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ACTA METEOROLOGICA SINICA
VOL.21
Long-Term Trend and Abrupt Change for Major Climate Variables
in the Upper Yellow River Basin∗
ZHAO Fangfang† (
), XU Zongxue (
), and HUANG Junxiong(
)
Key Laboratory of Water and Sediment Sciences of the Ministry of Education, College of Water Sciences,
Beijing Normal University, Beijing 100875
(Received March 14, 2007)
ABSTRACT
On the basis of the mean air temperature, precipitation, sunshine duration, and pan evaporation from
23 meteorological stations in the upper Yellow River Basin from 1960 to 2001, the feasibility of using
hypothesis test techniques to detect the long-term trend for major climate variables has been investigated.
Parametric tests are limited by the assumptions such as the normality and constant variance of the error
terms. Nonparametric tests have not these additional assumptions and are better adapted to the trend test
for hydro-meteorological time series. The possible trends of annual and monthly climatic time series are
detected by using a non-parametric method and the abrupt changes have been examined in terms of 5-yr
moving averaged seasonal and annual series by using moving T-test (MTT) method, Yamamoto method,
and Mann-Kendall method. The results show that the annual mean temperature has increased by 0.8 ◦ C in
the upper Yellow River Basin during the past 42 years. The warmest center was located in the northern
part of the basin. The nonlinear tendency for annual precipitation was negative during the same period.
The declining center for annual precipitation was located in the eastern part and the center of the basin.
The variation of annual precipitation in the upper Yellow River Basin during the past 42 years exhibited
an increasing tendency from 1972 to 1989 and a decreasing tendency from 1990 to 2001. The nonlinear
tendencies for annual sunshine duration and pan evaporation were also negative. They have decreased by
125.6 h and 161.3 mm during the past 42 years, respectively. The test for abrupt changes by using MTT
method shows that an abrupt warming occurred in the late 1980s. An abrupt change of the annual mean
precipitation occurred in the middle 1980s and an abrupt change of the mean sunshine duration took place in
the early 1980s. For the annual mean pan evaporation, two abrupt changes took place in the 1980s and the
early 1990s. The test results of the Yamamoto method show that the abrupt changes mostly occurred in the
1980s, and two acute abrupt changes were tested for the spring pan evaporation in 1981 and for the annual
mean temperature in 1985. According to the Mann-Kendall method, the abrupt changes of the temperature
mainly occurred in the 1990s, the pan evaporation abrupt changes mostly occurred in the 1960s, and the
abrupt changes of the sunshine duration primarily took place in the 1980s. Although the results obtained by
using three methods are different, it is undoubted that jumps have indeed occurred in the last four decades.
Key words: climate change, trend, abrupt change, the Yellow River
1. Introduction
The working meeting, co-organized by the International Geosphere-Biosphere Program (IGBP) and
World Climate Research Program (WCRP), was held
at Venice City, Italy in November 1994. There were
six issues confirmed in the meeting, of which climate
abrupt dynamics and climate change evaluation were
two important issues (Wang, 1997). In recent years,
the regional climate change issues related with the
activities of people property have become one of the
most important issues (Yan et al., 2001). The cli-
mate system has typical characteristics of multi-scale
in space, multi-layer in configuration, nonlinearity in
nature, with complex mutual connection and effect
(Li, 2001). Many researchers investigated the trend
of climate variables and the characteristics of the climate abrupt changes. For example, the summer climate jumps in the Northern Hemisphere in summer of
the 1960s (Yan et al., 1990, 1992), the tendencies and
climate jumps of four main climate variables in
the Sanjiang Plain using accumulated departure, Jy parameter, Yamamoto method, and
Mann-Kendall method (Yan et al., 2001, 2003), the
∗ Supported by the “Jingshi scholar” Leading Professor Program, Beijing Normal University and the National Basic Research
Program (973) of China under Grant No. 1999043601.
† Corresponding author: [email protected].
