1965-2013年黄土高原地区极端降水事件时空变化特征

基于黄土高原地区52个气象站点1965-2013年逐日降水数据,辅以一元线性趋势分析、相关分析、Mann-Kendall检验及反距离加权插值(IDW)等方法,本文分析了黄土高原地区极端降水事件时空变化特征.结果表明:1)时间上,持续性指标和强度指标中除降水强度(SDⅡ)外均呈现减小的趋势;绝对指标和相对指标中除R10 mm降水日数(R10 mm)外,其他指数均呈现增加的趋势,但均未通过0.05显著性水平检验.2)空间上,就持续性指标来看,连续无雨日数(CDD)增加趋势最大的位于区域Ⅲ,连续降水日数(CWD)和年降水总量(PRCPTOT)在区域Ⅱ的北部的增幅最大;强度指标中,1d最大降水量(RX1 day)和5d最大降水量(RX5 day)在区域Ⅱ的中部和北部增幅最大,SDⅡ增幅最大的地区主要集中在区域工和区域Ⅱ的北部地区;绝对指标中,R10 mm、R20 mm降水日数(R20 mm)和R25 mm降水日数(R25 mm)的趋势变化呈由南向北增加的趋势;相对指标中,异常降水日数(R95p)和极端降水日数(R99p)增幅最大的地区主要集中在区域Ⅱ.3)CDD与经度、纬度呈显著的负相关,年降水总量(PRCPTOT)、R10 mm和R25 mm与纬度呈显著正相关,其他极端降水指数与经纬度和海拔高度的相关性不显著.4)主成分分析的结果表明2类极端降水指数的总贡献率达到80.73％,除CDD外,其他极端降水指数与PRCPTOT均具有良好的相关性,且均通过了0.01显著性水平检验.5)Hurst指数结果表明黄土高原地区CDD、SDⅡ、R10 mm、R20 mm和R25 mm极端降水指数变化均呈反向变化特征,其他极端降水指数呈同向变化特征.

Spatiotemporal variations of extreme precipitation events in the Loess Plateau from 1965 to 2013

Daily precipitation data at 52 meteorological stations were used to analyze spatiotemporal variation in 11 extreme precipitation indicaters in the Loess Plateau from 1965-2013 by linear regression,MannKendall,correlation analysis and inverse distance weighting (IDW).For temporal variation,apart from simple daily intensity index (SD Ⅱ),other sustainability indices and intensity indices were found to exhibit nonsignificant decreasing trend from 1965-2013,absolute indices and relative indices exhibited non-significant increasing trend except heavy precipitation days (R10mm).For spatial variation,consecutive dry days (CDD) increased the most in region Ⅲ,and consecutive wet days (CWD) and wet day precipitation (PRCPTOT) increased the largest in the northern region Ⅱ.Maximum 1-day and 5-day precipitations (RX1day,RX5day) increased the largest in the central and northern region Ⅱ,and the SD Ⅱ increased the largest in northern region Ⅰ and Ⅱ.The change trend of R10mm,very heavy precipitation days (R20mm) and R25mm increased from south to north in the Loess Plateau.Very wet day precipitation (R95p) and extremely wet day precipitation (R99p) increased the largest in northern region Ⅱ.The CDD had negative correlation with longitude and latitude,PRCPTOT,R10mm and R25mm had positive correlation with longitude.Other extreme precipitation had non-significant correlation with longitude,latitude and altitude.Principal component analysis indicated that two types extreme precipitation explained variances was 80.73％.Apart from CDD,other extreme precipitation had significant correlation with PRCPTOT at the level of 0.01.Hurst index indicated that CDD,SD Ⅱ,R10mm,R20mm were reverse characteristics,while PRCPTOT,RX1day,RXSday,R95p and R99p were similar characteristic.