基于游程理论和Copula函数的辽宁省农业气象干旱特征研究

基于辽宁省近30年的气象站点逐月气候数据,计算SPEI-3指数作为农业气象干旱指标,利用游程理论对辽宁省的干旱特征变量进行识别,使用Copula函数同时从站点尺度和区域尺度对辽宁省干旱特征的联合分布和重现期进行了分析。结果表明:Frank-Copula函数对辽宁省农业气象干旱特征变量联合分布特征模拟效果最好;在相同干旱历时和干旱强度的条件下,各站点的联合重现期比单变量重现期小。干旱事件多集中在干旱历时小于4个月,干旱强度小于3的情况下发生;辽宁省不同干旱类型发生概率由高到低的排序为:季内中旱、跨季中旱、月内轻旱、半年以上重旱、月内中旱、季内轻旱。其中在季内中旱、月内轻旱和月内中旱的情况下,辽西地区发生干旱的概率最高;当干旱历时保持一致,随着干旱强度的增加,其最大最小联合重现期有明显增大的趋势;而当干旱强度保持一致,随着干旱历时的增加,不同干旱等级下联合重现期的变化规律不一致。

Research on Agricultural Meteorological Drought in Liaoning Province based on Run Theory and Copula Function

This paper takes Liaoning Province as the research area,uses the monthly climate data of the meteorological stations of nearly 30 years recorded in Liaoning Province to calculate SPEI-3 agricultural meteorological drought index,and identifies drought events in Liaoning Province based on the run theory.Finally,the Copula function was used to analyze the joint distribution and return period of drought events in Liaoning Province at both site scale and regional scale.The results show that: the characteristics of joint distribution of agricultural meteorological drought feature variables in Liaoning Province were analyzed by Frank-Copula function simulation performed best.Under the same drought duration and drought intensity conditions,the joint return period of each site was smaller than the univariate return period.The most frequent drought events were droughts with duration of less than 4 months and intensity of less than 3.The occurrence probability of drought in Liaoning Province was ranked in descending order as follows : mid-season drought,inter-season drought,light month drought,heavy drought more than six months,medium-term drought,and light season drought.With the drought in the season,light drought in the month,and moderate drought in the month,the probability of drought in the western Liaoning was the highest.When the drought duration was consistent,the joint return period increased significantly with the increase of drought intensity.When the drought intensity kept consistent,with the increase of drought duration,the variation rule of joint return period under different drought grades was inconsistent.