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ZHAO Fangfang, XU Zongxue and HUANG Junxiong
climatic variation tendencies, interdecadal variations,
and climate jumps over the middle reaches of the
Yarlung Tsangpo River in the Tibetan Plateau (Zhou
et al., 2001), and the climate variations, tendencies,
and climate jumps in Xinjiang Autonomous Region
(Yang, 2003), etc. However, few studies on the climate tendencies and abrupt changes in the upper Yellow River Basin have been done, although Yang and
Li (2004b) analyzed the abrupt and periodic changes
of the precipitation and runoff series in this area with
EOF method and Mann-Kendall method. Therefore,
further study should be conducted. In addition, the
scarcity of water resources in the Yellow River Basin
has been paid more attention to by domestic and international experts in recent years. Headwater catchment
of the Yellow River Basin is the “water tower” of the
whole basin, in which the streamflow has reduced, and
the water level in the lakes has declined. Whether it resulted from climate change or human activities should
be further studied. Therefore, on the basis of monthly
mean air temperature, precipitation, sunshine duration, and evaporation from 23 meteorological stations
in the upper Yellow River Basin (upward of Lanzhou
Station) from 1960 to 2001, the feasibility of using
hypothesis test techniques to identify the long-term
trend for major climate variables during the past 42
years has been investigated in this study. At the same
time, the abrupt changes also have been examined by
using different methods to quantitatively describe the
climate change in the study area.
2. Study area
The Yellow River Basin is located in the semi-arid
and semi-humid region with severe water scarcity, in
which the annual mean precipitation is about 200-600
mm, and the natural streamflow is about 580×108 m3
(Yang and Li, 2004b). The drainage area at upward of
Lanzhou Station is about 222551 km2 . The climate belongs to the Qinghai-Tibetan Plateau climate system.
In cold seasons, the basin climate has the characteristics of typical continental climate, which is controlled
by the high pressure of the Qinghai-Tibetan Plateau,
lasting for about seven months. In warm seasons, the
climate is affected by southwest monsoon, producing
205
heat low pressure, with abundant water vapor and
more precipitation, and thus forms the plateau subtropical humid monsoon climate. The whole climate
characteristics of the study area are as follows: long
winter nearly without summer, spring immediatly after autumn, low heat, small annual temperature difference, large daily temperature range, long sunshine
duration, intense solar radiation, big windy storm, and
short plant growth periods. The annual air temperature is 2.68◦ C, with 2554.7 h for sunshine duration,
1428.9 mm for evaporation, and 446 mm for precipitation. The annual precipitation shows an increasing trend from northwest to southeast. The precipitation from June to September accounts for 75% of
the annual value. The water resources of the upper
Yellow River Basin account for 57.5% of the whole
Yellow River Basin (average of 1951-1998), in which
the spatio-temporal variations of the water resources
are very important for the whole Yellow River Basin
(Li, 2003). The variation of climate variables are
the main reasons for the water resources change (Li,
2003). Therefore, it is very important to investigate
the spatio-temporal variations of climate variables in
the upper Yellow River Basin in order to identify the
evolvement of the water resources system in the whole
Yellow River Basin.
3. Data and methodology
There are 23 meteorological stations selected in
the upper Yellow River Basin. These stations are spatially well distributed, which can reflect the characteristics of regional climate. The data of monthly mean
air temperature, precipitation, sunshine duration, and
evaporation come from the China Meteorological Administration, which have been checked by the primary
quality control. Considered the reliability and integrality, the observed data from 1960 to 2001 are selected in this study. At the same time, in order to
ensure the integrality of the time series, the absent
data are interpolated by using the data from nearby
stations. From the statistical meaning, it is credible
to get the results by the use of so long time series.
The location of the study area and the meteorological
stations selected are shown in Fig.1.
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ACTA METEOROLOGICA SINICA
Fig.1. Location of the study area and the
meteorological stations selected.
According to the unique climate characteristics
in the upper Yellow River Basin, the seasons can
be classified as follows: March-April-May for spring,
June-July-August for summer, September-OctoberNovember for autumn, and December-JanuaryFeburary (the following year) for winter (Zeng, 2004).
For the time series of each season, the data of mean air
temperature is the average of three months’ value, but
the precipitation, sunshine duration, and evaporation
are the sum of three months’ value. In order to reduce
the unilateralism of single station record, the regional
series are calculated by the spatial average of all the
stations in the whole area. When analyzing the climate abrupt changes, the 5-yr moving average series
of the regionalized data for seasonal and annual series
are estimated, which represents the long-term trends.
In this study, the climate tendencies in the study
area are analyzed by using nonparametric MannKendall method, the periodic changes are analyzed by
using departure curve method, and the climate abrupt
changes are analyzed by use of moving T method, Yamamoto method, and Mann-Kendall method.
