Journal of the Meteorological Society of Japan, Vol. 90C, pp. 1--16, 2012
1
doi:10.2151/jmsj.2012-C01
A China-Japan Cooperative JICA Atmospheric Observing Network
over the Tibetan Plateau (JICA/Tibet Project): An Overviews
Renhe ZHANG
State Key Laboratory of Severe Weather (LaSW), Chinese Academy of Meteorological Sciences, Beijing, China
Toshio KOIKE
Department of Civil Engineering, the University of Tokyo, Tokyo, Japan
Xiangde XU
State Key Laboratory of Severe Weather (LaSW), Chinese Academy of Meteorological Sciences, Beijing, China
Yaoming MA and Kun YANG
Institute of the Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China
(Manuscript received 1 April 2011, in final form 12 September 2011)
Abstract
Because of the importance of the impact of the Tibetan Plateau on atmospheric general circulations and climate across China, Asia, and even the world, Chinese and Japanese scientists jointly constructed an integrated
atmospheric observing system, especially for the water vapor observation, across the Tibetan Plateau and its adjacent areas during the period of 2005–2009 under the JICA (Japan International Co-operation Agency) project
(JICA/Tibet Project). The JICA/Tibet Project aims at understanding processes of the land-atmosphere interaction over the Tibetan Plateau and their impacts on the severe weather and climate over the Tibetan Plateau and
the area to its east in the East Asian region. The project is designed in an attempt to alleviate impacts of meteorological disasters in these areas through improving the prediction skill.
The implementation of the project has enhanced the capability of monitoring the Plateau atmosphere. The
numerical forecast techniques are developed through assimilating observed data into the numerical model. Based
on the investigation of observed surface energy balance, the land surface model is improved. It is found that the
diurnal variation of precipitation over the Plateau is closely related with water vapor, and the latent heat release
is a main factor a¤ecting the Plateau vortex. By analyzing observed seasonal features of the tropopause, the
evidence of strong stratosphere and troposphere exchange over the Tibetan Plateau is provided. It reveals that
the interannual variability of summer rainfall in East China corresponds to that of vegetation index over the
Plateau. The crossing hemispheric circulations driven by the thermal and mechanical forcings of the Plateau
play an important role in water vapor transports not only over East Asia, but also in the global scale.
1. Background and motivation
Corresponding author: Renhe Zhang: Chinese Academy of Meteorological Sciences, No. 46 Zhong-GuanCun South Ave., Haidian District, Beijing 100081,
China.
E-mail: [email protected]
6 2012, Meteorological Society of Japan
The Tibetan Plateau sits in the subtropical area
within 25 N–40 N, 74 E–104 E in the middle of
Asia. It is the highest plateau in the world, with
extremely complex terrains. The Plateau’s averaged
elevation ranges between 4,000 m and 5,000 m
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above sea level and thus is also called ‘the roof
of the world’, or ‘the third pole’. The Plateau is
bounded on the east by the Hengduan Mountains,
with the Himalaya Range bordering the south and
west, and the Kunlun Mountains the north. Most
part of the Plateau sits in the southwest part of
China, including the Xizang Autonomous Region,
Qinghai Province, the west part of Sichuan Province, the southern part of Xinjiang Uygur Autonomous Region, and parts of Gansu Province and
Yunnan Province. Geographically, it also covers
part of Bhutan, Nepal, India, Pakistan, Afghanistan, Tajikistan, and Kyrgyzstan. The Plateau occupies an area of 2.5 million square kilometers,
with 2.4 million square kilometers standing within
the territory of the People’s Republic of China.
The Tibetan Plateau is a huge piece of land jutting out of the earth surface, stretching up to the
middle troposphere. As a result, the temperature,
humidity, air pressure and other meteorological
elements over the Plateau are noticeably di¤erent
from the ones in the surrounding free atmosphere.
In the boreal summer, the Plateau is an immense
heat source in the middle troposphere, and a cold
source in the boreal winter (Ye and Gao 1979). Its
thermal and dynamical e¤ects cast a major impact
on the formation and evolution of atmospheric circulations and climate across China, Asia, and even
the world (Ye et al. 1957, 1998; Huang 1985; Yanai
et al. 1992). The vortex formed up above the Plateau and its eastward moving can produce a critical
e¤ect on the heavy rains occurred in the east part of
China. For example, an extraordinary heavy rain
that attacked North China in 1963, and an extraordinary flush flood that swept across the Yangtze
River valley in 1954 were associated with the eastbound movement of vortexes stemmed from the
Plateau (Tao and Ding 1981). The dynamic and
thermal e¤ects of the Plateau play a key role in the
water vapor transportation to the Yangtze River
valley during the Meiyu period in China (Xu et al.
2002). The Plateau’s sensible heat driven air pump
(SHAP) e¤ect not only sustains the summer monsoons in Asia, but also a¤ects global climate by
inducing up a Rossby wave train (Wu et al. 1997).
The e¤ects of the latent heat as well as the sensible
heat were also identified recently. Fujinami and
Yasunari (2001) investigated seasonal variations in
cloud activity over the Plateau, reporting significant
cloud activity in spring (March–April). Ueda et al.
(2003) also demonstrated the importance of condensation heating in the heat balance during the
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pre-onset phase of the summer monsoon over the
western Plateau. The first intensive in situ observations during early spring upon the Plateau were
performed in April 2004 under the framework
of the Coordinated Enhanced Observing Period
(CEOP) (Koike 2004). Based on in situ and satellite
observations, and numerical simulations, Taniguchi
and Koike (2007) reported the importance of cumulus activity in terms of increases in atmospheric
temperature in the upper troposphere, even in
April. In the boreal winter, the change of the heat
source across the Plateau may breed out abnormal
zonal winds over the equatorial Pacific Ocean,
which in turn may result in an abnormal sea surface
temperature that would eventually a¤ect ENSO
events (Chen et al. 2001).
In recent years, China has witnessed a raised frequency of meteorological disasters (China Meteorological Administration 2007). China has been
working hard to establish a well functioned meteorological observing network, in an attempt to meet
the needs of disaster prevention and reduction.
