中文摘要：

利用1982～2001年NOAA-AVHRR旬合成的光谱植被指数和NOAA-AVHRR第4和第5通道亮温计算的陆地表面温度资料,利用水分亏缺指数（WDI）作为干旱评价指标,分析了全国近20 a干旱时空分布特征,并对近20 a来各月份发生干旱的频率进行了分析.提取全国雨量观测站点的水分亏缺指数和20 a干旱发生频次,分析了它们与降水量的关系.研究结果表明：（1）我国地域辽阔,气候类型多样,干旱发生具有明显的时空差异.四川盆地属于冬春旱型;西北为常年干旱型;黄淮海平原为春夏旱型;西南青藏区为常年湿润型;华南为冬春旱型;（2）在年降水量少于500mm时,20 a平均降水量与20a平均水分亏缺指数和20a总干旱发生频次都呈明显线性关系,但在年均降水大于500mm时,水分亏缺指数及干旱发生频次与降水量关系都不显著,表明WDI可以很好地评价干旱胁迫的程度,但并不适宜评价湿润程度.

英文摘要：

Based on the land surface temperature data figured out of the composite data of channel 4 and channel 5 light temperature of NOAA-AVHRR, together with spectrum vegetation indices, water deficit index （WDI） was estimated as the indicator of drought. The spatio-temporal characteristies of droughts and drought occurrence frequency of each month in China in the past two decades （ 1982 - 2001） were analyzed. Results showed that in spring, Northwest China, North China and South China had a higher drought occurrence frequency; from May to August, Northwest China and North China had; and from September to December, Northwest China, North China, Central China and Sichuan basin had. The analysis of relationship between average annul precipitation and average WDI, drought occurrence frequency in the 20 years demonstrated that they were closely related in a linear pattern when the average annul precipitation was less than 500 mm but when the average yearly precipitation was more than 500 micro-metal, WDI was not distinctly related to precipitation and drought level.