4. Climate change analysis
During the past 20 years, many researchers have
investigated the regional climate characteristics on different time scales in China. The results provide favorable basis and direction to exactly grasp the climate
characteristics on large scale and further understand
the regional climate change (Yan et al., 2001). Nonparametric Mann-Kendall method is widely used to
analyze the trends of the environmental time series,
VOL.21
which is recommended by World Meteorological Organization (WMO) (Liu and Zheng, 2003, 2004; Yu et
al., 2002). It is also an efficient tool to examine the
monotonic trend of hydro-meteorological series (Xu et
al., 2002, 2003). In this study, the climate trends of
climate variables from 23 gauging stations in the upper Yellow River Basin for 42 yr are detected at the
95% level of significance in this study. At the same
time, the magnitude of long-term trend for climate
variables (Kendall slope) from different gauging stations are spatially interpolated in this study in the
whole basin by using Kriging method.
4.1 Temperature
Figure 2a shows the spatial distribution of nonlinear tendency for the mean air temperature in the
upper Yellow River Basin. It shows an increasing
trend in most parts of the study area. The Kendall
slopes at 21 gauging stations are positive, and only 2
stations (Zhongxin and Henan Stations) are negative.
Two warm centers are shown in the whole basin: one
is near Qiabuqia Station in the north, and the other is
near Lanzhou Station in the east, in which the Kendall
slopes are up to 0.48◦C/(10 yr) and 0.44◦ C/(10 yr),
respectively. The average Kendall slope for the whole
basin is 0.18◦C/(10 yr), i.e., the mean air temperature has increased by 0.76◦C in the upper Yellow River
Basin during the past 42 years.
Figure 2b shows the departure curves of the mean
air temperature in the upper Yellow River Basin. Departure is the difference of climate variables for 42 yr.
It is shown in Fig.2b that there are two obvious periods
in the study area for the past 42 years. One is the cold
period of 1960-1986, in which the negative departures
account for more than 80%, and the abnormal cold
years are 1967, 1977, and 1983, respectively. The other
is the short warm period of 1987-2001, in which the
mean air temperature is 3.1◦ C, 0.46◦C higher than the
average of the whole basin. In warm period, the negative departures account for more than 87%, in which
the highest temperature for 42 yr, and the temperature
in 1998 is 1.7◦ C higher than that of the whole basin.
The temperature change has an obvious seasonal difference. Comparing with the departure curves, winter
temperature has major contribution to the annual
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ZHAO Fangfang, XU Zongxue and HUANG Junxiong
207
Fig.2. Distribution of nonlinear tendency for temperature: (a) spatial distribution ( ◦ C/10 yr) and (b)
departure curves (◦ C).
mean temperature. This conclusion is consistent with
the result obtained by Ding and Dai (1994).
4.2 Precipitation
Figure 3a shows the distribution of nonlinear tendency for precipitation in the upper Yellow River
Basin. It shows a decreasing trend in most parts of
the basin. The Kendall slopes at 17 gauging stations
are negative. There are two decreasing centers located
near Lintao and Henan Stations along the main stem,
in which the Kendall slopes are −28.63 mm/(10 yr)
and −28.83 mm/(10 yr), respectively. The average
Kendall slope for the whole basin is −4.26 mm/(10
yr). Therefore, there is a slight dry trend in the upper
Yellow River Basin since 1960.
Figure 3b shows the departure curves of the precipitation in the upper Yellow River Basin. It is shown
that the departure curve fluctuates significantly, with
the characteristics of three increasing and three de-
creasing abrupt changes since the 1960s. The period of
more precipitation i. e., 1970-1989, lasts for long time,
in which the mean precipitation is 11.7 mm more than
that of the whole basin. The period of less precipitation is from 1990 to 2001, in which the mean precipitation is 18.6 mm less than that of the whole basin.
The seasonal departure curves show that autumn precipitation has the greatest contribution to the annual
total.
4.3 Sunshine duration
Figure 4a shows the distribution of nonlinear tendency for annual sunshine duration in the upper Yellow River Basin. It shows a decreasing trend in most
parts of the study area. The decreasing center is located at Minhe and Lanzhou Stations, in which the
greatest Kendall slope is up to −104.38 h/(10 yr).
Meanwhile, the increasing area centered at Tongde
Fig.3. Distribution of nonlinear tendency for precipitation: (a) spatial distribution (mm/10 yr) and (b)
departure curves (mm).
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ACTA METEOROLOGICA SINICA
Dari, and Maqu Stations, with the greatest Kendall
slope up to 56.39 h/(10 yr). The average Kendall
slope for the whole basin is −29.9 h/(10 yr), i.e., the
sunshine duration decreased by 125.6 h in the upper
Yellow River Basin during the past 42 years.
