Page 174 - 《高原气象》2025年第3期

高 原 气 象 44 卷
732

Research on the Impact of Mountain-Valley Wind on Topographic

Precipitation in the Ili River Valley Based on GPM Observations

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WANG Zhimin 1， 2， 3 ， FENG Wanyue ， YANG Jing ， LI Yuanyuan ， WANG Hui ， FU Yapeng 2
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（1. Weather Modification Office of Xinjiang Uygur Autonomous Region， Urumqi 830002， Xinjiang， China；
2. Key Laboratory of High Impact Weather （special）， China Meteorological Administrationl， Changsha 410000， Hunan， China；
3. Institute of Desert Meteorology， China Meteorological Administrationl， Urumqi 830002， Xinjiang， China；
4. Meteorological Technology and Equipment Support Center of Xinjiang Uygur Autonomous Region，
Urumqi 830002， Xinjiang， China；
5. Nanjing University of Information Science & Technology， Nanjing 210044， Jiangsu， China；
6. Weather Modification Center of China Meteorological Administration， Beijing 100000， China）

Abstract： Studying the impact of valley winds on terrain precipitation is crucial for gaining a deeper understand‐
ing of the mechanism of precipitation formation under complex terrain conditions. Based on GPM/DPR data from
2014 to 2021， the connected domain method was used to identify the summer terrain precipitation system in the
Ili River Valley. Combined with the 10 m surface wind data from ERA5， the precipitation process was divided in‐
to valley wind type and mountain wind type. The spatiotemporal distribution， vertical structure， and macro and
micro characteristics of precipitation in these two types of "trumpet mouth" terrain were compared and analyzed.
The results show that valley wind precipitation is concentrated on the windward slopes of the southern and east‐
ern foothills of the valley， with the precipitation period mainly from noon to evening （12:00 -20:00 Beijing
time， same as after）. Mountain wind precipitation is more abundant in the valley plain， with more precipitation
occurring from night to morning （01:00 -06:00）. The average wind speed of valley wind （0. 79 m·s ） is 6. 8%
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higher than that of mountain wind （0. 74 m·s ）. The average near surface precipitation rate （R） and rain top
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height （STH） of valley wind and mountain wind precipitation are 1. 32 mm·h ， respectively 1. 15 mm·h ， 5. 90
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km， 5. 72 km， statistics show a positive correlation between STH and R； Under the influence of uphill winds，
the R， STH， mass weighted average diameter （D ）， and particle number concentration （dBN ） of valley wind
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precipitation increase under the influence of terrain uplift， reaching a maximum at an altitude of 2 -3 km. The up‐
welling airflow formed on the windward slope promotes the condensation and coalescence of cloud droplets into
raindrops； The average dBN of valley wind precipitation （33. 5） is nearly 3% smaller than that of mountain
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wind precipitation （34. 5）， while the average Dm of the former （1. 63 mm） is 18. 1% larger than that of the lat‐
ter （1. 38 mm）. Due to the lower radar reflectivity factor of mountain winds compared to valley winds in the liq‐
uid phase region below 0 ℃， when raindrops descend to the dry layer near the ground， the large droplets break
and evaporate， resulting in more dBN and smaller D . Valley winds affect the macroscopic structure and micro‐
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physical processes of terrain precipitation. In future research on identifying the potential of terrain cloud artificial
precipitation enhancement and numerical simulation of fine structure of precipitation in mountainous areas， atten‐
tion should be paid to the role and dynamic mechanism of valley winds.
Key words： Ili River Valley； rain cell； surface wind； GPM/DPR