Determination of Short-term Heavy Precipitation Threshold and Analysis on Temporalspatial Distribution Characteristics in Chamdo,eastn Xizang

Deji Quzong; SuoLang Duoji; Ciren Wangmu; Ciren Quzhen; Chen Jialong; Zhuoyong

doi:10.3969/j.issn.1004-3403.2025.06.004

Abstract：In this paper,the hourly precipitation(≥0.1mm)observation data of 11 national meteorological observa-tion stations during flood season(May-September)in Chamdo from 2016 to 2024 were used to calculate the 1-hour short-term heavy precipitation threshold in Chamdo by traditional ranking method,Z-index conversion method and square root transformation method.The optimal calculation method for short-term heavy precipitation threshold in Chamdowas determined,and the spatialtemporal distribution characteristics of short-term heavy precipitation in Chamdo were analyzed based on this method.The results show that:(1)The traditional ranking method yielded the best result on the calculation of short-term heavy precipitation threshold in Chamdo,with the threshold value at 5.7 mm·h-1.(2)In terms of spatial distribution,short-term heavy precipitation occurred most frequently in the southeast of Chamdo,followed by the north,and least frequently in the southwest,among where,the cumulative heavy precip-itation occurred most frequently in Mangkang,southeast Chamdo,totaling 86 times,with an annual average of 9.5 times,while that occurred least frequently in Basu,central and south Chamdo,totaling 3 times,with an annual av-erage of 0.3 times.(3)From 2016 to 2024,the total number of short-term heavy precipitation occurrence during the flood season reached 484,with the average annual number at 53.8 times,among which,the cumulative frequency reached the highest in 2018,totaling 80 times,with an average of 7.2 times per station,while that reached the low-est in 2021,totaling only 41 times.(4)Short-term heavy precipitation events mainly occurred in July and August,accounting for 57.8%of the whole year,which began to occur since early May,with the frequency increasing rapid-ly from early June,reaching a peak of 68 times in late July,accounting for 40%of its whole month,with its frequen-cy decreasing since late September.(5)The diurnal variation of short-term heavy precipitation events showed a four-peak distribution,mostly occurring from evening(16:00～19:00)to early night(20:00～23:00).An in-depth explora-tion on the spatialtemporal distribution and variation patterns of short-term heavy precipitation in Chamdo will pro-vide key support for itsaccurate forecasting and early warningn in the local area,which is of great significance for improving the quality of related services.