Figure 4b shows the departure curves of the sunshine duration in the upper Yellow River Basin. There
are two obvious periods. One is the higher period from
1961 to 1980 lasting for long time, in which the sunshine duration is 35.4 h higher than that of the whole
basin. The other is the lower period from 1981 to
1996, in which the sunshine duration is 49.4 h lower
than that of the whole basin. In the seasonal trend
curves, the spring and winter sunshine durations make
the greatest contribution to the annual total.
4.4 Evaporation
Figure 5a shows the distribution of nonlinear tendency for annual pan evaporation in the upper Yellow River Basin. It shows a decreasing trend in most
parts of the study area, in which the greatest Kendall
slope is −115.74 mm/(10 yr). In the eastern, southern,
and western marginal area, the evaporation shows an
increasing trend. The average Kendall slope for the
whole basin is −38.4 mm/(10 yr), i.e., the evaporation decreased by 161.3 mm in the upper Yellow River
Basin during the past 42 years.
Figure 5b shows the departure curves for the pan
evaporation in the upper Yellow River Basin. There
are an obvious increasing period from 1960 to 1973
and an obvious decreasing period from 1974 to 1997.
The pan evaporation is 74 mm higher in the increasing
period and 50 mm lower in the decreasing period than
the average. In the seasonal trend curves, the spring
and summer pan evaporation has significant contribution to the annual value.
4.5 Relationship among major climate variables
The interdecadal variations for the departure time
series of the mean air temperature, precipitation, sunshine duration, and pan evaporation are shown in
Figs.2b, 3b, 4b, and 5b with dashed lines. It is shown
VOL.21
in Figs.2b and 3b that the temperature in the 1960s
and 1980s are increasing, and the precipitation is increasing from the 1960s to 1980s, but deceasing in
the 1990s. The relationship between precipitation and
temperature is weak, i.e., the precipitation may be
high or low when the temperature is high. The result is similar to that obtained by Shi (1996), i.e., the
changes of temperature are not directly responsible
for the changes of precipitation. Therefore, the variations of precipitation in the future should be further
studied. The sunshine duration is one of the important climate factors to evaluate the regional radiation
resources. In principle, decreasing of the sunshine duration may result in decreasing of temperature. However, the green house effect leads to the increasing of
temperature (Yang et al., 2004). The impact of human activities in the upper Yellow River Basin is relatively small. Therefore, there is inverse relationship
among sunshine duration, evaporation, and precipitation. It is shown in Fig.4b that sunshine duration has
decreased since the 1960s, especially in the 1980s, and
began to increase in the 1990s. The variations of evaporation (Fig.5b) are the same as that of the sunshine
duration, which is opposite to the inter-decadal variations of the precipitation as shown in Fig.3b.
It is the basis of eco-environmental change in the
study area to qualitatively analyze the relationship between temperature, precipitation, sunshine duration,
and evaporation. It can help to reasonably predict the
future climate changes and establish the corresponding countermeasures.
5. Abrupt changes of climatic variables
Climate system is nonlinear and discontinuous.
Therefore, it is necessary to analyze and understand
the change process of the climate system by using nonlinear theories and methods, such as theory of the
abrupt changes and the detection method (Yan et al.,
2003). Fu and Wang (1992) discussed the definition
and detection methods, which can help to understand
and detect the abrupt changes.
There are many kinds of methods to detect the
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ZHAO Fangfang, XU Zongxue and HUANG Junxiong
209
Fig.4. Distribution of nonlinear tendency for sunshine duration: (a) spatial distribution (h/10 yr) and (b)
departure curves (h).
Fig.5. Distribution of nonlinear tendency for pan evaporation: (a) spatial distribution (mm/10 yr) and (b)
departure curves (mm).
abrupt changes, such as low pass filtering method,
moving T test method (MTT method), Crammer
method, Yamamoto method, Mann-Kendall method,
Spearman method, etc. The low pass filtering method
is not applicable. MTT method, Crammer method,
and Yamamoto method are famous for intuitionistic,
simple, and convenient uses. But the results may be
different because of the artificial reasons. Therefore,
it should depend on the Mann-Kendall method and
Spearman method to accurately examine the occurrence of abrupt changes. These methods have merits
of broad detecting range, small artificial impact, and
high quantitative degree (Wei, 1999). Therefore, the
abrupt changes of the climate variables in the study
area are detected by using MTT method, Yamamoto
method, and Mann-Kendall method. The detailed
theories are referred to Fu and Wang (1992) and Wei
(1999).
