1948～2003年全球陆地年降水量变化特征

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。

Secular variation of global land annual precipitation for 1948-2003

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 orthogonal 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. It 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.