塔里木盆地不同气候态参照值对极端降水量特征的影响OA

Climate normals serve as the foundation for identifying and assessing extreme precipitation events.However,variations in these baselines can lead to biases in the detection of extreme precipitation events.Address-ing these potential biases is essential for water resource regulation and flood emergency management in arid re-gions.In this study,based on the daily precipitation data from 39 meteorological stations in the Tarim Basin,we divide the 1961-2024 period into 5 climate normal periods:Normal Ⅰ(1961-1990),Normal Ⅱ(1971-2000),Nor-mal Ⅲ(1981-2010),Normal Ⅳ(1991-2020),and Normal Ⅴ(1961-2024).Using the percentile threshold meth-od,linear trend analysis,and range of variability approach(RVA),we comparatively analyze the spatiotemporal variations of heavy precipitation(R95p)and extreme precipitation(R99p)across the five climate normal periods and assess the effects of different climate normals on extreme precipitation detection.The results demonstrate that the choice of climate normal periods substantially affects the assessment of dry/wet conditions in the Tarim Basin.When using Normals Ⅰ and Ⅱ as reference periods,the proportions of years with positive precipitation anomalies are 65％and 53.3％,respectively,and the proportions of years with precipitation classified as"above normal and higher"are 39％and 34.4％,respectively,tending to overestimate"wet"conditions.Conversely,us-ing Normals Ⅲ and Ⅳ as reference periods may overestimate"dry"conditions.The R99p index is considerably more sensitive to threshold changes than the R95p index.Deviations estimated by the RVA across different cli-mate normals range from 0.02 to 0.45,with 20.5％-25.6％of stations exhibiting moderate biases,primarily dis-tributed across plain stations at the northern foothills of the Kunlun Mountains.Therefore,the selection of climate normal periods has a noticeable impact on extreme precipitation detection in these areas.The high-value areas of extreme precipitation are concentrated in the high-altitude mountainous regions of the Central Tianshan Moun-tains.The trends in R95p and R99p are generally consistent,with linear trend rates ranging from-22.9 mm·(10a)-1 to 11.2 mm·(10a)-1 for R95p and from-21.8 mm·(10a)-1 to 6.8 mm·(10a)-1 for R99p.Moreover,within the same climate normal period,increasing and decreasing trends exhibit substantial longitudinal and latitudinal spatial dif-ferences.The increase in extreme precipitation over the basin from 1961 to 2024 is primarily attributable to R95p events.However,the increase in total precipitation is not dominated by extreme precipitation.With increasing contributions from other precipitation grades,regional precipitation stability has been enhanced.This study eluci-dates the effects of different climate normals on extreme precipitation characteristics in the Tarim Basin and high-lights the differential responses of R95p and R99p to climate normal shifts.Our findings provide a scientific refer-ence for the standardization of extreme precipitation detection indexes and the selection of reference periods in ar-id regions.