1948-2003年全球陆地年降水量变化特征

Secular variation of global land annual precipitation for 1948-2003

研究了1948-2003年全球陆地年降水量的长期变化。研究表明,全球陆地降水量在近56年内平均减少为0．43 mm／a。全球陆地降水量的第一经验正交函数(EOF-1)解释了97．9％的总方差, 它的空间分布与全球年降水量的空间平均图非常相似,EOF-1的时间系数表现为明显的负趋势,趋势系数为一0．37,达到0．0l的显著性,表明全球年降水量明显减少了。此外,研究了全球陆地季、月降水场变化的近期特征,计算了全球36个纬度带平均年降水量的长期趋势,指出有12个纬圈的年平均降水量趋势达到0．05的信度的显著性,其中只有1个纬度带(75°N-80°N)是正趋势。

The investigation of secular variation of the global land annual precipitation（GLAP） for 1948 - 2003 suggests that GLAP experiences a decrease of 0.43 mm/a on average. The spatial distribution of the first empirical otthogonal function （EOF-1） for GLAP analysis accounts for 97.9% of the total variance, which shows almost the same pattern as that of the annual mean precipitation averaged for 1948 - 2003, with a similarity coefficient being as high as 0.99. The temporal coefficients of EOF-1 exhibit a remarkably decreasing trend with the trend coefficient being -0.37 and the confidence level being 99 %. Besides, the variations of seasonal and monthly precipitation over global land and their characteristics in recent years are analyzed, and the trend of GLAP for 36 latitude zones is also examined, h is concluded that the trend coefficients of 12 latitude zones are significant at a confidence level of 95 % , while only one latitude zone（75°N- 80°N） out of 12 zones shows a positive trend.