, 3,580m
(Sep.21);
near Gorsuem, 3,200m
(Oct.11)
Stellaria vestita Kurz
Dochu-la, 3,120m
(Sep.17);
Morathang, 3,580m
Bumthang, 2,580m
(Oct. 14-);
Thimphu, 2,370m
Thimphu, 2,370m
(Sep.21);
(Oct.26);
(Nov.4)
TAMARICACEAE
Myricaria rosea W.W.Sm.
Morathang, 3,580m
(Sep.21)
HYPERICACEAE
Hypericum elodeoides Choisy
Dochu-la, 3,050m
(Sep.17);
Dochu-la, 3,120m
diphodrang, 1,180m - Nikkachu, 2,580m
2,580m
(Sep.19);
Tongsa, 2,200m
(Sep.17); Wang-
(Sep.19);
Nikkachu,
(Nov.13)
MALVACEAE
Urena lobata L.
Lingmethang, 720m (Oct.17)
TILIACEAE
Triumfetta rhomboides Jacq.
Lingmethang, 720m (Oct.17)
GERANIACEAE
Geranium donianum Sweet
Morathang, 3,580m
(Sep.21);
near Duersachu, 3,500m
(Oct.6)
Geranium lambertii Sweet
Morathang, 3,580m
(Sep.21)
Geranium nepalense Sweet
Dochu-la, 3,120m
(Sep.17);
Lobisa, 1,380m - Wangdi-
phodrang, 1,180m
(Sep.18);
Nikkachu, 2,580m
(Sep.19);
Bumthang, 2,580m
(Oct.14);
Shemgang, 1,820m
(Nov.11)
Geranium procurrens
P.F.Yeo
Thimphu, 2,370m - Dochu-la, 3,120m
3,050m
(Sep.17);
(Sep.16); Dochu-la,
Wangdiphodrang, 1,180m -Nikkachu, 2,580m
(Sep.19)
-290-
OXALIDACEAE
Oxalis corniculata L.
Chimilakang, 1,200m (Nov.15)
RUTACEAE
Boenninghausenia albiflora (Hook.) Reichenb. ex Meissn.
Thimphu, 2,370m
(Nov.8)
ACERACEAE
Acer pectinatum Wall, ex Pax
Saga-la, 4,920m (Oct.5);
Donshigang, 3,4.80m
(Oct.6)
LEGÜMINOSAE
Acacia pennata (L.) Willd.
Bumthang - Kurichu, 2,4-OOm (Sep.16);
Lingmethang, 720m
(Oct.17)
Astragalus donianus DC.
Morathang, 3,580m
(Sep.21)
Astragalus emodi Steud.
Duersachu, 3,500m
(Oct.15)
Cassia mimosoides L.
Thimphu - Dochu-la, 2,4.00m (Sep.16);
(Oct.25);
Thimphu, 2,370m
Thimphu, 2,370m
(Nov. 4.)
Cassia occidentalis L.
Kurichu, 560m (Oct.16)
Cassia tara L.
Kurthang, 1,300m (Nov.15)
Crotalaria cytisoides Roxb. ex DC.
Shemgang, 1,820m (Nov.11)
Desmodium heterocarpon (L.) DC.
Phuntsoling, 350m (Nov.1)
Desmodium microphyllum
Tongsa, 2,200m
(Thunb.) DC.
(Nov.13)
Desmodium multiflorum DC.
Thimphu - Dochu-la, 2,400m
(Oct.17);
Tongsa, 2,200m
(Sep.16);
(Nov.13)
-291-
Mongar, 1,680m
Lespedeza gerardiana Grah.
Thimphu - Dochu-la, 2,4.00m
Lespedeza cuneata
(Sep.16)
(Dum.-Cours.)G.Don
Tongsa, 2,200m
(Nov.13);
Chimilakang, 1,200m
Kurthang, 1,300m
(Nov.15);
(Nov.15)
Parochetus communis Buch.-Ham. ex D.Don
Dochu-la, 3,120m
(Sep.17);
Morathang, 3,580m
(Sep.21)
Piptanthus nepalensis (Hook.) D.Don
Sengor, 2,900m
(Oct.20)
Smithia ciliata Royle
Thimphu, 2,370m
(Oct.26)
Vicia angustifolia L.
Thimphu, 2,370m
(Oct.26)
Vigna umbellata (Thunb.) Owhi & Ohashi
Thimphu, 2,370m
(Oct.25)
Zornia gibbosa Spanoghe
Lobisa, 1,380m - Nikkachu, 2,580m
(Sep.18);
Chimilakang,
1 ,200m (Nov.15)
ROSACEAE
Agrimonia pilosa Ledeb. var. nepalensis (D.Don) Nakai
Thimphu - Dochu-la, 2,900m
diphodrang, 1,180m
(Sep.16); Lobisa, 1,380m - Wang-
(Sep.18)
Duchesnea indica (Andr.) Focke
Dochu-la, 3,050m
(Sep.17)
Potentilla ambigua Cambess.
