中国西北地区持续干期日数时空变化特征

Spatial and Temporal Variation Characteristics of the Consecutive Dry Days in Northwest China

采用1961—2011年111个地面观测站逐日降水量资料,分析了中国西北地区近51 a四季持续干期日数变化趋势。结果表明:近51 a来西北全区春季和冬季持续干期日数都呈明显的下降趋势,冬季的下降幅度达到-1.6 d·(10 a)-1,而夏季和秋季变化趋势不太明显。空间分布上该区大部分地区持续干期日数变化倾向率春季呈减少趋势,变化倾向率在-5.0~5.0d·(10 a)-1之间;夏季不同的区域变化趋势不同;秋季西北西部呈减少趋势,而西北东部则呈增加趋势;冬季除陕西南部的关中平原和秦巴山地外,其他大部分地区呈减少趋势,变化倾向率在-6.0~3.0 d·(10 a)-1之间。持续干期日数年代际变化和空间变化趋势在不同自然区变化趋势也存在差异。

Based on the daily precipitation data of 111 meteorological stations in Northwest China from 1961 to 2011, the variation of consecutive dry days in four seasons was analyzed. The result indicated that consecutive dry days decreased in the last 51 years in winter and spring with a significant rate of-1.6 d ·(10 a)- 1in winter, but not obvious in summer and autumn. During 1961-2011, in most parts of Northwest China, the consecutive dry days in spring decreased significantly, and the tendencies of variation ranged from-5.0 d ·(10 a)-1to 5.0 d ·(10 a)-1, which is different in summer for different areas. A distinct decrease occurred in the western part of Northwest China in autumn, but consecutive dry days increased in the eastern part of Northwest China. A marked decreasing trend in winter displayed in most parts of Northwest China, and that increased in Guanzhong Plain and Qinling-Daba Mountains, with the tendencies of climatic variation ranges from-6.0 d ·(10 a)-1 to 3.0 d·(10 a)-1. The annual trends and spatial variation of consecutive dry days vary for different natural zones.