Palmer干旱指数、地表湿润指数与降水距平的比较

Comparison of Palmer Drought Severity Index,Percentage of Precipitation Anomaly and Surface Humid Index

利用中国气象局整编的1951年1月～1999年12月中国160站气温、降水月平均资料,计算了我国160站近49年逐月帕尔默干旱指数、地表湿润指数和降水距平百分率。对比研究表明:PDSI指数和地表湿润指数能抓住降水是干旱最重要的决定因素这一特征,并且,能反映出干旱过程具有更大的时空尺度。在实际蒸发较大的地区,PDSI指数比降水距平百分率描述干旱强度更准确。对于华北地区,在20世纪80年代以前,降水偏多,气温偏低,最大潜在蒸发较小,处于相对湿润的时段;80年代以后,降水偏少,加之气温的升高,华北的干旱越来越严重。

The monthly PDSI, surface moisture index and percentage of precipitation anomaly are calculated for the past 49 years with data from 160 stations in China. The result shows that PDSI and surface moisture index can grasp rainfall, a decisive factor of drought. Moreover, they reflect the process of drought on a greater space and time scale. In the region with more actual evaporation, PDSI describes the severity of drought more precisely than percentage of precipitation anomaly. In North China, before the 1980s, the rainfall was more sufficient, the temperature was higher and the potential evaporation was lower. It was a relatively moist period. Since the 1980s, the rainfall has been less sufficient together with higher temperature, the drought in North China has become more and more severe.