Morathang, 3,580m
(Sep.21)
Potentilla fructicosa L.
Jichudagmo, U,920m (Sep.29)
Potentilla fulgens Wall, ex Hook.
Thimphu,2,370m - Dochu-la, 3,120m
(Sep.16); Dochu-la, 3,120m
(Sep.17)
Potentilla griffithii Hook. f.
Thimphu - Dochu-la, 2,900m
(Sep.17);
(Sep.16);
Dochu-la, 3,050m
Wamngdiphodrang, 1,180m - Nikkachu, 2,580m
(Sep.19); Bumthang, 2,580m
Potentilla microphylla D. Don
Umatatso, 4,300m
(Oct.14-)
(Sep.22)
-292-
Potentilla saundersiana Royle
near Dangjoy, 4,600m
(Oct.2)
Prunus rufa Hook. f.
near Tsongtsothang, 3,750m
(Sep.24)
Rosa sericea Lindl.
Lobisa, 1,380m - Wangdiphodrang, 1,180m
Nikkachu, 2,580m
(Sep.18);
(Sep.19);
Donshigang, 3,480m
Dochu-la, 2,120m
(Sep.17);
Monger, 1,680m
Shemgang, 1,820m
(Nov.11)
(Oct.6)
Rubus ellipticus Smith
(Oct.17);
Rubus pedunculosus auct non D.Don
Donshingang, 3,480m
(Oct.6)
Sanguisorba diandra (Hook.f.) Nordborg
Duersachu, 3,500m
(Oct.15)
Sorbus microphylla Wenzig
Umatatso, 4,300m
(Sep.22)
Spiraea arcuata Hook.f.
Umatatso, 4,300m
(Sep.22)
Spiraea micrantha Hook.f.
Duersachu, 3,500m
(Oct.15)
SAXIFRAGACEAE
Chrysosplenium forrestii Diels
Umatatso, 4,300m
(Sep.22)
Saxifraga montanella H.Smith
Morathang, 3,580m
(Sep.21);
Umatatso, 4,300m
Saxifraga moorcroftiana (Seringe) Wall, ex Sternb.
Morathang, 3,580m
(Sep'.21)
Saxifraga sphaeradena H.Smith
Morathang, 3,580m
(Sep.21)
HYDRANGEACEAE
Hydrangea aspera Buch. - Ham. ex D.Don
Donshigang, 3,480m
(Oct.6)
CRASSULACEAE
Rhodiola crenulata (Hook.f.S Thorns.) H.Ohba
-293-
(Sep.22)
Yango, 4,840m (Sep.27)
Rhodiola wallichiana (Hook.) Fu
Saga-la, 4-,920m (Oct.5)
DROSERACEAE
Drosera peltata Smith
near Duersachu, 3,500m
(Oct.15)
CALLITRICHACEAE
Calltriche stagnalis Scopoli
Sengor, 3,000m
(Oct.15)
MELASTOMATACEAE
Osbeckia sikkimensis Craib
Thimphu, 2,370m
(Nov.4);
Shemgang, 1,820m (Nov.11)
ONAGRACEAE
Epilobium wallichianum Hausskn.
Dochu-la, 3,120m
(Sep.17);
Donshigang, 3,480m
Morathang, 3,580m
(Oct.6)
UMBELLIFERAE
Bupleurum candollii Wall, ex
near Duersachu, 3,500m
DC.
(Oct.6)
Cortia depressa (D.Don) C.Norman
Umatatso, 4,300m (Sep.22)
Cortiella hookeri (C.B.Clarke) C.Norman
Saga-la,4,920m
(Oct.5)
Selinum candollii DC.
near Duersachu, 3,500m
(Oct.6)
CAPRIFOLIACEAE
Leycesteria gracilis (Kurz) Airy Shaw
Bumthang - Kurichu, 2,000m
(Oct.16)
Lonicera myrtillus Hook.f.6 Thorns.
near Dangjoy, 4,600m (Oct.2)
-294-
(Sep.21);
SAMBUCACEAE
Sambucus adnata Wall.
Dochu-la, 3,120m
(Sep.17)
Viburnum coriaceum Blume
Tongsa, 2,200m
(Nov.13)
RUBIACEAE
Borreria alata (Aubl.) DC.
Phuntsoling, 350m (Nov.1 )
Coffea benghalensis Heyne ex Roem.6 Schult..
Phuntsoling, 350m - Thimphu, 2,370m
(Nov.2)
Galium asperifolium Wall.
