东亚干旱、半干旱区范围与边界层高度变化的关系分析

Analysis of the relationship between variations of the boundary layer height and ranges of arid and semi-arid regions in East Asia

采用1979-2014年ERA-Interim再分析资料,对东亚干旱、半干旱区边界层高度(BLH)的时空变化特征进行了系统分析,初步探讨了BLH变化在干旱、半干旱区范围变化中的反馈作用.结果表明,BLH整体呈经向扁平分布,以塔克拉玛干沙漠为高值中心,其西部和北部边界层高度变化梯度较大、向东变化则较平缓,干旱、半干旱区的分界线与边界层高度的分布存在较好的一致性.36 a数据分析可知,边界层高度呈增大的趋势,分析年代际尺度变化发现,从20世纪末到21世纪初,边界层高度在高值中心及其北部呈先增后减的趋势,其西部、中部和东部的边界层高度呈减、增、减的年代际变化趋势,干旱、半干旱区分界线也有对应的变化趋势.边界层高度增加,分界线向外扩张;边界层高度减小,分界线向内缩减,干旱、半干旱区的范围也相应地扩大和缩小,进一步表明东亚干旱、半干旱区范围的变化与边界层高度的变化有着较好的对应关系.边界层高度的变化对干旱、半干旱区范围变化存在着反馈作用.边界层高度升高,增加了水分蒸发,使得大气中的水汽含量增多,空气变得湿润,在一定程度上缓解了气候变干的趋势,阻止干旱、半干旱区范围的持续扩大.

To discuss the feedback effect of the variation of boundary layer height（BLH） on the range of arid and semi-arid regions in East Asia,ERA-interim reanalysis data（from 1979 to 2014） were used to capture the characteristics of BLH variations.The study showed that a high BLH climatology center was located at the range of Taklamakan Desert with a sharp decrease toward west and north,and a slow decrease to the east;it also showed a nearly identical pattern of BLH distribution and semiarid region location.The analysis of the 36 years＇ data showed that the BLH was rising.From the end of the 20 th century to the dawn of 21 st century,BLH over the highest value center in the Taklamakan and its northern surrounding region presented a positive trend,and decreased after that.The inter-decadal variation of BLH over the west,central and east of the study area showed a decreasing trend and followed by an increasing and then decreasing trend.The arid and semiarid dividing line showed the same trends.The dividing line of arid and semi-arid regions spread outside with the increase of BLH,and reduced with the decrease of BLH.The location of semiarid and arid regions had a great synchronous response to the spatial distribution of BLH.There existed a feedback effect of BLH variation on the ranges of the arid and semi-arid zones.When BLH increased,the evaporation of water would increase,so as to increase the content of atmospheric water vapor;at the same time the air turned humid which,in turn,alleviated its dry climate trends to some extent and prevented the range of arid and semi-arid regions from expanding.