四川盆地及东部山区暖季降水的日变化特征OACSTPCD

The spatial and temporal characteristics of hourly mean precipitation in warm season(June-September)over Sichuan Basin and the eastern mountains were analyzed by using the fusion precipitation data,which are available on 0.1°×0.1° grids through 1998 to 2018 obtained from the National Meteorological Information Center,and ERA5 hourly reanalysis data.Results show that the precipitation and frequency in the basin have similar diurnal variation characteristics.The precipitation in the basin is mainly concentrated from night to morning.After the high-value precipitation area reaches the eastern mountainous area of the basin,the precipitation and frequency decrease,and there is no obvious eastward transmission characteristics in the eastern mountainous area.From night to morning,a strong downhill wind was formed on the leeward side of the southeast mountain of the basin,which promoted the formation of mass accumulation in the lower layer of the basin.At the same time,the cyclonic vortex,water vapor input and atmospheric instability in the basin are enhanced,resulting in the enhancement of precipitation in the basin.The eastward propagation of high precipitation value area is related to the shift of water vapor flux direction from southeast to south in the southeast of the basin and the eastward expansion of water vapor convergence area in the lower layer of the basin.The peak time of precipitation in the eastern mountainous area of the basin shows a bimodal distribution in the morning and afternoon,and the spatial distribution is disordered,which may be related to triggering local heavy precipitation under complex terrain conditions.The peak time of precipitation frequency shows a single peak distribution in the afternoon,which is mainly affected by the stability of atmospheric stratification,the daily variation of mountain cyclone circulation and mountain plain solenoid circulation.