Dochu-la, 3,050m
(Sep.17);
Lobisa, 1,380m - Wangdi-
phodrang, 1,180m
(Sep.18);
Donshigang, 3,480m
near Gorsuem, 3,200m
Tongsa, 2,200m
(Oct.11);
Gorsuem, 3,120m
(Oct.6);
(Oct.11);
(Nov.13)
Leptodermis kumaonensis Parker
Thimphu, 2,370m
(Oct.26)
Rubia wallichiana Décrie.
Monger, 1,680m
(Oct.17)
DIPSACACEAE
Dipsacus inermis wall.var.mitis (D.Don) Y.Nasir
Dochu-la, 3,120m
(Sep.17)
COMPOSITAE
Adenostemma lavenia (L.) Kuntze
Bumthang - Kurichu, 2,000m
(Oct.16)
Ageratum conyzoides L.
Lingmethang, 720m (Oct.17);
Kurichu, 56Om (Oct.16)
Ainsliaea aptera DC.
Dochu-la, 3,050m
(Sep.17)
Anaphalis busua (Buch.-Ham. ex D.Don) DC.
Thimphu - Dochu-la, 2,4.00m (Sep.16);
Dochu-la, 3,120m
(Sep.16);
Thimphu, 2,370m -
Dochu-la, 3,050m
(Sep.17)
Anaphalis margaritacea (L.) Benth.
Thimphu - Dochu-la,2,900m
(Sep.16); Lobisa, 1,380m - Wang-
295-
diphodrang, 1,180m
Shemgang, 1,820m
(Sep.18);
Duersachu, 3,500m
(Oct.15);
(Nov.11)
Anapharis triplinervis (Sims) C.B.Clarke
Lobisa, 1,380m - Wang di Phodrang, 1,180m
Lobisa, 1,380m - Nikkachu, 2,580m
(Sep.18);
(Sep.18);
2,580m
(Sep.19);
Morathang, 3,580m
4,300m
(Sep.22);
Saga-la, A,920m
(Sep.21);
Nikkachu,
Umatatso,
(Oct.5)
Artemisia dubia Wall, ex Besser
Thimphu - Dochu-la, 2,400m
(Sep.16);
Dochu-la, 3,050m,
(Sep.17)
Artemisia indica Willd.
Thimphu - Dochu-la, 2,4-OOm (Sep.16);
Dochula, 3,120m,
(Sep.17);
Lobisa, 1,380m - Wangdiphodrang, 1,180m,
(Sep.18);
Duersachu, 3,500m
(Oct.11);
Bumthang - Kurichu, 720m (Oct.16);
1,200m
(Oct.15);
Gorsuem, 3,120m
Chimilakang,
(Nov.15)
Bidens pilosa L.
Lingmethang, 720m (Oct.17);
(Oct.16);
Shemgang, 1,820m
Bumthang - Kurichu, 2,000m
(Nov.11)
Bidens tripartita L.
Thimphu, 2,370m
(Oct.26)
Cacalia pentaloba Hand. Mazz
Kurbang, 3,520m
(Oct.11)
Carpesium nepalense Less.
Dochu-la, 3,120m
(Sep.17)
Cicerbita macrorhiza (Royle) Beauv.
Morathang, 3,580m
(Sep.21)
Cirsium falconeri (Hook.f.) Petrak
Morathang, 3,580m
(Sep.21)
Crisium tribeticum Kitam.
Nikkachu, 2,580m
(Sep.19)
Crisium verutum (D.Don) Spreng.
Dochu-la, 3,120m
(Sep.17);
Bumthang - Kurichu, 2,350m,
(Oct.16)
Conyza stricta Willd.
Thimphu - Dochu-la, 2,4-OOm (Sep.16);
(Oct.26);
Thimphu, 2,370m
(Nov.4)
-296-
Thimphu, 2,370m
Dubyaea hispida DC.
Dochu-la, 3,120m
(Sep.17);
Gorsuem, 3,120m
(Oct.11)
Elephantopus scaber L.
Phuntsoling, 350m (Nov.1)
Emilia sonchifolia (L.) DC.
Chimilakang, 1,200m
(Nov.15)
Erigeron bellidioides (Buch. - Ham. ex D.Don) Benth. ex C.B.
Clarke
Thimphu, 2,370m - Dochu-la, 3,120m
- Nikkachu, 2,580m
Nikkachu, 2,580m
(Sep.18);
(Sep.19);
(Sep.16);
Lobisa, 1,380m
Wangdiphodrang, 1,180m Morathang, 3,580m
(Sep.21)
Eupatorium adenophorum Spreng.
Lobisa, 1,380m - Nikkachu, 2,580m
350m - Thimphu, 2,370m
(Sep.18);
Phuntsoling,
(Nov.1)
Eupatorium odoratum L.
Lingmethang, 720m (Oct.17)
Galinsoga parviflora Cav.
