中国干湿状况和干湿气候界限变化研究

选取全国616个地面气象台站1975-2004年的地面资料，通过Penman-Monteith公式计算的参考蒸散确定湿润指数（W），按W为0．03、0．2、0．5和1．0把中国分为极干旱、干旱、半干旱、半湿润和湿润5个干湿区，给出了湿润指数的变化趋势和变异状况的地理分布，讨论了湿润指数的年代际变化特征。结果表明：湿润状况显著增加的地区主要为新疆西北部和中国的西南部，干旱化显著的地区主要在青海的东部、甘肃的南部和四川北部；干湿状况变化从中国的东部向西部逐渐增大，中国的西南地区干湿状况最为稳定；20世纪80年代初全国的平均干湿状况发生变化，由干旱趋向湿润，30a来半湿润、湿润地区干湿状况年际变化大，半干旱区和湿润区增多，半湿润区减少。

A Study on Dry/Wet Conditions and Changes of Dry/Wet Climate Boundary in China

Based on the meteorological record of selected 616 weather stations in China during 1975-- 2004, reference evapotranspiration （ET0） was calculated by using the Penman-Monteith equation recom- mended by FAO, and the wetness index was also estimated from precipitation and ET0. According to wetness index values ：0. 03,0. 2,0. 5,1.0 ,China was classified into five climate zones：extreme arid ,arid, semi - arid, semi-humid and humid zones respectively. The geographical distribution as well as time trend and variation of wetness indices in China are given and its inter-annual and decadal variations are discussed in this paper. Results show that significant wetting trend occurred in northwest Xinjiang Dis- trict and southwest China, the significant drying trend was found in east Qinghai Province, south Gansu Province and north Sichuan Province. The variations in wet/dry conditions gradually became greater from eastern China to western China, with the smallest change in southwest China. 1980 was a transitional year from when the climate turned from a drying trend to a wetting one. From the beginning of 1975, decadal changes were evident in that semi-humid and humid regions, semi-arid and humid regions expanded,and semi-humid ones shrank.