1948—2001年全球大尺度区域 6～8月降水的长期变化

研究了1948-2001年南、北半球及欧亚大陆、非洲大陆、澳洲大陆、北美大陆、南美大陆、南极大陆和中国 7个大尺度区域 6～8月降水的长期趋势变化和年代际变化。结果表明，南、北半球 6～8月的降水都为负趋势，但南半球降水的负趋势在统计上不显著。在54年的时间段内，南半球 6～8月降水的递减速度为 0．12 mm／a，仅为北半球同期降水减幅（0．24 mm／a）的一半。南、北半球 6～8月降水量年代际尺度的振荡都非常明显，但是，南、北半球年代际变化的特征明显不同。目前北半球仍是在少雨时间段，而南半球处在降水量正常或多雨的时间段。分析还表明，非洲大陆 6～ 8月降水的年代际特征最明显，降水的负趋势也最为显著；欧亚大陆 6～8月降水也有着明显的年代际变化与明显的负趋势变化；澳洲大陆 6～8月降水的年际变化明显，年代际变化相对来说要小得多；北美大陆 6～8月降水的年际变化明显，但无明显的趋势变化。此外，分析了大尺度区域 6～ 8月降水之间的相关关系，发现部分区域大尺度降水量之间有明显的联系；分析了中国夏季降水的长期变化，发现中国夏季降水的年代际变化明显，但无明显的趋势变化。

SECULAR VARIATION OF LARGE-SCALE AREAS PRECIPITATION FROM JUNE TO AUGUST IN 1948-2001

The secular trend and interdecadal variation of precipitation from June to August (JJA) in 1948-2001 over the Northern Hemisphere (NH), the Southern Hemisphere (SH), China, Eurasia, Africa, Australia, North America, South America and Antarctica are investigated. The results indicate that the precipitation of the NH and SH has a negative trend. But for the SH, the trend has not passed the statistical significance. In the 54th years, the lapse rate of precipitation during JJA over the SH is 0.12mm/a, just half as much as that over the NH. The interdecadal variations of precipitation during JJA over the NH and SH are both significant, but their features are very different. Now the rainfall over the NH and SH correspond to dry period and normal or wet period respectively. The secular variation of precipitation during JJA over the six large-scale areas is discussed. It suggests that the interdecadal variation and minus-trend of precipitation during JJA over Africa are the most significant. Next comes Eurasia. The interdecadal variation of precipitation over Australia is weak, and its interannual variation is stronger. The interannual variation of precipitation during JJA over North America is apparent while its trend is not marked. In addition, the correlations among six large-scale areas precipitation are analyzed. Study shows that obvious relationships of precipitation exist among some parts of large-scale areas. The secular changes of precipitation in summer over China are explored, and it shows that the interdecadal variation of precipitation is apparent while its trend is not marked.