Lobisa, 1,380m - Wangdiphodrang, 1,180m
Bumthang, 2,580m
Thimphu, 2,370m
(Oct.K);
(Sep.18);
Lingmethang, 720m
(Oct.17);
(Oct.26)
Gnaphalium affine D.Don
Thimphu, 2,370m
(Oct.26);
Shemgang, 1,820m
(Nov. 11)
Gnaphalium hypoleucum DC.
Thimphu, - Dochu-la, (Sep.16);
Umatatso, 4,300m
(Sep.22)
Inula cappa (Buch.-Ham. ex D.Don) DC.
Sheltang, 3,450m
(Oct.15);
Lingmethang, 720m
(Oct.17)
Inula hookeri C.B. Clarke.
Nikkachu, 2,580m - Morathang, 3,580m
(Sep.20)
Leibnitzia nepalensis (Kunze) Kitam.
near Duersachu, 3,500m
(Oct.6)
Myriactis nepalensis Less.
Thimphu - Dochu-la, 2,900m
1,180m - Nikkachu, 2,580m
(Sep.16);
(Sep.19);
(Sep.17)
Saussurea auriculata (DC.) Sch.
Dochu-la, 3,050m
(Sep.17)
Saussurea gossypiphora D.Don
-297-
Wangdiphodrang,
Dochu-la , 3,120m
Morathang, 3,580m (Sep.21)
Saussurea obvallata (DC.) Edgew.
Duersachu, 3,500m (Oct.15)
Saussurea pachyneura Franch.
Umatatso, 4.,300m (Sep.22)
Saussurea tridactyla Sch. Bip. ex Hook, f.
Morathang, 3,580m (Sep.21)
Senecio chrysanthemoides DC.
Thimphu, 2,370m - Dochu-la, 3,120m (Sep.16); Dochu-la,
3,050m
Siegesbeckia orientalis L.
Thimphu - Dochu-la, 2,4.00m (Sep.16); Bumthang, 2,580m
(Oct. H )
Spilanthes iabadicensis A.H.Moore
Shemgang, 1,820m (Nov.11); Wamay, 1,030m (Nov.12)
Synedrella nodiflora Gaertn.
Phuntsoling, 350m (Nov.1)
Tanacetum gossypinum Hook.f.6Thoms . ex C.B.CLarke
Yango, 4,840m (Sep.27)
Tridax procumbens L.
Lingmethang, 720m (Oct.17); Phuntsoling, 350m (Nov.1)
CAMPANURACEAE
Campanula pallida Wall.
Thimphu, - Dochu-la, 2,900m (Sep.16); Lobisa, 1,380m Nikkachu, 2,580m (Sep.18); Morathang, 3,580m (Sep.21);
Tongsa, 2,200m (Nov.13)
Cyananthus inflaus Hook.f.&Thoms.
Dochu-la, 3,050m (Sep.17); Dochu-la, 3,120m, (Sep.17)
Cyananthus lobatu Wall, ex Benth.
near Kurbang, 3,850m (Oct.11)
Lobelia erectiuscula Hara
Dochu-la, 3,120m (Sep.17)
Lobelia pyramidalis Wall.
Bumthang - Kurichu, 1,800m(oct.16)
ERICACEAE
-298-
Cassiope fastigiata
(Wall.)D.Don
Umatatso, 4,300m
(Sep.22);
Yango, 4,84.0m
(Sep.27)
Wangdiphodrang, 1,180m - Nikkachu, 2,580m
(Sep.19)
Gaultheria nummularioides D.Don
Gaultheria trichophylla Royle
Morathang, 3,580m
(Sep.21)
Rhododendron anthopogon D.Don
Yango, 4,840m
(Sep.27)
Rhododendron campanulatum D.Don vrar. wallichii Hook. f.
Umatatso, 4,300m
(Sep.22);
Juree, 4,280m
(Oct.10)
Rhododendron lepidotum Wall, ex G.Don
near Duersachu, 3,500m
Duersachu, 3,500m
(Oct.6);
Gorsuem, 3,120m
(Oct.11);
(Oct.15)
Rhododendron nivale Hook.f.
Yango, 4,840m
(Sep.27);
Jichudagmo, 4,920m
(Sep.29)
Rhododendron setosum D.Don
Umatatso, 4,300m
(Sep.22)
Rhododendron thomsonii Hook.f.
Nikkachu, 2,580m - Morathang, 3,580m
(Sep.20)
PRIMULACEAE
Primula capitata Hook.f.
Thimphu, 2,370m - Dochu-la, 3,120m
(Sep.16)
Primula primulina (Spreng.) Hara
Umatatso, 4,300m
(Sep.22)
MYRSINACEAE
Maesa rugosa C.B.Clarke
Bumthang - Kurichu, 2,100m
(Oct.16)
GENTIACEAE
Gentiana algida Pall.
