中国干旱和半干旱带的10年际演变特征

利用Thornthwaite的干湿分类函数，对近100年中国干旱和半干旱区界限的10年际变动特征进行了分析.结果发现：近50年，在东北中部和华北北部，干旱和半干旱边界呈波动式东移，有明显向东扩展的趋势；在华北南部和陕西南部，半干旱边界也呈波动式南扩，其中陕西南部半干旱边界向南扩展的范围最大.近100年，10年际的干旱和半干旱边界也呈波动式摆动且存在向东和向南扩展的趋势，但在华北南部与东北中部两个地区以20世纪20年代前后干旱和半干旱的范围最大、最强.干旱和半干旱分界线的位置变化与区域升温和降水减少密切相关.

Decadal variations of arid and semi-arid boundary in China

Decadal variations of arid and semi-arid boundary in China during last 100 years have been analyzed by using Thornthwaite's method. The results indicate that, during the last 50 years, there is a distinguished periodic variation of arid and semi-arid boundary in their locations in the middle part of northeast China and northern part of central northern China, and an obvious trend moving to east. In south part of Shannxi province and central northern China, the boundaries of arid and semi-arid areas have been moving to the south, and there is also a periodic variation in the locations, the boundary of semi-arid area reaches the largest extent to the south. During the last 100 years, there is a trend of the boundaries moving to the south or east, and in the south part of northern China and the central part of northeast China, the extent and intensity of arid and semi-arid area was the largest and severest in the 1920s. The location variation of arid and semi-arid boundaries is closely related to regional warming and precipitation reduction.