However, the operational meteorological stations
in the west part of the country are noticeably lower
in number, compared with the east part (Zhang
2006). The number of the meteorological stations
sitting across the Tibetan plateau, a region that
takes up about one fourth of the nation’s territory,
is extremely out of proportion to the vast area it
has covered, due to high elevation, tough natural
environment and di‰cult observation. The scarcity
of the observed data over such a vast area not only
compromises the scientific research, but also questions the reliability and accuracy of predictions of
high impact weather events across the Plateau and
the area to its east, the Yangtze River and Yellow
River valleys and other East Asian countries, in
particular. Taking into account the importance of
the Tibetan Plateau in studying and predicting the
evolution of weather and climate in China and in
East Asia as well, it is necessary to improve the capability and utility of the atmospheric watch across
‘the roof of the world’ and its adjacent areas, and
enhance China’s capabilities in severe weather prediction and disaster prevention and reduction.
Considering the importance of establishing an
integrated atmospheric observing system on the Tibetan Plateau, the joint observation and research
on the Tibetan atmosphere between Chinese and
Japanese governments were defined as one of key
cooperation topics in December 1999. In July 2002,
the Chinese Academy of Meteorological Sciences
July 2012
R. ZHANG et al.
(CAMS) submitted a JICA (Japan International
Co-operation Agency) project proposal to the Chinese Ministry of Science and Technology (MOST)
on atmospheric monitoring over the Tibetan Plateau. The proposed collaboration included providing new observing equipment from JICA, especially
GPS for water vapor observation, to set up an
integrated meteorological observing network covering the Tibetan Plateau and its adjacent areas, on
the basis of the existing equipment and facilities
available for observation. Chinese side was responsible for the operation of the equipment and associated maintenance. Chinese and Japanese scientists
worked jointly on observations, field experiments,
and developments of the numerical weather prediction (NWP) model in a collaborative manner. Chinese side sent its research and operational personnel
to study in Japan under the support of JICA. After
reviewing by both MOST and JICA, the proposed
project was endorsed by both Chinese and Japanese
authorities concerned in September 2004 as an o‰cial JICA project, which was named as ChinaJapan Meteorological Disaster Reduction Cooperation Research Center Project (hereafter referred
to as JICA/Tibet Project). As a major international
cooperation initiative launched by JICA in the area
of meteorology, the JICA/Tibet Project started
from August 2005 and ended in June 2009. Xu
et al. (2008a) have reported the construction of the
Plateau observing network. Here, after the finish of
the project, the present paper introduces the implementation of the project as a whole, and especially
the associated achievements. The objectives that the
project was designed to achieve are depicted in Section 2, and implementation phases and equipment
in Section 3. Section 4 gives the accomplishments
made by the project, and concluding remarks are
given in Section 5.
2. Objectives
The JICA/Tibet Project was designed to establish a new generation of atmospheric observing network, especially for the water vapor observation,
covering the Tibetan Plateau and its adjacent areas,
to apply the achievements from observations to the
meteorological operation, to understand the role of
the Tibetan Plateau in the genesis of severe weather
and climate, and to improve the NWP skill. To enhance the capability of monitoring the atmosphere
over the Tibetan Plateau and its neighborhood in
the east in a three-dimensional manner, the JICA/
Tibet Project aimed at establishing an integrated
3
atmosphere observing network, improving both the
quality and quantity of the meteorological data collected from said area; by e¤ectively utilizing the
meteorological data collected from the Plateau in
NWP models and developing a new generation of
severe weather forecast and warning system, the
project also aimed at enhancing operational capabilities of monitoring, predicting and assessment of
severe weather and climate over the Plateau and the
area to its east. Therefore, through enhancement
of the regional operational meteorological forecast
system, the losses caused by meteorological disasters were expected to be alleviated in the East Asian
region, including China and Japan.
The implementation of the JICA/Tibet Project
provided the needed support for studying the impacts of the Tibetan Plateau on climate variabilities, and on high-impact weather events in the east
low-lying areas, and in the world as well. The project has worked on the following major scientific
issues: 1) the role of the unique topography and
boundary layer structure of the Tibetan Plateau in
shaping up a unique atmospheric heat source associated with hydrologic cycles, 2) the magnitudes of
the energy and hydrologic cycles over the Tibetan
Plateau in shaping up severe weather and climate
in China as well as in East Asia, and 3) the convective systems over the Plateau and their impacts on
droughts and floods in the East Asia region.
The Observing System Research and Predictability Experiment (THORPEX) (Shapiro and Thorpe
2004), under the World Weather Research Programme (WWRP), initiated by the World Meteorological Organization (WMO) has a defined goal to
improve weather forecast techniques through developing applicable observation methodologies and
systems over sensitive areas. The Tibetan Plateau
is a strong signal area for the possible flood-causing
weathers in the east part of China, in particular, the
Yangtze River valley. In this context, establishing
an integrated atmospheric observing system covering the Plateau and its adjacent areas is a major
scientific e¤ort to sort out the sensitive areas applicable to raise the capability in predicting severe
weather in the eastern China, especially that causing floods across the Yangtze River valley. Severe
weather forecast is extremely important to securing
a smooth economic and social development, and to
safeguarding people’s lives and properties. Installing a range of modern observing equipment on
the Tibetan Plateau and its adjacent areas makes
an important part of China’s climate observing
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system (Zhang and Xu 2008) that is under construction. Meanwhile, the application of achievements derived from the observational experiments
in monitoring severe weather/climate and in improving NWP helps China raising its severe
weather/climate watch and prediction capabilities.
3. Implementation phase and equipment
The integrated atmospheric observing network
established under the JICA/Tibet Project has
mainly covered the southwest part of China in Xizang Autonomous Region, Yunnan Province and
Sichuan Province, including some parts of Qinghai
and Guizhou Provinces, Guangxi Zhuang Autonomous Region, and Chongqing municipality. In
total the project was implemented over the region
dealt with two autonomous regions, four provinces,
and one municipality in southwestern China, covering the Tibetan Plateau and its neighborhood in the
east, the upper reaches of Yangtze River valley.
3.1 Implementation phase
The JICA/Tibet Project was implemented in a
phased manner. Three phases were divided in the
implementation period from December 2005 to
June 2009. Phase I, running from December 2005
to September 2007, was designed to establish an
observing system, and to develop the needed numerical prediction models; Phase II, from October
2007 to August 2008, focused on applications of
the established observing system, and on improving the numerical prediction models; Phase III was
staged to measure the performance of the observing
system and numerical prediction models in the period of September 2008–June 2009.