Umatatso, 4,300m
(Sep.22);
near Dangjoy, 4,600m
Gentiana lacerulata H. Sm.
Umatatso, 4,300m
(Sep.22)
Halenia ellipitica D.Don
Thimphu - Dochu-la, 2,900m
(Sep.16)
-299-
(Oct.2)
Lomatogonium micranthum
Tongsa, 2,200m
H.Sm.
(Nov.13)
Swertia kingii Hook.f.
Morathang, 3,580m
(Sep.21)
Swertia nervosa (G.Don) C.B. Clarke
Thimphu - Dochu-la, 2,4.00m
(Sep.16)
SCROPHULARIACEAE
Euphrasia schlagintweitii Wettst.
Wangdiphodrang, 1,180m - Nikkachu, 2,580m
Morathang, 3-,58Om (Sep.21);
(Sep.19);
Tongsa, 2,200m
(Nov.13)
Hemiphragma heterophyllum Wall.
Thimphu - Dochu-la, 2,900m
(Sep.17);
(Sep.16);
Dochu-la, 3,120m
1180m - Nikkachu, 2,580m
Dochu-la, 3,O5Om
(Sep.17);
(Sep.19);
Wangdiphodrang,
Gorsuem, 3,120m
Mazus deravayi Bonati
Thimphu - Dochu-la, 2,500m
(Sep.16)
Pedicularis longiflora Rudolph
Morathang, 3,580m
(Sep.21)
Pedicularis megalantha D.Don
Dochu-la, 3,120m
(Sep.17)
Pedicularis pennelliana Tsoong
Nikkachu, 2,580m - Morathang, 3,580m
Pedicularis siphonantha D.Don
Umatatso, 4,300m
(Sep.22)
Veronica umbelliformis Pennell
Umatatso, 4.,3OOm
(Sep.22)
ACANTHACEAE
Barleria cristata L.
Lingmethang, 720m
(Oct.17)
Dicliptera bupleuroides Nees
Phuntsoling, 35Om (Nov.1)
Rungia parviflora (Retz.) Nees
Phuntsoling, 35Om
(Nov.1)
VERBENACEAE
-300-
(Sep.20)
(Oct.11)
Verbena officinalis L.
Monger, 1,680m
(Oct.17);
Thimphu, 2,370m
(Oct.25)
LABIATAE
Clinopodium urabrosum (M.Bieb.) C.Koch
Lobisa, 1,380m - Wangdiphodrang, 1,180m
(Sep.18);
la, 3,120m
(Sep.21)
(Sep.17);
Morathang, 3,580m
Dochu-
Elsholtzia strobilifera (Benth.) Benth.
Morathang, 3,580m
(Sep.21)
Eriophyton wallichii Benth.
Yango, 4,840m
(Sep.27)
Lamium amplexicaule L.
Wamay, 1,030m
(Nov.12)
Leucas cephalotes (Roth) Spreng.
Lingmethang, 720m
(Oct.17)
Nepeta lamiopsis Benth. ex Hook.f.
Morathang, 3,580m
(Sep.21)
Origanum vulgäre L.
Lobisa, 1,380m - Nikkachu, 2,580m
rang, 1,180m - Nikkachu, 2,580m
(Sep.18);
(Sep.19);
WangdiphodTongsa, 2,200m
(Nov.13)
Prunella vulgaris L.
Thimphu, 2,370m - Dochu-la, 3,120m
3,050m
(Sep.17);
Morathang, 3,580m
(Sep.i6);
(Sep.21);
Dochu-la,
Donshigang,
3,4-8Om (Oct.6)
Rabdosia coesta (Buch.-Ham. ex D.Don) Hara
Bumthang - Kurichu, 1,900m (Oct.16)
.<••-•-•--.
Salvia campanulata Wall, ex Benth.
Dochu-la, 3,120
(Sep.17)
PLANTAGINACEAE
Plantago erosa Wall.
Dochu-la, 3,050m
(Sep.17);
Morathang, 3,580m
AMARANTHACEAE
Achyranthes bidentata Blume
Shemgang, 1,820m
(Nov.11)
-301-
(Sep.21)
Alternanthera sessilis (L.) DC.
Lingmethang, 720m (Oct.17)
Amaranthus caudatus L.
Thimphu - Dochu-la, 2,500m
(Sep.16);
Thimphu, 2,370m
(Oct.26)
Amaranthus viridis L.
Monger, 1,680m
(Oct.17);
Thimphu, 2,370m
Lingmethang, 720m
(Oct.26);
Wamay, 1,030m
(Oct.17);
(Nov.12)
Cyathula prostrata (L.) Blume
Phuntsoling, 350m (Nov.1)
CHENOPODIACEAE
Chenopodium album L.