Wei and Cao (1995) analyzed the abrupt changes
of mean air temperature in China, Northern Hemisphere, and global area, and got the results that it is
creditable when 10-yr mean period is taken for the
abrupt index. Therefore, the mean period of time
n1 =n2 =10 is adopted in this paper, and n1 =n2 =14 as
the comparing period. However, only abrupt changes
occurring in 1967-1991 were detected with these two
mean periods. Based on these ideas, the abrupt
changes of climate variables are detected in terms of
5-yr moving seasonal and annual time series of temperature, precipitation, sunshine duration, and pan
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ACTA METEOROLOGICA SINICA
evaporation in the upper Yellow River Basin.
The t statistics of mean temperature, precipitation, and sunshine duration in the upper Yellow River
Basin are at the 1% level of significance in 1985, 1987,
and 1982, respectively (see Figs.6a, b, and c). It shows
that an abrupt warming occurred in the late 1980s
in the study area, which is somewhat consistent with
that obtained by You (1998). An abrupt change of
the annual precipitation occurred in the mid-1980s and
an abrupt change of the sunshine duration took place
in the early 1980s. Although the abrupt changes of
the mean temperature happened in spring of the early
1970s and winter of the late 1960s and early 1970s,
there is no statistical significance. In the same way,
the abrupt changes of precipitation occurred in summer of the 1970s and in winter of the late 1960s and
early 1970s, but it is not up to the corresponding level
of significance. Figure 6d shows that there is an obvious increasing trend for annual pan evaporation in the
1960s-1980s, and there is an abrupt change from high
value to low values in the early 1980s. In addition, the
t statistic is over 1% level of significance (negative) in
the early 1990s, i.e., there is also a significant abrupt
change from low to high values for annual evaporation
in the same period.
The abrupt changes detected by using Yamamoto
method are listed in Table 1. Two mean periods of
time n=10 and n=14 are used in this study. It is shown
VOL.21
that there are abrupt changes for sunshine duration in
all seasons except autumn. For other three climate
variables, the abrupt changes occurred in all four seasons, especially acute jumps for annual mean temperature, winter precipitation, and spring pan evaporation.
In the 1960s, the abrupt changes occurred for the mean
air temperature, precipitation, and evaporation in the
upper Yellow River Basin, of which the abrupt changes
of the evaporation occurred in spring, winter, and the
whole year, but only in winter for the mean air temperature and precipitation. It is mainly because the time
series are too short in this study. However, it can also
be understood that the abrupt changes of the climate
variables occurred in the upper Yellow River Basin in
the 1960s. In different periods of the 1970s, the abrupt
changes were detected for the mean air temperature,
precipitation, sunshine duration, and evaporation in
the upper Yellow River Basin, in which the abrupt
changes were detected in four seasons and the annual
series for evaporation, and in the summer and winter
for precipitation. One acute abrupt change was detected in the winter of 1971, with signal-noise ratio
(S/N ) of 2.1. In addition, some abrupt changes were
detected in the same period for spring temperature
and summer sunshine duration. Compared with the
abrupt changes in the 1960s and 1970s, the climate
jumps in the 1980s are most significant. These
results are similar to the results detected in the
Fig.6. The moving t-statistic curve of the climatic factors in the upper Yellow River Basin. (a) Temperature,
(b) precipitation, (c) sunshine duration, and (d) evaporation; dashed lines: α=0.01.
NO.2
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ZHAO Fangfang, XU Zongxue and HUANG Junxiong
Qinghai-Tibetan Plateau (Tang et al., 1998). The
abrupt changes were examined for major climate variables in different seasons and annual series of the
1980s, except for the spring mean temperature, summer precipitation, summer sunshine duration, and
summer and winter evaporations. About 47% of the
maximum values of S/N happened in this period.
In addition, the acute abrupt changes happened for
spring evaporation in 1981 and for the annual air temperature in 1985, and the values of S/N are 2.19 and
2.02, respectively.