To improve the understanding of the impact of
the Tibetan Plateau on East Asian summer monsoon and heavy rainfall process occurred in China,
intensive observation periods (IOPs) were staged in
2008 in three separate time periods. The IOPs were
designed with intensified upper air sounding activities from regular twice a day to 4 times a day. Period I (IOP1), from 24 February to 23 March 2008,
focused on the observation of atmospheric activities
over the Plateau and its adjacent areas prior to the
onset of the East Asian summer monsoon, intending to understand the linkage of conditions of
the Plateau atmosphere in late winter and early
spring with the summer monsoon followed. Period
II (IOP2), running from 20 April to 19 May 2008,
was staged to understand the atmospheric activities
before and after the onset of the East Asian sum-
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mer monsoon, focusing on the role of the Plateau
atmosphere in triggering up the onset of the East
Asian summer monsoon. The last part of the IOP
experiment, period III (IOP3), covering the period
from 20 June to 19 July 2008, was made to observe
features of atmosphere over the Tibetan Plateau
during the flood season in the eastern China, in an
attempt to understand their impacts on the rainfall
in the flood season.
3.2 Equipment
The integrated observing network established by
the JICA/Tibet Project was mainly built on a range
of existing facilities, including the meteorological
observing network possessed by China Meteorological Administration (CMA), the Tibetan Plateau
observing and experimental stations owned by the
Institute of the Tibetan Plateau Research, the Chinese Academy of Sciences (ITP), GPS stations
established by the State Bureau of Surveying and
Mapping of China (SBSM), and observing sites
equipped with the observing instruments provided
by JICA. The aforementioned facilities were employed to establish the integrated observing network mainly composed of GPS water vapor observations, automatic weather stations (AWS),
upper air soundings, wind profilers, and atmospheric planetary boundary layer (PBL) observing
systems. The observing equipment employed in the
JICA/Tibet Project and their geographic distributions are depicted as follows:
a. GPS water vapor observing network
The GPS water vapor observing network was
composed of 26 GPS units. 24 units were those
newly installed from JICA, and 2 were existing
ones owned by SBSM. The geographical distribution of the units is presented in Fig. 1a. Among 26
GPS water vapor observing units, 9 were deployed
in Xizang Autonomous Region, 7 in Yunnan Province, 7 in Sichuan Province, 1 in Guangxi Zhuang
Autonomous Region, 1 in Guizhou Province, and
1 in Chongqing municipality.
b. AWS observing network
The AWS network was made up of 72 AWS
units. Of them, 7 were unmanned AWS units newly
installed from those provided by JICA, mainly distribute over the scarcely populated areas on the
Plateau. CMA provided 58 units, and ITP 7 units.
The geographical distribution of AWS is presented
in Fig. 1b. Of the 72 AWS units, 27 sat in Xizang
Autonomous Region, 10 in Yunnan Province, 11
July 2012
R. ZHANG et al.
5
Fig. 1. Geographical distributions of (a) GPS stations and (b) AWS stations utilized in the JICA/Tibet
Project. Black and red dots represent the equipment provided by JICA and existing ones, respectively.
The name and elevation (numeral in bracket; unit: m) for each GPS station are shown in (a).
in Sichuan Province, 13 in Qinghai Province, 7 in
Guangxi Zhuang Autonomous Region, 3 in Guizhou Province, and 1 in Chongqing municipality.
stations is shown in Fig. 2a. Of these Stations, 6
were distributed in Xizang Autonomous Region, 6
in Yunnan Province, and 7 in Sichuan Province.
c.
d. Other equipment
In the observing network, 2 wind profilers, one
from the JICA and one from CMA, were employed.
One profiler was located in Xizang Autonomous
Region, and another one in Yunnan Province.
Upper air sounding network
The upper air sounding network had 19 sounding
stations. In addition to 14 stations possessed by
CMA, JICA contributed 5 GPS sounding stations.
The geographical distribution of upper air sounding
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Vol. 90C
Fig. 2. Geographical distributions of (a) radiosounding stations provided by JICA (black dots) and existing
ones (red dots), and of (b) wind profilers (five-pointed stars), PBL observing systems (circles) and the meteorological observing system for water surface (black dot). Black and red colors mark the equipment
provided by JICA and existing ones, respectively. Numeral in bracket is the elevation for each station
(unit: m).
Meanwhile, 6 atmospheric PBL observing systems
were applied in the network. JICA provided 4
units, CMA 1, and ITP 1, with 3 installed in Xizang Autonomous Region, 1 in Yunnan Province,
and 2 in Sichuan Province respectively. In addition,
JICA provided 1 set of the water surface meteorological observing system, which was installed on
the Erhai Lake in Yunnan Province. The geographic distribution of these equipment is shown in
Fig. 2b.
July 2012
R. ZHANG et al.
7
Table 1. Amount of equipment used in the atmospheric observing network of the JICA/Tibet Project provided by
JICA, CMA, ITP and SBSM.
Equipment type
JICA
CMA
ITP
SBSM
Total
2
26
GPS stations
24
AWS stations
7
58
Radiosounding stations
5
14
19
Wind profiler
1
1
2
PBL observing system
4
1
Water surface observing system
1
7
72
1
6
1
Table 2. Amount of equipment used in the atmospheric observing network of the JICA/Tibet Project in each province
(autonomous region or municipality) over the Tibetan Plateau and its adjacent areas. YN, SC, QH and GZ stand
for Yunnan, Sichuan, Qinghai and Guizhou provinces, respectively; GX and XZ for Guangxi Zhuang and Xizang
Autonomous Regions; and CQ for Chongqing municipality.
Equipment type
XZ
YN
SC
GPS stations
9
7
7
AWS stations
27
10
11
Radiosounding stations
6
6
7
Wind profiler
1
1
PBL observing system
3
1
Water surface observing system
1
All equipment employed in the integrated atmospheric observing network of the JICA/Tibet Project and their coming sources are given in Table 1,
and in Table 2 their distributions in each Province
(Autonomous Region or municipality) in the southwestern China.
4. Achievement highlights
The establishment of an integrated atmospheric
observing network under the JICA/Tibet Project
has enhanced China’s atmospheric monitoring capability over the Tibetan Plateau and its adjacent areas. It also improved China’s capability
of the operational warning and predicting of severe
weathers across the Plateau and the east part of
China. Noticeable progress has been achieved in
research and its operational applications.