Bumthang, 2,580m
(Oct.14);
Lingmethang, 720m (Oct.17)
POLYGONACEAE
Aconogonum molle (D.Don) Hara
Dochu-la,. 3,120m
(Sep.17);
near Gorsuem, 3,200m
Shemgang, 1,820m
Morathang, 3,580m
(Oct.11);
Gorsuem, 3,120m
(Sep.21);
(Oct.11);
(Nov.11)
Bistorta macrophylla (D.Don) Sojak
near Rinchenze-la, 4,800m
(Sep.27)
Bistorta vaccifolia (Wall, ex Meisn.) Greene
ümatatso, 4,300m
(Sep.22)
Bistorta vivipara (L.) Spach
Ümatatso, 4,300m
Persicaria hydropiper
Bumthang, 2,580m
(Sep.22)
(L.)Spach
(Oct.14)
Persicaria nepalensis (Meisn.) H.Gross
Thimphu - Dochu-la, 2,500m
(Sep.19);
(Sep.16);
Morathang, 3,580m
Nikkachu, 2,580m
(Sep.21)
Persicaria pubescens (Blume) Hara var. acuminata (Franch.S Sav.)
Hara
Bumthang - Kurichu, 1,800m
(Oct.16)
Persicaria runcinata (Buch.-Ham. ex D.Don) H.Gross
Dochu-la, 3,120m
(Sep.24);
(Sep.17);
near Tsongsothang, 3,750m
Bumthang, 2,580m
(Oct.14);
-302-
Monger, 1,680m
(Oct.17)
Persicaria tenella (Blume) Hara
Kurthang, 1,300m (Nov.15)
Rumex nepalensis Spreng.
Dochu-la 3,120m
(Sep.17)
ELAEAGNACEAE
Elaeagnus parvifolia Wall, ex Royle
Nikkachu, 2,580m
Thimphu, 2,370m
(Sep.19);
Thimphu, 2,370m
(Nov.8)
EUPHORBIACEAE
Euphorbia hirta L.
Kurichu, 56Om (Oct.16)
Phyllanthus virgatus G.Forst.
Lingmethang, 720m (Oct.17)
URTICACEAE
Debregeasia longifolia (Burm.f.) Wedd.
Bumthang - Kurichu, 1,800m (Oct.16)
BETULACEAE
Betula utilis D.Don
near Gorsuem, 3,200m
(Oct.11)
-303-
(Nov
-304-
ITINERARY
Date:
Region:
Route:
September-November 1985
Bhutan(mainly in the central part)
Narita-*-Calcutta-*-Paro=Thimphu=Wangdhu
Members:
Gophu La-Bumthang=Mongar=Lingmethang-Manas-Shemgang=
Tongsa=Nikkachu=Pele La=Wangdhu Phodrang= Punakha=
Dochu La=Thimphu=Phuntsoling-*-Calcutta-*-Narita
Masahiko Ohsawa
Chiba University
Contents:
Phodrang=Nikkachu-
Makoto Numata
Shukutoku University
Katsuyoshi Tsuchida
Masanori Okazaki
Shinshu University
Tokyo University of Agricultur
and Technology
Takashi Eguchi
University of Tokyo
Route, weather and some remarks
1). Route
Station name(altitude;time of departure,
passing and arrival).
( -*- by air,
2). Weather(W)
=
by car,
-
on foot)
F-F-C-R-S indicates the weather conditions
around 6, 9, 12, 15, 18 Bhutan Standard Time
respectively.
( F-fine, C-cloudy, R-rain, S-snow )
-305-
8 9V
8 9 30'
9 0'0'
9 2'0'
9O"3O"
Survey
route
BHUTAN
v
CHINA /
^
C'!
/
i
•*'
BANGLA
INDIA
+28'O'
P3 H ;V
ç-AJ-^
y
1
./
J
^
•
\
BURMA
f
/
0
i
o
50oK^
tO 20 30 t-0
i
i
i
I
27'3O -
+
T
SAMC11I
3 ? f PHUNTSOLING
890
Figure 1. Survey route map of Bhutan.
27' 0 -
15
I
CO
20 KM
J
2 n o'_
o
90'15'
Figure 2. Survey roqt
in the central part 2000
of Bhutan.
