过去45年中国干湿气候区域变化特征

利用中国1960-2004年降水、平均气温、风速和相对湿度等资料,分别采用降水指数和干湿分类函数作为干湿区域的划分标准,将中国划分成三个干湿等级的区域:干旱区、半干旱区和湿润区。结果发现无论以哪种指数作为衡量干湿的标准,我国过去45年的干旱总面积,即干旱区面积和半干旱区面积之和,均为扩大趋势,湿润面积则为减小趋势,这种情况在近十年表现得尤为显著。而半干旱区面积在分析时段变化的幅度最大,是干湿变化的敏感区。但两种结果之间也存在不同:降水指数的结果表明干旱区和湿润区的面积减小,半干旱区的面积增大;而干湿分类函数得到的各个干湿区域的面积则表明干旱区的增大,半干旱区和湿润区的减小。从定量的角度讲,干湿分类函数估算的干旱区面积的45年平均值比降水指数估算的干旱区面积的45年平均值约大15%,其估算的半干旱面积的45年平均值比降水指数的结果约小9%,而两者湿润区面积的45年平均值相差约6%。最后给出了仅分析降水指数就能反映干湿状况的地区和必须分析干湿分类函数才能确定干湿状况的区域。

Area change of dry and wet regions in China in the past 45 years

The following experiment is based on the precipitation,air temperature,wind,maximum temperature, minimum temperature,and relative humidity data during 1960-2004 of 533 stations in China.According to the wet/dry classification function and the precipitation index,the climatic regions in China are delineated into three types:the arid region,the semi-arid region and the humid region,and furthermore,the area of each region is cal- culated by the histogram individually.The results reveal that no matter with what kind of precipitation index and wet/dry classification function as the reference standard,the total arid area,namely the sum of the arid area and the semi-arid area,shows the expanding trends in China in the past 45 years,and the case is more obvious in the latest 10 years.During the course of analysis,we find the scope of semi-arid area changed most markedly,and it is the sensitive region of arid/wet change.But the following results of two indexes also have differences:the precipita- tion index shows the decreasing trend in the arid and the humid region,and the increasing trend in the semi-arid region,respectively;the wet/dry classification function shows the increasing trend in the arid region,and the de- creasing trend in the semi-arid and the humid region.Through quantitative analysis,we find the area of arid region evaluated by wet/dry classification function is 15% larger than the result of the precipitation index,and the area of semi-arid and humid regions is individually 9% and 6% smaller than the result of precipitation index.Finally,we draw the conclusion that what regions could be evaluated only through the precipitation index and what regions must be analyzed by the wet/dry classification function to judge the status of arid/wet.