4.1
Operationalization of the observing network
and database
A platform has been established to function in
transmission, processing and analysis of the ob-
QH
13
GX
GZ
CQ
Total
1
1
1
26
7
3
1
72
19
2
2
6
1
served data, and monitoring the integrated meteorological observing system over the Tibetan Plateau
and its adjacent areas. Its operational application
was realized and a real-time operational workflow
was established. The observed real-time data were
first received by four local centers at Provincial Meteorological Bureaus of Sichuan and Yunnan, and
the Meteorological Bureaus of Guangxi Zhuang
and Xizang Autonomous Regions, respectively.
The received real-time observational data at the
four local centers then were gathered at the Beijing
Center at CAMS, where data processing, quality
control, monitoring and distribution to users were
conducted. The statistics show that the real-time
data transmission rate has reached design target.
By September 2007 at the end of Phase I for establishing the observing system, the receiving rate of
the observed hourly data exceeded 90% from 26
GPS and 72 AWS units, including newly installed
24 GPS and 7 AWS units provided by JICA. The
observational data from wind profilers, PBL observing systems and the meteorological observing
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Journal of the Meteorological Society of Japan
Vol. 90C
Fig. 3. Correlation coe‰cients between the averaged total precipitable water observed by GPSs in the JICA/
Tibet Project and the precipitation lagged by 24 h in China in the period from 0000 UTC 10 January to 1200
UTC 2 February 2008. Shadings indicate correlation with significance level exceeding 0.05. (from Xu 2009)
system for water surface were continuously collected every 10 minutes. Quality control has been
applied to all observed data.
Utilizing the surface based in situ observations,
e¤orts have been made to correct satellite data by
applying the variational method (Weng and Xu
1999), resulting in a range of satellite remote sensing products involving soil moisture, snow cover,
vegetation, cloud cover, rainfall, air temperature,
and water vapor over the Tibetan Plateau. Therefore, the JICA/Tibet Project established a database containing not only surface based in situ observational data, but also satellite remote sensing
products. The data produced by JICA/Tibet Project are archived at CAMS. Since the project
joined the AMY (Asian Monsoon Years 2007–
2012) Program, all data are available publicly following the AMY Data Release Guidelines (http://
www.wcrp-amy.org/).
4.2
An operational platform for warning and
predicting severe weathers
In order to investigate the role of the data collected in the JICA/Tibet Project in severe weather
in East China, the observed data were used in
diagnosis and numerical modeling of the severe
weather. During the implementation of the project,
heavy snowstorms occurred in the southeastern
China in the beginning of 2008 (Wen at al. 2009).
To average the total precipitable water observed
by the GPSs, its correlation coe‰cients with precipitation lagged by 24 h in China in January and
February 2008 are shown in Fig. 3. It can be seen
that more water vapor over the Tibetan Plateau
corresponding to more precipitation lagged by 24 h
in the belt area stretching from lower reaches of
Yangtze River valley to the southwestern China
(Xu 2009). The monitored water vapor over the
Tibetan Plateau shows a strong precursor signal of
the heavy snowstorms occurred in Southeast China.
By utilizing the WRF-3DVAR system (Barker et
al. 2004), Peng et al. (2009) made 48 h sensitivity
forecast experiments for precipitation in January
2008 to test the role of the moisture, temperature
and pressure observed by AWSs in the JICA/Tibet
Project in improving the forecast of the snowstorms. As shown in Fig. 4, much weaker southeastern and much stronger southwestern centers of
July 2012
R. ZHANG et al.
9
Fig. 4. 48 h forecast experiments initiated at 0000 UTC 25 January 2008 for accumulated 24 h precipitation
ending at 0000 UTC January 27 2008. (a) is observation; (b)–(d) are control run without data assimilation, data assimilation experiment with only one-cycle 3DVAR applying initial time, and data assimilation
experiment with multi-cycle 3DVAR applying every hour from 1800 UTC 24 August to 0000 UTC 25
January 2008, respectively. (unit: mm) (from Peng et al. 2009)
the 24 h accumulated precipitation than observations (Fig. 4a) can be found in control run without
data assimilation (CNTR, Fig. 4b). In the data assimilation experiment with only one-cycle 3DVAR
applying at initial time (DA-1, Fig. 4c), the southeastern center is less than 35 mm, which enhances
to over 45 mm in the experiment with multi-cycle
3DVAR applying every hour (DA-2, Fig. 4d); the
southwestern center reduces from over 45 mm in
CNTR to less than 45 mm in DA-2. Meanwhile,
the false center around 28.5 N, 108 E in both
CNTR and DA-1 disappears in DA-2. Therefore,
the results of DA-2 are much closer to the observations.
The numerical experiments show that levels of
forecasts have been noticeably raised when the
data collected from observations are assimilated.
The data assimilation techniques in NWP models
and associated automated operational NWP system
developed by utilizing real-time observational data
over the Tibetan Plateau have found applications in
operational forecasts, and applied in the operational
platform. The JICA/Tibet Project has led to the establishment of the operational platform for warning
and predicting severe weathers in East China.
4.3 Land surface processes
The latent and sensible heat fluxes observed by
the PBL tower at Linzhi in 2008 are shown in
Fig. 5. We can see that the surface energy exchange
is dominated by latent heat from mid-March to
October in the rainy season, with averaged latent
heat about 51 W m2 and sensible heat 23 W m2
from 11 March to 10 October. In the dry season
from October to early March, sensible heat dominated the energy exchange with averaged sensible
heat 27 W m2 and latent heat 16 W m2 from 11
October to 10 March. Yearly cumulated latent heat
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Vol. 90C
Fig. 5. Latent (upper panel) and sensible (lower panel) heat fluxes in 2008 observed by the PBL tower at
Linzhi (29.46 N, 94.44 E) (unit: W m2 )
Fig. 6. Mean bias errors of the original and revised Noah model for the surface temperature (Tg ) (left), surface energy budget (Rnet ) (middle) and sensible heat flux (H ) (right) at three arid sites of Shiquanhe
(32 30 0 N, 80 05 0 E) and Gaize (32 18 0 N, 84 03 0 E) in Xizang Autonomous Region, Audubon (31 35 0 N,
110 31 0 W) in Arizona of USA and one semi-arid site of Tongyu_G (44 25 0 N, 122 52 0 E) in Jilin Province
during the daytime (0900–1600 LT), calculated from 30-minute observations and simulations. Sensible heat
flux was not observed at Shiquanhe and Gaize sites.
is 1:07 10 9 J m2 , which is higher than yearly
cumulated sensible heat (7:13 10 8 J m2 ).