Figure 7 shows the S/N values of annual time
series for four climatic factors. The phases of S/N
values for the pan evaporation abrupt changes are obviously ahead of other climate factors. The abrupt
changes of the evaporation mainly occurred in the
1970s. However, the phases of S/N values for other
factors mainly occurred in the 1980s. Different climate
factors were detected with different S/N values of the
abrupt changes. The abrupt changes can be detected
in 1971-1987 simultaneously using the two mean periods of time, with the similar results. However, the
abrupt changes of climate factors can not be detected
before 1971 and after 1987 when n=14 because of the
limited time series.
For the upper Yellow River Basin, the abrupt
changes of four climate factors did not exhibit consistent rules. This is mainly due to the different seasonal changes for four climate factors. For example,
the abrupt changes of the precipitation, sunshine duration, and evaporation showed better association in
the mid-1970s, i.e., the summer precipitation increased
and the summer sunshine duration and evaporation
decreased.
Table 2 lists the abrupt changes for regional annual and seasonal time series detected by using MannKendall method for four climate factors in the upper Yellow River Basin, with the corresponding years
shown in Fig.8. It is shown that the abrupt changes of
mean air temperature mainly occurred in the 1990s,
which is corresponding to the results for global warming period of 1990-1991 (Wei et al., 1995). The abrupt
changes of autumn precipitation were detected in 1986,
which is similar to the results obtained by Yang and
Li (2004a). In addition, the abrupt changes of evaporation mostly occurred in the 1960s and the abrupt
changes of the sunshine duration primarily took place
in the 1980s.
Table 1. Climate jumps detected by using Yamamoto method in the upper Yellow River Basin during the period
of 1960-2001
Time
n values
Periods
Spring
Summer
Years of
max.S/N
Periods
Years of
max.S/N
Periods
Autumn
Winter
Annual
Mean temperature
Precipitation
n=10
n=14
n=10
1973-1974 1973-1975 1981-1983
n=14
Sunshine duration
n=10
n=14
1982-1986 1981-1985
Pan evaporation
n=10
1967-1968,1971
1989-1991
1991
1979-1983,1991
1.14(1974) 1.39(1974) 1.4(1982)
1.71(1984) 1.62(1983) 1.54(1967), 1.04(1971)
1.89(1991)
1.14(1991)
2.19(1981), 1.53(1991)
1985-1991 1986-1987 1972-1976 1973-1974 1973-1979 1976-1980 1972-1981, 1989-1991
1.37(1987) 1.37(1987) 1.28(1973) 1.06(1974) 1.23(1973) 1.15(1979) 1.7(1973), 1.22(1991)
1984-1988 1979-1987 1983-1988 1983-1986
1991
Years of 1.65(1986) 1.45(1987) 1.75(1984)
max.S/N 1.10(1991)
1969-1970 1983-1987 1969-1974
Periods
1983-1986
1985-1988
Years of 1.27(1970) 1.61(1985) 2.1(1971)
max.S/N 1.65(1985)
1.85(1986)
1984-1988 1984-1987 1985-1991
Periods
1991
Years of 2.02(1985) 1.43(1987) 1.59(1987)
max.S/N 1.03(1991)
1972,1984-1985
1.42(1985)
1972-1974 1982-1986
1982
1986
1.37(1973) 1.48(1985) 1.01(1982)
1.00(1986)
1986-1987 1981-1985 1980-1983
n=14
1971-1974
1978-1983
1.22(1971)
1.66(1981)
1971-1980
1.7(1973)
1.7(1974)
1971-1972
1990-1991
1985-1987
1.03(1972),1.13(1984) 1.09(1971)
1.15(1991)
1.13(1987)
1967-1974
1971-1973
1.33(1971)
1.44(1971)
1967,1971-1975
1971-1981
1978-1982,1990-1991
1.68(1987) 1.32(1982) 1.45(1981) 1.12(1967), 1.33(1973) 1.45(1973)
1.61(1981), 1.61(1991) 1.45(1980)
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ACTA METEOROLOGICA SINICA
VOL.21
Fig.7. S/N values of annual time series for four climatic factors for (a) n=10 and (b) n=14.
