Extreme Summer Precipitation Characteristics and Associated Water Vapor Transport in Southern Xinjiang

Abstract

In this study, we analyzed the spatial and temporal characteristics of extreme precipitation in summer in southern Xinjiang (SXJ) using CN05.1 daily precipitation data, the National Centers for Environmental Prediction (NCEP) monthly average data, and ERA5 four-times-daily reanalysis data from 1961 to 2020, determined the interdecadal variation in extreme precipitation, and further explored the circulation mechanisms and anomalous water vapor transport characteristics associated with changes in extreme precipitation. The results showed that extreme precipitation, extreme precipitation days, and extreme precipitation contribution in SXJ all increased significantly, with the turnaround occurring in 1986. Enhanced vertical upward motion, greater convergence of water vapor at lower levels, and a more unstable atmospheric convection led to an increase in extreme precipitation along the southern border region. The eastward Pacific Ocean and southward Indian Ocean provided anomalous water vapor transport, and the boundary water vapor flux trend and its correlated distribution with extreme precipitation showed that southern boundary water vapor transport played an important role in the increase in extreme precipitation. At vertical heights, the dominant longitudinal water vapor transport fluxes were concentrated in the middle and upper layers, whereas the latitudinal water vapor transport fluxes were concentrated in the middle and lower layers.