The in situ observations were used to evaluate
the revised Noah land surface model (LSM) (Yang
et al. 2002) with an appropriate parameterization of
the thermal roughness length (Chen et al. 2010a).
Figure 6 shows that at the two Plateau sites (Shiquanhe and Gaize), the daytime surface tempera-
ture (Tg ) is underestimated by 10 K on average in
the original Noah model while they are much better
simulated in the revised one. At the two lowland
sites (Audubon and Tongyu-G), the daytime Tg is
also simulated better in the revised one. The mean
bias errors in modeling surface energy budget and
sensible heat flux are simultaneously reduced in the
revised model. The similar improvements to SiB2
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R. ZHANG et al.
11
(Sellers et al. 1996) were also demonstrated (Yang
et al. 2009).
The in situ observed micrometeorological data
at Wenjiang in the period between January and
March, 2008 were used to drive the Land Data Assimilation System developed at the University of
Tokyo (LDASUT) (Yang et al. 2007). The consistency between LDASUT simulations and observations validates the capability of the LDASUT in
reproducing accurate land surface energy budget
(Lu et al. 2009).
Boussetta et al. (2007) developed a coupled landatmosphere satellite data assimilation system as a
new physical downscaling approach, by coupling
the Advanced Regional Prediction System (ARPS)
with the LDASUT. The ARPS produces forcing
data for the LDASUT, and the LDASUT produces
better initial surface conditions for the modelling
system. This coupled system can take into account
land surface heterogeneities through assimilating
satellite data for a better precipitation prediction.
The results of the system application to the Tibetan
Plateau show significant improvement of simulation and prediction of soil moisture and rainfall at
a meso-scale compared with a no assimilation regional atmospheric model simply nested from the
global model.
4.4 Weather and climate over the Tibetan Plateau
The generation processes of mesoscale convective
systems (MCSs), which often cause heavy rainfall
over the Sichuan Basin in China were investigated
by using the JICA/Tibet intensive radio sonde observation data held in the 2008 monsoon season,
the METEOSAT geostational satellite images and
the numerical simulations using a weather research
and forecast (WRF) model (Ueno et al. 2011). The
MCS was generated under synoptic conditions of
merging southwesterly low-level monsoon flows
with a northerly midlatitude air mass following the
trough in the leeward of the Tibetan Plateau. It
was triggered in the evening by strengthening of
the low-level wind convergences with horizontal
shear between the southerly monsoon flow, with
large convective available potential energy, and the
northerly dry intrusion. A sudden increase in the
northerly dry winds was confirmed by the sonde
observation data in the western basin, and was related with the diurnal cycle of cloud activity over
the Qinling Mountains. This study suggests the
MCSs associated with heavy rainfall is caused and
developed by the interaction between a synoptic
Fig. 7. Scatter plots of hourly GPS water
vapor anomalies (DPW, unit: mm) (a)
against hourly rainfall frequency anomalies
(DF, unit: %) and (b) against hourly rainfall amount anomalies (DP, unit: mm) for
their diurnal cycles in summer (June–
August) of 2006–2008 at Lhasa. (from
Liang et al. 2010)
scale atmospheric circulation pattern and the characteristic topography of the Sichuan Basin where
the dry intrusion at the bottom is captured.
Using the water vapor observed by GPS at
Lhasa, the relationship of diurnal cycles between
water vapor and precipitation is shown in Fig. 7
(Liang et al. 2010). It can be seen that the GPS
water vapor is well positively correlated to both
rainfall frequency and amount, with correlation coe‰cients being around 0.92. The peak of the diurnal cycle of GPS water vapor appears at around
1600 UTC, about 2 hours earlier than those of
rainfall frequency and amount appeared, indicating a significant e¤ect of the atmospheric water
vapor on the rainfall frequency and amount. Using
12
Journal of the Meteorological Society of Japan
Fig. 8. Time-longitude section of the vertical
integrated atmospheric heat source (hQ1 i)
(shadings, unit: wm2 ) and 500 hPa vertical vorticity averaged between 30 N and
33 N (isolines, unit: 105 s1 ) for a vortex
over the Tibetan Plateau in the period
from 0600 UTC 25 June 2008 to 0000
UTC 26 June 2008. (from Li et al. 2011)
CloudSat/CALIPSO data, Luo et al. (2011) found
that deep convection in summer (June–August)
over the Tibetan Plateau is lower in cloud top
height, less frequent and smaller in size than those
over the southern slope of the Plateau and the
southern Asian monsoon region. There is more
deep convection at the daytime (i.e., early afternoon) than the nighttime (i.e., soon after midnight)
over the Plateau. Over the southern slope of the
Plateau there is more deep convection occurring
during the nighttime, and over East Asia region
the daytime and nighttime occurrences are about
equal. The convective systems over the Plateau
have much larger size in the nighttime than those
in the daytime.
The evolution mechanism of a vortex over the
Tibetan Plateau in June 2008 was diagnosed (Li
et al. 2011). From Fig. 8, we can see that the vertical integrated atmospheric heat source (hQ1 i) and
the vorticity at 500 hPa moved eastwards with
the center of the hQ1 i to the east of the vorticity
center. The diagnosing the potential vorticity (PV)
equation illustrates that the prominent factor which
attributed to the eastward movement of the vortex
is the vertical uneven distribution of the latent heating through producing positive PV tendencies to
the east of the vortex center, revealing the dynami-
Vol. 90C
cal role of the latent heat in the eastward movement
of the vortex over the Tibetan Plateau.
Based on the tropopause daily observation data
at 14 sounding stations in 1979–2008, Zhou et al.
(2010) found the annual mean heights of the tropical and polar tropopauses over the Tibetan Plateau
are about 17.45 km and 10.08 km, respectively.
The occurrence of the tropical tropopause is dominant in the warm season from May to October and
the occurrence frequencies of the two types of tropopauses are roughly equal in other months. By
using the radiosonde data collected in the three
intensive observation periods in 2008, Chen et al.