The comparison of the results obtained by Ya-
those detected by using Yamamoto method, in which
mamoto method with those obtained by Mann-
the abrupt changes could not be detected by using
Kendall method exhibited that some of the abrupt
Mann-Kendall method for mean air temperature in the
changes detected by using two methods were quite
1980s, sunshine duration in the 1970s, and pan evap-
similar, especially the sunshine duration in the 1980s.
oration in the 1970s and 1980s. Different detection
However, some abrupt changes detected by using
methods may get different results, and each method
Mann-Kendall method, including pan evaporation in
has its own virtues and shortages (Fu et al., 1992; Yan
the 1960s and mean temperature and precipitation in
et al., 2001). Figure 8 shows the abrupt changes of cli-
the 1990s, could not be detected by Yamamoto method
matic factors detected by using Mann-Kendall method
because of the limited data. The abrupt changes de-
at a significance level of 5% in the study area.
tected by using Mann-Kendall method are only 50% of
Table 2. The years with climate jump detected by using Mann-Kendall method in the upper Yellow River Basin
Time
Mean temperature
Precipitation
Pan evaporation
Sunshine duration
Spring
1998
-
1968
1984
Summer
1997
-
1965
1977
Autumn
1995
1986
-
-
Winter
1986
1975
1969
1982
Annual
1994
1994
1965
1981
Fig.8. Jump of climatic factors detected by using Mann-Kendall method in the upper Yellow River Basin.
(a) Temperature, (b) precipitation, (c) sunshine duration, and (d) evaporation; dashed lines: α=0.05.
NO.2
ZHAO Fangfang, XU Zongxue and HUANG Junxiong
6. Discussions and conclusions
Some conclusions can be drawn by analyzing the
climate data in the upper Yellow River Basin from
1960 to 2001.
(1) Mean air temperature: There are two increasing centers in the study area: one is near Qiabuqia
Station in the north, and the other is near Lanzhou
Station in the east. The Kendall slope of the mean
air temperature is 0.18◦ C/(10 yr) in the whole area,
increasing by 0.76◦ for 42 yr. The winter temperature
has the greatest contribution to the annual total. The
detection results show that there is an obvious abrupt
warming occurring in the late 1980s. An acute abrupt
change was detected by using Yamamoto method in
1985.
(2) Precipitation: The climate exhibits a dry
tendency in the upper Yellow River Basin since the
1960s. The mean Kendall slope of precipitation is
−4.26 mm/(10 yr) for the whole basin. The winter
precipitation has the greatest contribution to the annual total. The detecting results show that there is an
obvious abrupt change for precipitation in the mid1980s, changing from wet to dry.
(3) Sunshine duration: The Kendall slope of annual sunshine duration is −29.9 h/(10 yr). There are
two obvious periods: one is the high period of 19611980, and the other is the low period of 1981-1996.
An obvious abrupt change occurred in the early 1980s,
changing from high to low value.
(4) Pan evaporation: The annual evaporation decreased by 161.3 mm for the past 42 years, in which
the spring and summer evaporation have great contribution to the annual evaporation. In the results
obtained by using MTT method, two abrupt changes
occurred in the 1980s and the early 1990s. The test results obtained by using the Yamamoto method show
that the abrupt changes of evaporation mainly occurred in the 1970s. According to the Mann-Kendall
method, the abrupt changes mostly occurred in the
1960s.
In conclusion, there is a warm and dry tendency
in the upper Yellow River Basin for the past 42 years,
i.e., increasing temperature and decreasing precipitation. One interesting phenomenon is that there is
213
a decreasing trend for evaporation in the study area
during the past 42 years, although the temperature
is increasing. This may result from possible climate
change or the impact of human activities. It should
be pointed out that it is not easy to distinguish from
abrupt changes and monotonic trends, and thus further investigation is required to identify these trends
more precisely. However, it is confident that the approaches presented in this paper may be useful tools
for further examining the impact of climate change on
hydrological processes.
REFERENCES
Ding Yihui and Dai Xiaosu, 1994: Temperature variation
in China during the last 100 years. Meteorological
Monthly, 20(12), 19-26. (in Chinese)
Fu Congbin and Wang Qiang, 1992: The definition and
detection of the abrupt climatic change. Scientia
Atmospherica Sinica, 16(4), 482-493. (in Chinese)
Li Chunhui, 2003: The reproducible evaluation of the
surface water resources in the Yellow River Basin.
Dissertation, Beijing Normal University. (in Chinese)
Li Daofeng, 2003: Impact of climate and land-cover
change on runoff of the source regions of the Yellow
River. Dissertation, Beijing Normal University. (in
Chinese)
Li Yueqing, 2001: A phase space EOF method and its
application to climate diagnosis. Plateau Meteorology, 20(1), 88-93. (in Chinese)
Liu Changming and Zheng Hongxing, 2004: Changes in
components of the hydrological cycle in the Yellow
River Basin during the second half of the 20th century. Hydrological Processes, 18, 2337-2345.
