Page 80 - 《高原气象》2026年第1期

高 原 气 象 45 卷
76

Interannual Variation of Moisture Sources in the Three-River Source

Region During Rainy Season and Influencing Factors

CHEN Run ， MENG Xianhong ， YANG Xianyu 1
2
1
（1. College of Atmospheric Sciences， Chengdu University of Information Technology / Sichuan Key Laboratory of Plateau Atmosphere
and Environment， Chengdu 610225， Sichuan， China；
2. Northwest Institute of Ecological Environment and Resources， Chinese Academy of Sciences / State Key Laboratory of Cryospheric
Science and Frozen Soil Engineering， Northwest Institute of Eco-Environment and Resources， Chinese Academy of Sciences，
Lanzhou 730000， Gansu， China）

Abstract： The Three-River Source region （TRSR）， located on the Qinghai-Xizang Plateau （QXP）， are the
source regions of Yangtze， Yellow and Lancang River， plays a critical role in water conservation and is re‐
nowned as the “Water Tower of China”. Under the background of global climate change， this region exhibits
characteristics of rising temperatures and increased precipitation. Sufficient moisture supply is a prerequisite for
precipitation， and the transport pathways and the characteristics of moisture sources have profound impacts on
precipitation mechanisms， water resource regulation， and ecosystem stability in the TRSR. Current research pre‐
dominantly employs traditional Eulerian methods for moisture transport analysis， which makes it difficult to ac‐
curately quantify the relative contributions of different source regions. Studies using Lagrangian trajectory mod‐
els often focus on extreme precipitation， lacking long-term analysis. This study used CFSR reanalysis data to
drive the Lagrangian model FLEXPART， conducting long-term forward simulations of 5 million air parcels from
1980 to 2017. Combined with the Water Sip moisture source diagnostic method， the research focused on the
rainy season （May-September） in the TRSR， systematically identifying and analyzing the main moisture trans‐
port pathways， contribution proportions from various source regions， and further exploring their spatiotemporal
variation characteristics and relationships with major large-scale circulation systems. Results indicate that the
main moisture transport channels affecting precipitation in the TRSR during rainy season can be summarized as
two types： one enters from the west or north along the mid-latitude Westerly， characterized by numerous air par‐
cels at higher altitudes but with relatively lower moisture content； the other enters from the south or east along
the Asian monsoon， although the quantity is relatively small， the routes pass through marine areas with low alti‐
tudes and rich moisture content. Moisture sources diagnostics using the Water Sip method reveal that the rainy
season moisture sources for the TRSR exhibit a distribution pattern radiating outward from the QXP， with the
most prominent expansion towards the South Asian monsoon region. The internal moisture cycle of the QXP
plays a dominant role in precipitation in the TRSR during the rainy season， contributing 66. 3% of the moisture.
The South Asian monsoon region ranks second， contributing 18. 87% of moisture， while the Westerly region and
East Asian monsoon region contribute relatively less， at 7. 00% and 3. 08% respectively. From a spatiotemporal
perspective， moisture sources during the rainy season in the TRSR showed an overall increasing trend from 1980
to 2017， with the most significant increases from the QXP and the southern of the Himalayas， exceeding 4 mm·
（10a） . This trend is closely related to the strengthening of the South Asian monsoon and plateau monsoon，
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which enhanced moisture transport capacity from the South Asian monsoon region， the interior and surrounding
areas of the QXP. The moisture contribution from the western QXP to Central Asia showed a declining trend，
mainly affected by the southward shift and weakening intensity of the Central Asian Westerly. Meanwhile， the
trend in the intensity and position of the East Asian monsoon were not significant， resulting in a relatively weak
effect on moisture transport to the TRSR during the rainy season.
Key words： Three-River Source Region； moisture tracking； climate change； FLEXPART