考虑气候分区的甘肃省干旱时空分布特征分析

Spatial and Temporal Distribution Characteristics of Drought in Gansu Province Considering Climate Zoning

甘肃省地处生态脆弱区,气候条件复杂,干旱发生概率高、范围广。为了更好地研究甘肃省干旱时空变化特征,综合考虑甘肃省气候类型和地理特征将其划分为4个气候分区(Ⅰ区,河西大陆性气候区;Ⅱ区,陇中北部季风气候区;Ⅲ区,陇南-陇中南部季风气候区;Ⅳ区,甘南高寒气候区),并采用甘肃省26个国家气象站点的气象资料,计算其近60年(1960—2019年)的月、季和年尺度的标准化降水蒸散指数(SPEI-1、SPEI-3、SPEI-12),结合气候倾向率、Mann-Kendall突变检验、空间插值等方法探讨甘肃省近60年的干旱时空演变特征。结果表明:从时间变化角度看,不同时间尺度的SPEI均呈减小变化趋势,且随时间尺度的增大,SPEI波动幅度越小;在四季变化上,春、夏、秋季SPEI在甘肃省各气候分区都呈现在波动中下降的趋势,且下降趋势明显,表明干旱趋势显著,冬季SPEI在各气候分区呈现在波动中上升的趋势,表明有湿润化的趋势。从空间变化角度看,甘肃省Ⅰ区呈干旱减缓趋势,Ⅱ区、Ⅲ区和Ⅳ区呈干旱加剧趋势,且春季各气候分区干旱加剧趋势明显,夏、秋季次之,而冬季基本上都呈现干旱减缓趋势;甘肃省不同气候分区不同等级干旱发生频率分布差异大且不均衡,干旱频率由小到大依次为:特旱、中旱、重旱、轻旱。

Gansu Province is located in an ecologically fragile area,with complex climate conditions,high probability and wide range of drought.In order to better study the temporal and spatial variation characteristics of drought in Gansu Province,it was divided into four climate zones according to the climate type and geographical characteristics:the continental climate area of Hexi(Region Ⅰ),the monsoon climate area in the northern of Longzhong(Region Ⅱ),the monsoon climate area of Longnan and the south of Longzhong(Region Ⅲ) and the alpine climate area of Gannan(Region Ⅳ).The meteorological data of 26 national meteorological stations in Gansu Province were used to calculate the standardized precipitation evapotranspiration index on monthly,quarterly and annual scales(SPEI-1,SPEI-3 and SPEI-12)in the past 60 years(1960—2019).The spatiotemporal evolution characteristics of drought in Gansu Province in recent 60 years were discussed by means of climate tendency rate,Mann-Kendall mutation test and spatial interpolation.The results showed that the SPEI values of different time scales showed a decreasing trend from the perspective of time process,and the fluctuation range of SPEI values was smaller as the time scale was increased.For seasonal factor,in spring,summer and autumn,the SPEI values showed a downward trend in fluctuations in all climate regions of Gansu Province.And the downward trend was obvious,indicating a significant drying trend.In winter,the SPEI values showed a rising trend in fluctuations in various climate regions,indicating a trend of wetting.Spatially,it showed a humid trend in Region Ⅰ of Gansu Province,but it was dire in Region Ⅱ,Ⅲ and Ⅳ of Gansu Province.And in spring,the drought in various climate regions of Gansu Province had an obvious trend of aggravation,followed by summer and autumn,while in winter,the drought was basically slowed down.The frequency of occurrence of different levels of drought in different climate regions of Gansu Province was very different and uneven,and the drought frequency from smallest to largest was extreme drought,moderate drought,heavy drought and mild drought.