Liu Changming and Zheng Hongxing, 2003: Trend analysis of hydrological components in the Yellow River
Basin. Journal of Natural Resources, 18(2), 129135. (in Chinese)
Shi Yafeng, 1996: Chinese Historical Climatic Changes.
Shandong Science & Technology Press, 443-467. (in
Chinese)
Tang Maocang, Bai Chongyuan, Feng Song, and Caiying, 1998: Climate abrupt change in the QinghaiTibetan Plateau in recent century and its relation
to astronomical factors. Plateau Meteorology, 17(3),
250-257. (in Chinese)
Wang Shaowu, 1997: Scientific intersection of PAGES
and CLIVAR. Acta Meteorologica Sinica, 55(6),
214
ACTA METEOROLOGICA SINICA
662-669. (in Chinese)
Wei Fengying and Cao Hongxing, 1995: Detection of
abrupt changes and trend prediction of the air temperature in China, the Northern Hemisphere and
the globe. Scientia Atmospherica Sinica, 19(2),
140-148. (in Chinese)
Wei Fengying, 1999: Modern Technology of Statistics,
Diagnosis and Forecast for Climate. China Meteorological Press, 62-76. (in Chinese)
Xu Z. X., K. Takeuchi, and H. Ishidaira, 2002: Long-term
trends of annual temperature and precipitation time
series in Japan. Journal of Hydroscience and Hydraulic Engineering, 20(2), 11-26.
Xu Z. X., K. Takeuchi, and H. Ishidaira, 2003: Monotonic
trend and step changes in Japanese precipitation.
Journal of Hydrology, 279, 144-150.
Yan Minhua, Deng Wei, and Chen Panqin, 2003: Analysis of climate jumps in the Sanjiang Plain. Scientia
Geographica Sinica, 23(6), 661-667. (in Chinese)
Yan Minhua, Deng Wei, and Ma Xuehui, 2001: Climate
variation in the Sanjiang Plain disturbed by large
scale reclamation during the past 45 years. Acta
Geographica Sinica, 56(2), 159-170. (in Chinese)
Yan Zhongwei, Ji Jinjun, and Ye Duzheng, 1990a: The
climatic jump of the Northern Hemisphere in summer during the 1960s. I: Precipitation and temperature change. Chinese Science (B), 1, 97-103. (in
Chinese)
Yan Zhongwei, Ji Jinjun, and Ye Duzheng, 1990b: The
climatic jump of the Northern Hemisphere in summer during the 1960s. II: Sea level pressure and 500
hPa height change. Chinese Science (B), 8, 879-885.
(in Chinese)
Yan Zhongwei, 1992: A primary analysis of the process
of the 1960s Northern Hemispheric summer climatic
VOL.21
jump. Scientia Atmospherica Sinica, 16(1), 111119. (in Chinese)
Yang Lianmei, 2003: Climate change of extreme precipitation in Xinjiang. Acta Geographica Sinica, 58(4),
577-583. (in Chinese)
Yang Yanwu, Yu Qiang, and Wang Jing, 2004: Spatiotemporal variations of principal climatic factors in
North China and part of East China within the past
40 years. Resources Science, 26(4), 45-50. (in Chinese)
Yang Zhifeng and Li Chunhui, 2004a: Abrupt and periodic changes of the annual natural runoff in the
subregions of the Yellow River. Journal of Mountain
Science, 22(2), 140-146. (in Chinese)
Yang Zhifeng and Li Chunhui, 2004b: The spatial and
temporal structure of precipitation in the Yellow
River Basin. Progress in Geography, 23(2), 27-33.
(in Chinese)
You Weihong, 1998: Multi-scale Diagnosis of Climatic
Change and Some Technologies and Methods for Its
Forecast. China Meteorological Press, 1-17. (in Chinese)
Yu, P. S., T. C. Yang, and C. K. Wu, 2002: Impact of
climate change on water resources in southern Taiwan. Journal of Hydrology, 260, 161-175.
Zeng Yan, 2004: Distributed modeling of actual evapotranspiration over rugged terrain of the Yellow River
Basin. Dissertation, Chinese Academy of Sciences.
(in Chinese)
Zhou Shunwu, Jia La, and Du Jun, 2001: Analyses of
climatic trend and jump over the middle reaches of
Yarlung Tsangpo River in the Tibetan Plateau in
recent 42 years. Plateau Meteorology, 20(1), 71-75.
(in Chinese)