(2010b) found in IOP1 the overall bimodal tropopauses near the heights of 10 km and 17 km, respectively, and in both IOP2 and IOP3 a single tropopause near 17 km, which are in consistency with
the statistics by Zhou et al. (2010). The bimodal
tropopauses indicate frequent intrusions of the air
from the troposphere to the stratosphere in the
spring time over the Plateau, providing the evidence of strong stratosphere and troposphere exchange over the Tibetan Plateau.
Taniguchi and Koike (2008) investigated seasonal
variations in cloud activity observed by geostational satellites, an total precipitable water (TPW)
by the Atmospheric Infrared Sounder (AIRS)
aboard Aqua, and atmospheric instability (dq/dp)
derived from Japanese 25-year Reanalysis Project
(JRA-25), around (92.0 E, 31.5 N) over the eastern
Tibetan Plateau. They identified an apparent seasonal progression comprising a first phase of frequent cloud activity (ACTIVE-I), a resting phase
(REST), and a second phase of frequent cloud
activity (ACTIVE-II). Tamura et al. (2010) found
that the temperature in the upper troposphere over
the Tibetan Plateau continues to increase even in
the ‘‘REST’’, and suggested dual atmospheric heating around the Tibetan Plateau during the onset
phase of the Asian Summer Monsoon from late
April to mid June on the basis of the heat budget
analysis and numerical experiment. They showed
that adiabatic warming plays an important role in
warming the upper troposphere downward from
the tropopause, while at the same time, surface
heating warms upward from the land surface of
the Tibetan Plateau.
4.5 Linkage of the Tibetan Plateau with East
Asian and global climates
By examine the correlation between the normalized di¤erence vegetation index (NDVI) over the
July 2012
R. ZHANG et al.
13
Fig. 9. Time series of the leading EOF mode for normalized rainfall in China (gray bars), normalized NDVI
in the southern Tibetan Plateau (24 N–33 N, 75 E–105 E; black bars), and normalized rainfall in southeastern China (south of 27 N, east of 105 E; solid line) and in the area from the middle and lower reaches
of Yangtze River valley to the Yellow River valley (30 N–35 N, 105 E–120 E; dashed line) in summer
(June–August). (from Zuo et al. 2011)
Tibetan Plateau and the leading mode of the empirical orthogonal function (EOF) for the normalized
summer (June–August) rainfall over China, Zuo
et al. (2011) found they are significantly correlated.
As shown in Fig. 9, the time series of the leading
EOF mode agrees well with the NDVI averaged
over the southeastern Tibetan Plateau, which is
positively correlated with the summer rainfall in
the southeastern China and negatively with that
in the area from the middle and lower reaches of
Yangtze River valley to the Yellow River valley.
In the interannual time scale, more vegetation over
the southeastern Tibetan Plateau corresponds to
more precipitation in the southeastern China and
less precipitation in the area from the middle and
lower reaches of Yangtze River valley to the Yellow River valley.
By utilizing the radiosonde data from 12 meteorological stations with an averaged elevation of
3,560 m over the Tibetan Plateau and 16 stations
in the same latitudes in the non-plateau region
with the elevation below 300 m within the area to
the east of 110 E in East China, Zhang and Zhou
(2009) found that over the Plateau there appears
not only a larger temperature drop in the lower
stratosphere and upper troposphere, but also a
larger temperature rise in the lower and middle
troposphere, compared with the non-plateau region
in East China. The larger ozone depletion over the
Plateau may possibly make a major cause allowing
the air temperature change over the Plateau di¤erent from that over the non-plateau region in East
China (Zhou and Zhang 2005; Zhang and Zhou
2009).
The role of the elevated high land of the Tibetan
Plateau in the global water cycle was investigated
by Xu et al. (2008b). As seen from Fig. 10, in
summer (June–August) the Tibetan Plateau exerts
e¤ect on the general circulations in the global
scale. The thermal and mechanical forcings of the
Tibetan Plateau drive ascending motions over the
Plateau and the circulations can cross south-north
and east-west hemispheres respectively. The crossing hemispheric circulations driven by the thermal
and mechanical forcings of the Tibetan Plateau
play an important role in the water vapor transports not only over East Asia, but also in the global
scale.
5. Concluding remarks
To understand a range of key scientific issues,
including the characteristics of atmospheric variations, water vapor transport, hydrologic cycle, and
land-air interactions across the Tibetan Plateau
and its adjacent areas, and to understand their impacts on the floods occurred in the East Asia region
so as to raise the NWP model skill, Chinese and
Japanese scientists jointly conducted an integrated
atmosphere watch with emphasizing of the water
vapor observation across the Tibetan Plateau and
its adjacent areas during the period of 2005–2009
under the JICA/Tibet Project. The project was designed to establish a three-dimensional atmospheric
observing network across the Tibetan Plateau and
14
Journal of the Meteorological Society of Japan
Fig. 10. Climatological wind vectors and
speeds (shadings, unit: ms1 ) for the summer (June–August) averaged in 1948–2006
(a) in the meridional vertical cross section
along 80 E–110 E and (b) in the latitudinal vertical cross section along 27.5 N–
35 N. (from Xu et al. 2008b)
its neighborhood in the east, in an attempt to
collect the needed meteorological data on a long
term basis and to alleviate the impacts caused by
meteorological disasters in the East Asia region, including China and Japan. The project has established an integrated observing platform in this
region, raised analyzing capabilities by utilizing
observational data from both satellite remote sensing and surface based observations, developed NWP
techniques by assimilating observed data into NWP
model to predict severe weathers across the Plateau
and Yangtze River valley, and improved the operational severe weather/climate monitoring, prediction, and assessment systems. The AWSs and GPS
water vapor observing stations established by the
JICA/Tibet Project have become part of the operational system run by CMA. The PBL boundary
layer flux observation systems and wind profilers
from the JICA/Tibet Project have been included as
Vol. 90C
part of CMA’s pilot stations. The establishment of
the plateau-wide observing system is also practically important to the design and implementation
of a range of major Chinese national projects, including the west development campaign, QinghaiXizang railway, south-to-north water diversion,
and flood disaster prevention/control across the
Yangtze River valley. It is also extremely important
for regulating the water resources of the Yangtze
River, making flood forecasts, enhancing the capacity building of major meteorological operations in
the west part of the country, and improving meteorological authorities’ disaster prevention and reduction capability.
