Characteristics of Extreme Summer Precipitation and Large-Scale Circulation in Shaanxi Province under Global Warming

Abstract

Based on the daily summer precipitation data of 99 national stations in Shaanxi Province and the ERA5 reanalysis data from 1979 to 2021， the temporal and spatial variations of extreme summer precipitation and the corresponding large-scale circulation characteristics in Shaanxi Province were studied， and the water vapor tracking analysis was conducted on the typical regions.The results showed that the extreme summer precipitation in shannxi Province exhibits more in the south and less in the north， with increasing trend in the central part of northern shannxi and the eastern part of Guanzhong.The variation trend of extreme precipitation in northern Shaanxi， Guanzhong and southern Shannxi is 0.36 mm·a-1， 0.35 mm·a-1 and 0.11 mm·a-1 respectively based on REOF analysis.In summer， there are three main paths for water vapor sources that affect Shaanxi Province.The northern branch comes from the high latitude region of Eurasia， the eastern branch comes from inland river basins， and the southern branch comes from the South China Sea and the Bay of Bengal.In addition， the increase of extreme summer precipitation in Shaanxi Province after 2005 was the result of the combined effects of the high， middle， and low-level atmospheric circulation.The enhanced divergence in the high atmosphere is conducive to the upward movement， and the water vapor is more likely to enter the inland due to the westward extension of the west Pacific subtropical high in the middle atmosphere.The anomalous easterly wind in the south side of the Mongolian anticyclone and the anomalous southeast wind in the lower atmosphere are more conducive to the transport of water vapor to the northwest region.

Keywords

• extreme precipitation
• western pacific subtropical high
• water vapor tracking