基于SPEI的1981—2017年中国北方地区干旱时空分布特征

Temporal and spatial characteristics of drought based on SPEI in northern China from 1981 to 2017

基于逐日降水量实测数据以及根据Penman-Monteith公式获取的潜在蒸散发量,计算了中国北方地区1981-2017年的标准化降水蒸散指数(SPEI),并采用Mann-Kendall检验及旋转经验正交矩阵(REOF)等方法,探讨了近37年来北方地区干旱时空分布特征。结果表明:(1)1981-2017年北方地区约有74%的区域SPEI呈减小趋势,其中显著减小( P <0.05)的区域占总面积的43%,区域平均SPEI趋势率为-0.015·a -1 ( P <0.01),1994年为其突变年;(2)近37年来,北方地区轻度干旱(-1.2<SPEI≤-0.5)和中度干旱(-2<SPEI≤-1.2)发生频次呈增加趋势的区域分别占总面积的78%和81%,表明干旱化现象主要表现为轻度和中度干旱;(3)在研究时段内,春季干旱化最严重,冬季最弱;(4)研究区通过REOF方法划分的三个主要干旱特征区分别为华北、东北和西北区,其中华北区无明显趋势变化;东北区经历了干旱化到湿润化的反转;西北干旱区在研究时段内干旱化最为严重。

Based on the measured daily precipitation and calculated the potential evapotranspiration,using Penman-Monteith formula, the standardized precipitation evapotranspiration index (SPEI) from 1981 to 2017 in northern China was established.The Mann-Kendall test (MK)and rotating empirical orthogonal matrix (REOF) method were used to explore the temporal and spatial characteristics ofdrought in this region over 37 years. The results showed that:(1) About 74% of the whole region had decreasing SPEI from 1981 to 2017, and about 43% of area of whole region had a significant decrease trend. The average SPEI trend rate was -0.015·a -1 ( P <0.01). Moreover, the turning point of SPEI change occurred in1994;(2) The area that the frequency of slightly arid (-1.2<SPEI≤-0.5) and moderately arid (-2<SPEI≤-1.2) in northern China increased over 37 years indicating that the aridificationwas slight and moderate;(3) Themost severe aridification was in spring and the least in winter.(4) The northern China can be divided into three arid characteristic zones using REOF: Northern China arid area, northeastern China arid area, and northwestern arid area. There wasno obvious trend change in the northern China arid area. The northeastern China arid area had experienced a reversal of aridification to humidification. The aridification in the northwestern arid area was the most severe.