Before the JICA/Tibet Project, China launched
two Tibetan Plateau related scientific experiments
in 1979 and 1997 respectively, mainly aiming at
studying the large scale variation of the heat source
across the Plateau and its ties with large scale atmospheric circulations, and land-air interactions in the
Tibetan Plateau (Xu and Chen 2006). The second
experiment conducted in 1997, named as TIPEX,
was jointly implemented with the participation of
both Chinese and Japanese scientists. The integrated atmospheric observing system of the JICA/
Tibet Project conducted this time has exceeded the
previous two experiments in terms of the scope covered, the items observed, technical means applied,
and instrument employed. It has collected much
more data, GPS water vapor data in particular,
in a systematic and reliable manner. Meanwhile,
the JICA/Tibet Project pays close attention to the
meteorological operations, focused more on the
application of observational data and research
achievements in operations, closely in line with constructions of meteorological operations for observation and prediction, and with the national needs
for disaster prevention and reduction. Therefore,
the JICA/Tibet Project has won the support and
active participation of CMA and its operational
departments concerned, which made the project a
success in processes from the establishment of the
project to the implementation, then to the construction, and further to the application of research
achievements. The project makes a good example
for the combined e¤orts of both research and operation. As it was pointed out in the final assessment
report issued by the Japanese authorities in 2009
that the project is implemented not merely for the
project’s sake, and the achievements derived from
the project have been utilized to the full. The
project has rendered an important contribution to
July 2012
R. ZHANG et al.
the studies and operations of the Tibetan Plateau
meteorology.
Acknowledgments
The authors would like to thank the constructive
comments from Dr. K. Ueno and three anonymous
reviewers, Dr. Shengjun Zhang and Ms. Tao Hua
for their help in figure drawing. This work was
supported by the National Natural Science Foundation of China under Grants 40921003 and
40825015, the JICA/Tibet Project of ‘‘ChinaJapanese Center of the Cooperative Research
on Meteorological Disaster’’, the International
Sci-Tech Cooperative Project (2009DFB20540,
2007DFB20210), the special scientific research
project of China commonweal trade (meteorology) (GYHY201006009, GYHY201006053) and
the Independent Research Project of LaSW
(2009LASWZF02). Dr. Kun Yang was supported
by the ‘‘100-Talent’’ Program of Chinese Academy
of Sciences. Audubon Research Ranch data were
obtained through AmeriFlux network.
References
Barker, D. M., W. Huang, Y. R. Guo, A. J. Bourgeois,
and Q. Xiao, 2004: A three-dimensional variational data assimilation system for MM5: Implementation and initial results. Mon. Wea. Rev.,
132, 897–914.
Boussetta, S., T. Koike, T. Graf, K. Yang, and M. Pathmathevan, 2007: Development of a coupled landatmosphere satellite data assimilation system for
Improved local atmospheric simulations. Remote
Sensing of Environment, DOI 10.1016/j.rse.2007
.06.002.
Chen, L., W. Li, and P. Zhao, 2001: Impact of winter
thermal condition of the Tibetan Plateau on zonal
wind anomaly over equatorial Pacific. Sci. China
(Ser. D), 44 (Supplement), 400–409.
Chen, Y.-Y., K. Yang, D.-G. Zhou, J. Qin, and X.-F.
Guo, 2010a: Improving Noah land surface model
in arid regions with an appropriate parameterization of the thermal roughness length. Journal of
Hydrometeor., 11, 995–1006.
Chen, X., Y. Ma, H. Kelder, Z. Su, and K. Yang, 2010b:
On the behavior of the tropopause folding
events over the Tibetan Plateau. Atmos. Chem.
Phys. Discuss., 10, 22993–23016, doi:10.5194/
acpd-10-22993-2010.
China Meteorological Administration, 2007: Atlas of
China Disastrous Weather and Climate (1961–
2006). China Meteorological Press, Beijing, 110
pp. (in Chinese)
15
Fujinami, H., and T. Yasunari, 2001: The seasonal and
intraseasonal variability of diurnal cloud activity
over the Tibetan Plateau. J. Meteor. Soc. Japan,
79, 1207–1227.
Huang, R., 1985: The influence of the heat source anomaly over Tibetan Plateau on the northern hemisphere circulation anomalies. Acta Meteor. Sinica,
43, 208–220. (in Chinese)
Koike, T., 2004: The coordinated enhanced observing
period: An initial step for integrated global water
cycle observation. WMO Bull., 53, 115–121.
Li, L., R. Zhang, and M. Wen, 2011: Diagnostic analysis
of the evolution mechanism for a vortex over the
Tibetan Plateau in June 2008. Adv. Atmos. Sci.,
28, 797–808.
Liang, H., J. Liu, R. Zhang, Y. Cao, and W. Li, 2010:
Diurnal variations of atmospheric water vapor in
Lhasa river valley. Adv. Water Sci., 21, 335–342.
(in Chinese)
Lu, H., T. Koike, K. Yang, X. Xu, X. Li, H. Tsutsui, Y.
Li, X. Zhao, and K. Tamagawa, 2009: Simulating
surface energy flux and soil moisture at the Wenjiang PBL site using the land data assimilation
system of the University of Tokyo. Annual Journal
of Hydraulic Engineering, JSCE, 53, 1–6.
Luo, Y., R. Zhang, W. Qian, Z. Luo, and X. Hu, 2011:
Inter-comparison of deep convection over the Tibetan Plateau-Asian Monsoon Region and subtropical North America in boreal summer using
CloudSat/CALIPSO data. J. Climate, 24, 2164–
2177.
Sellers, P. J., D. A. Randall, G. J. Collatz, J. A. Berry, C.
B. Field, D. A. Dazlich, C. Zhang, G. D. Collelo,
and L. Bounoua, 1996: A revised land surface parameterization (SiB2) for atmospheric GCMs. Part
I: Model formulation. J. Climate, 9, 676–705.
Peng, S., X. Xu, X. Shi, D. Wang, Y. Zhu, and J. Pu,
2009: The early-warning e¤ects of assimilation of
the observations over the large-scale slope of the
‘‘World Roof ’’ on its downstream weather forecasting. Chin. Sci. Bull., 54, 706–710.
Shapiro, M. A., and A. J. Thorpe, 2004: THORPEX: A
global atmospheric research program for the beginning of the 21 st century. WMO Bull., 53, 222–226.
