Abstract
Xinjiang is located in an arid and semi-arid climate region in China, but Xinjiang Ili river valley is more humid, with higher precipitation intensity and precipitation, which is closely related to the role of the Tianshan Mountains. In this paper, through the NCRP 1° × 1° reanalysis data and the conventional observation data of the Ili River Valley in Xinjiang, the terrain sensitivity experiment conducted by the WRF model is used to analyze the short-term extreme precipitation event of the Ili River Valley from 18–19 of May 2017, to reveal the influence of Tianshan Mountains on the extreme precipitation event of the Ili River Valley. The results show that: (1) The reduction or removal of the terrain will cause a wide range of wind field changes, weaken the vertical upward movement of the windward slope, and the accumulation of water vapor before the windward slope will also be reduced; a large-scale change of the terrain will also affect the direction of water vapor transportation. These effects together lead to a decrease or increase in regional precipitation. (2) “Fuzzy” (smooth) terrain will affect the precipitation simulated by changing the local vertical movement and water vapor transport, which shows that the WRF model’s accurate description of the terrain structure characteristics of mountainous areas is beneficial to accurately simulate the precipitation process on the windward slope area.
Highlights
The most extreme precipitation events are inseparable from the interaction with terrain [1,2]
Due to the barrier effect of the Tianshan Mountains, a large amount of water vapor from the Mediterranean and Central Asia carried by the mid-latitude westerly wind is trapped in the Ili River Valley, and water vapor is easy to accumulate in the Valley [16,17,18]
The center of heavy precipitation in this precipitation event appeared in the east and south of the Ili River Valley.It is flat and wide in the west of the Ili River Valley, with low precipitation
Summary
The most extreme precipitation events are inseparable from the interaction with terrain [1,2]. Due to the barrier effect of the Tianshan Mountains, a large amount of water vapor from the Mediterranean and Central Asia carried by the mid-latitude westerly wind is trapped in the Ili River Valley, and water vapor is easy to accumulate in the Valley [16,17,18] As a result, it has brought abundant water resources such as precipitation, snow and glaciers, and making the Ili River Valley a relatively humid area alienated from the surrounding areas, such as Central Asia and Northwest China. NCRP FNL(Final) 1◦ × 1◦ global tropospheric analysis and forecast grid sets are provided every 6 h (https://rda.ucar.edu/datasets/ ds083.2/index.html, accessed on 7 June 2021) [26] for synoptic conditions analysis and WRF simulation It is suitable for 32 levels from 1000 hPa to 10 hPa, including temperature, relative humidity, horizontal wind field, vertical movement, sea level pressure and other data
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