1
9l"00'
I
91'IS'
-808Altltude
o
o
o
o
O
O
O
O
O
O
ui
O
O
O
en
O
o
o
o
I
THIMPHU •
OP
CD
PUNAKHA _
i T
KURTHANG
LOBISA(MISHINA)k- -~"
WANGDI PHODRANG*" ~"
NIKKACHU,
;»DOCHU LA
-^
PELE LA
CD
TONGSA^
et"
: MORATHANG
O
^N-UMATATSO
SHEMGANG>'
/
DAKPHEY
c+
CD
TSONGTSOTHANG
cn
CD
o
,YANGO
O
ti
^
•J
O
ECHUDAGMO
Hj
c^!3-
DUMMONG
TSACHU
ÏOCHENA
(D
JYAZE LA
IGJOY
W
i-J
<;
CD
RINCHENZE LA
\.TSOREIM
PANGTHANG
^ > G O P H U LA
3
GECHEWOMA
I
YAK CAMP
00
SAGA LA
DONSHIGANG
DUERSACHU
JUREE
JUREE LA
KURBANG
'GORSUEM
SILAMBI
RTNDERGANG
BUMTHANG
SENGOR
THURUMSENG LA
September 1985
4: Eguchi leaving the Narita Air Port(Japan) for Calcutta.
11: Ohsawa, Numata, Tsuchida and Okazaki leaving the Narita
Air Port for Calcutta.
[Ohsawa, Numata,Tsuchida,Okazaki,Eguchi]
13: Calcutta-*-Paro(2360m)=Thimphu(2370m)
14: Thimphu
15: Thimphu
(W) Heavy rain in the late afternoon through nighttime.
16: Thimphu(2370m)=Dochu La(3120m)
(W) R-F-F-C-F. Heavy rain(nighttime).
Land slide between Dochu La and Lobisa.
17: Dochu La=Lobisa( 1380m)
(W) F-C-C-R-F. Heavy rain(14:00-15:00).
18: Lobisa=Wangdi Phodrang(1360m)=Pele La(3380m)=Nikkachu(2580m)
(W) C-F-R-C-C. Rain around Pele La.
19: Nikkachu
(W) C-F-R-C-C.
[Numata]
20: Nikkachu=Thimphu
21: Thimphu(survey around Thimphu)
22: Thimphu
23: Thimphu=Paro
24: Paro-*-Calcutta-*-Narita
25: arrived at the Narita Air Port.
[Ohsawa,Tsuchida,Okazaki,Eguchi]
20: Nikkachu(8:50)-Morathang(3580m; 19:00)
(W) F-C-R-R-R. Rain(13:00-19:00,nighttime)
21: Morathang
(W) F-F-F-R-R. Rain( 13:00-
)
Heavy Rain(17:15- )
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22: Morathang(8:15)-Umatatso(4300m; 16:00)
(W) C-C-C-C-C. Rain(7:00-8:00,13:00-17:30)
23: Umatatso(10:30)-Tampey La(4620m;12:30)-Tampeytso(4300m; 14:30)
(W) F-C-C-C-R. Rain( 16:00-19:00)
24: Tampeytso(8:30)-Tsongtsothang(4340m; 16:40)
(W) C-C-C-R-R. Rain(12:15-19:00).
25: Tsongtsothang
(W) C-C-C-R-R. Rain( 14:00- ).
26:Tsongtsothang(ll:20)-Yango(4840m; 17:00)
(W) C-R-C-R-R. Rain(8:50-10:50,14:00- ). Graupel during nighttime.
27: Yango(8:50)-Rinchenze La(5240m;15:00)-Jichudagmo(4920m; 17:00)
(W) F-F-F-F-S. Snow( 17:20- ).
28: Jichudagmo
(W) C-C-S-F-F. Snow( 12:00-13:00).
29: Jichudagmo
(W) F-F-C-S-C. Snow( 13:30-17:00).
30: Jichudagmo(8:15)-Tsochena(4880m; 13:50)
(W) F-F-C-C-S. Snow(17:30-).
October 1985
1: Tsochena(8:30)-Jyaze La(5100m;10:45)Dangjoy(4650m; 13:00)
(W) F-F-C-S-S. Snow( 14:00- ).
2: Dangjoy(9:35)-Tsoreim(5200m; 15:00)
(W) F-F-F-F-F. No rain and snow.
3: Tsoreim(8:45)-Gophu La(5300m;10:30)-Gechewoma(4600m;17:15)
(W) F-F-F-F-F. No rain and snow.
4: Gechewoma(8:30)-Yak Camp(4660m; 15:30)
(W) F-F-F-F-C. Rain( 18:30- ).
5: Yak Camp(8:45)-Saga La(4920m;10:20)-Donshigang(3480m;17:15)
(W) F-F-F-C-C. Graupel around 14:00.
Rain around 17:00.
6: Donshigang(10:00)-Duersachu(3400m; 12:00)
(W) F-F-F-C-C. Rain during nighttime.
7: Duersachu
(W) C-C-C-C-C. Rain in the rarly morning.
8: Duersachu
(W) C-C-C-R-R.
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9: Duersachu(9:30)-Juree(4280m;16:15)
(W) C-R-R-R-R.
10: Juree(9:30)-Juree La(4700m;l l:45)-Kurbang(3520m; 17:30)
(W) R-C-C-R-C. Heavy rain(12:50-15:00).
