云南雨季开始期演变特征分析

Evolution Feature of the Rainy Season Onset Time of Yunnan Province

应用EOF分析方法、小波分析方法及云南16个地州代表站1961～2002年共42年逐日降水量资料,对云南雨季开始期的空间分布、时间演变及多尺度周期变化等特征进行了诊断研究.结果表明：1）云南雨季开始期的空间分布,第一主要特征是全省雨季开始期一致偏早（晚）;第二主要特征为云南滇中及以东、以南地区与云南西部雨季开始期反向变化的空间异常分布型态;2）云南雨季开始期存在明显的40年左右长周期、28年左右的年代际周期和8年左右的年际周期.从小波方差看,云南雨季开始期的变化以40年和28年左右的变化周期的振动最强,变化最显著,而年际变化相对较弱;3）云南雨季开始偏早期与偏晚期5月份500 hPa高度距平场有着明显区别;4）印度季风与南海季风对云南雨季开始爆发也起着积极的作用.

Applying EOF method, Morlet Wavelet Method and 42-year precipitation data of 16 representative stations in Yunnan province daily from 1961 to 2002 to research the spatial distribution, temporal evolution and multiscale period of the rainy season onset time of Yunnan Province. The results indicated that： 1） The firstly main spatial distributive feature of the rainy season onset time in Yunnan was that the whole province＇s rainy season onset time was unanimously earlier （or later） than the normal time; The secondly main spatial distributive feature of the rainy season onset time in Yunnan was that it was reverse spatial distribution between the middle, the eastern and the southern areas of Yunnan and the western areas of Yunnan; 2） There was obviously approximately 40a long oscillation period, approximately 28 a interdeeadal oscillation period and approximately 8 year interannual oscillation period. It could be seen from wavelet variance that the 40-year and 28-year period were the strongest and most remarkablc among the periods of rainy season onset time in Yunnan and interannual change period is relatively weaker; 3） There was an obviously difference of 500 hPa anomalous height field in May between above-normal and belownormal years of rainy season in Yunnan; 4） India monsoon and south sea of China monsoon had positive effect on the rainy season onset time in Yunnan.