Tamura, T., K. Taniguchi, and T. Koike, 2010: Mechanism of upper tropospheric warming around the
Tibetan Plateau at the onset phase of the Asian
summer monsoon. J. Geophys. Res., 115, D02106,
doi:10.1029/2008JD011678.
Taniguchi, K., and T. Koike, 2007: Increasing atmospheric temperature in the upper troposphere and
cumulus convection over the eastern part of the Tibetan Plateau in the pre-monsoon season in 2004.
J. Meteor. Soc. Japan, 85, 271–294.
Taniguchi, K., and T. Koike, 2008: Seasonal variation of
cloud activity and atmospheric profiles over the
16
Journal of the Meteorological Society of Japan
eastern part of the Tibetan Plateau. J. Geophys.
Res., 113, D10104, doi:10.1029/2007JD009321.
Tao, S., and Y. Ding, 1981: Observational evidence of
the influence of the Qinghai-Xizang (Tibet) Plateau
on the occurrence of heavy rain and severe convective storms in China. Bull. Amer. Meteor. Soc., 62,
23–30.
Ueda, H., H. Kamahori, and N. Yamazaki, 2003: Seasonal contrasting features of heat and moisture
budgets between the eastern and western Tibetan
Plateau during the GAME. J. Climate, 16, 2309–
2324.
Ueno, K., S. Sugimoto, T. Koike, H. Tsutsui, and X. Xu,
2011: Generation processes of mesoscale convective systems following midlatitude troughs around
the Sichuan Basin. J. Geophys. Res., 116, D02104,
doi:10.1029/2009JD013780.
Wen, M., S. Yang, A. Kumar, and P. Zhang, 2009: An
analysis of the large-scale climate anomalies associated with the snowstorms a¤ecting China in January 2008. Mon. Wea. Rev., 137, 1111–1131.
Weng, Y., and X. Xu, 1999: Numerical simulation over
the Tibetan Plateau by using variational technique
revised TOVS Data. Chin. J. Atmos. Sci., 23, 703–
712. (in Chinese)
Wu, G., W. Li, H. Guo, H. Liu, J. Xue, and Z. Wang,
1997: Tibetan Plateau sensible heat pump and
Asia summer monsoon. In: Memorial Corpus for
Zhao Jiuzhang (Ye Duzheng ed.), Scientific Press,
Beijing, 116–126. (in Chinese)
Xu, X., S. Tao, J. Wang, L. Chen, L. Zhou, and X.
Wang, 2002: The relationship between water vapor
transport features of Tibetan-monsoon ‘large triangle’ a¤ecting region and drought-flood abnormality of China. Acta Meteor. Sinica, 60, 257–266.
(in Chinese)
Xu, X., and L. Chen, 2006: Advances of the study on Tibetan Plateau experiment of atmospheric sciences.
J Applied Meteor. Sci., 17, 756–772. (in Chinese)
Xu, X., R. Zhang, T. Koike, C. Lu, X. Shi, S. Zhang, L.
Bian, X. Cheng, P. Li, and G. Ding, 2008a: A new
integrated observational system over the Tibetan
Plateau. Bull. Amer. Meteor. Soc., 89, 1492–1496.
Xu, X., C. Lu, X. Shi, and S. Gao, 2008b: World water
tower: An atmospheric perspective. Geophys. Res.
Lett., 35, L20815, doi:10.1029/2008GL035867.
Xu, X., 2009: The e¤ects of sensitive region over Tibetan
Plateau on disastrous weather and climate and its
monitoring. Engineering Sci., 11(10), 96–107. (in
Chinese)
Vol. 90C
Yanai, M., C. Li, and Z. Song, 1992: Seasonal heating of
the Tibetan Plateau and its e¤ect on the evolution
of the Asian summer monsoon. J. Meteor. Soc. Japan, 70, 319–351.
Yang, K., T. Koike, H. Fujii, K. Tamagawa, and N.
Hirose, 2002: Improvement of surface flux parameterizations with a turbulence-related length.
Quart. J. Roy. Meteor. Soc., 128, 2073–2087.
Yang, K., T. Watanabe, T. Koike, X. Li, H. Fujii, K.
Tamagawa, Y. Ma, and H. Ishikawa, 2007: Autocalibration system developed to assimilate AMSRE data into a land surface model for estimating soil
Moisture and the surface energy budget. J. Meteor.
Soc. Japan, 85A, 229–242.
Yang, K., Y.-Y. Chen, and J. Qin, 2009: Some practical notes on the land surface modeling in the Tibetan Plateau. Hydrol. Earth Syst. Sci., 13, 687–
701.
Ye, D., S. Luo, and B. Zhu, 1957: On the heat balance
and circulation structure in the troposphere over
the Tibetan Plateau and its vicinity. Acta Meteor.
Sinica, 28, 108–121. (in Chinese)
Ye, D., and Y. Gao, 1979: Tibetan Plateau Meteorology.
Scientific Press, Beijing, 316 pp. (in Chinese)
Ye, D., and G. Wu, 1998: The role of the heat source
of the Tibetan Plateau in the general circulation.
Meteor. Atmos. Phys., 67, 181–191.
Zhang, R., and X. Xu, 2008: Climate Observing System
in China. Meteorological Press, Beijing, 291 pp.
(in Chinese)
Zhang, R., 2006: Climate observing system and related
crucial issues. J Applied Meteor. Sci., 17, 705–710.
(in Chinese)
Zhang, R., and S. Zhou, 2009: Air temperature changes
over the Tibetan Plateau and other regions in the
same latitudes and the role of ozone depletion.
Acta Meteor. Sinica, 23, 290–299.
Zhou, S., and R. Zhang, 2005: Decadal variations of
temperature and geopotential height over the
Tibetan Plateau and their relations with Tibet
ozone depletion. Geophys. Res. Lett., 32, L18705,
doi:10.1029/2005GL023496.
Zhou, S., S. Yang, R. Zhang, and Z. Ma, 2010: Seasonal
variation of two types of tropopause height over
the Tibetan Plateau. Trans. Atmos. Sci., 33, 307–
314. (in Chinese)
Zuo, Z., R. Zhang, and P. Zhao, 2011: The relation between vegetation over the Tibetan Plateau and
rainfall in China during the boreal summer. Clim.
Dyn., 36, 1207–1219.