11 : Kurbang( 12:20)-Gorsuem(3120m; 15:00)
(W) F-C-C-F-F. No rain.
12: Gorsuem(8:00)-Bumthang(2580m; 17:40)
(W) C-C-C-F-F. Rain around 12:00.
13: Bumthang
(W) F-F-F-F-F. No rain.
14: Bumthang
(W) F-F-F-F-F. No rain.
15: Bumthang=ThurumsengLa(3780m)=Sengor(3000m)
(W) F-F-F-C-C. Heavy rain during nighttime.
16: Sengor=Mongar( 1680m)
(W) R-R-R-R-R.
17: Mongar
(W) R-R-R-R-R.
18: Mongar=Lingmethang(720m)
(W) R-R-C-F-F. Rain( -11:00).
19: Lingmethang
(W) F-F-F-F-F. No rain.
[Tsuchida]
20: Lingmethang=Bumthang
21: Bumthang=Thimphu
22: Thimphu(survey around Thimphu until November 9)
(November 10): Thimphu=Tongsa
(November 11): Tongsa=Shemgang
[Ohsawa,Okazaki,Eguchi]
20: Lingmethang(7:50)-Eruthang La(1950m;16:00)-Rindergang(1300m; 17:30)
(W) F-F-F-F-F. No rain.
21: Rindergang
(W) F-C-F-F-C. No rain.
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22: Rindergang(7:00)-Shele La(2500m;l l:30)-Doh La(2400m;15:15)Silambi(1820m; 17:00)
(W) C-F-F-F-F. No rain.
23: Silambi(8:20)-Nagor( 1550m; 17:00)
(W) F-F-F-F-F. No rain.
24: Dali( 1500m; 14:30)-Umshalbi(670m; 18:00)
(W) F-F-F-F-F. No rain.
25: Umshalbi(8:15)-Dogar(1110m;ll:30)
(W) F-F-F-C-C. Rain( 15:30-17:00).
26: Dogar(7:40)-Derthang La(1300m;9:40)-Nganla(1280m;14:00)
(W) C-F-C-C-F. Rain(16:00-17:30).
27: Nganla(8:10)-Pangbang(200m; 18:00)
(W) C-C-C-F-F. No rain.
28: Pangbang
(W) F-F-F-F-F. No rain.
29: Pangbang(8:30)-Manas( 140m; 15:30)
(W) F-F-F-F-F. No rain.
30: Manas
(W) F-F-F-F-F. No rain.
31: Manas(8:15)-Pangbang( 15:00)
(W) F-F-F-F-F. No rain.
November 1985
1 : Pangbang(8:20)-Changang(210m; 16:30)
(W) F-F-F-C-C. Rain(14:00-14:30).
2: Changang(8:00)-Pangthang(240m; 17:00)
(W) F-F-F-F-F. No rain.
3: Pangthang
(W) F-F-F-F-F. No rain.
4: Pangthang(7:45)-Gomphu( 1480m; 18:00)
(W) F-F-F-C-C. No rain.
5: Gomphu(8:00)-Dummong Tsachu(320m; 12:00)
(W) C-C-F-F-C. Rain(l 1:00-1 l:30,Nighttime).
6: Dummong Tsachu(8:00)-Tshaidang( 1400m; 18:00)
(W) C-R-F-C-C. Rain(7:00-9:00).
7: Tshaidang(8:00)-Buri( 1720m; 17:00)
(W) F-F-F-C-R. Heavy rain( 16:30- ).
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8: Buri
(W) C-C-C-C-C. Rain(7:30-8:00,19:00-19:40,Nighttime)
9: Buri(7:45)-Taley(1740m;14:00)
(W) C-C-F-C-C. No rain.
10: Taley(9:00)-Dakphey( 1320m; 13:00)
(W) F-C-F-C-F. No rain.
11 : Dakphey=Shemgang( 1820m)
(W) F-F-F-F-F. No rain.
[Ohsawa,Tsuchida,Okazaki,Eguchi]
12: Shemgang=Tongsa(2200m)
(W) F-F-F-F-F. No rain.
13: Tongsa
(W) F-F-F-F-F. No rain.
14: Tongsa=Pele La=Kurthang( 1300m)
(W) F-F-F-F-F. No rain.
15: Kurthang
(W) F-F-F-F-F. No rain.
16: Kurthang=Dochu La=Thimphu
(W) F-F-F-F-F. No rain.
17: Thimphu
18: Thimphu
19: Thimphu
Thimnhn
20: Thimphu
A
4
21: Thimphu=Phuntsoling
26: Ohsawa,Tsuchida and Okazaki leaving Calcutta for Japan.
27: Ohsawa, Tsuchida and Okazaki arrived
at the Narita Air Port.
29: Eguchi leaving Calcutta for Japan.
30: Eguchi arrived at the Narita Air Port.
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