基于精细资料的宁夏春季干旱特征分析

Distribution Characteristics of Spring Droughts Based on High-Resolution Data in Ningxia

本文利用多种地面精细观测资料,统计分析得到近55a宁夏春季干旱的精细化空间分布和多时间尺度变化特征。结果表明:在采用了更为精细的观测资料后,宁夏春季干旱的分布显得更为不均,呈中部多发南北少发的分布特征而干旱平均强度却呈中部弱南北强的分布特征;最大春季干旱强度分布呈明显的多极性分布。在宁夏5地市中,吴忠市、银川市、中卫市3市较易发生干旱。宁夏春季干旱发生次数基本呈逐年增加的趋势,但平均强度呈逐年减弱的趋势;年代际发生次数的增加趋势更加明显;在20世纪80年代前后存在1次突变。春季干旱强度具有较为稳定的气候态,3、5月易出现大范围轻旱以上的干旱过程;3月上旬、5月上旬、5月下旬较易出现重旱级别的干旱过程。500hPa大陆高压脊与大气环流的变化是造成西北地区春季干旱强弱分布的主要原因之一。

Based on high-resolution spatial and temporal data over Ningxia from 1961 to 2015,we analyzed the distribution characteristics of spring droughts by statistical methods.The results reveal that there were more droughts in spring happened in the central Ningxia than in the northern or southern parts,but the average intensity of droughts had contrary characteristics.The maximum spring drought intensity demonstrated obviously multi-polar distribution characteristics.There occurred more frequently serious droughts in Wuzhong,Yinchua,and Zhongwei.The frequency of spring droughts in Ningxia increased basically year by year,but the average intensity decreased gradually,while inter-decadal characteristics were more obvious.The spring drought intensity was relatively stable,and large scale droughts occurred more frequently in March and May.During early March,early May and late May,serious drought processes occurred more easily.The main reasons for spring droughts in Northwest China include the variation of the ridge of the continental high and 500 hPa atmospheric circulation.