云南雨季逐候降水量的低频振荡特征

Features of Low-Frequency Fluctuation in Rainy Season in Yunnan Province

应用主分量方法分析了云南省84站1991～2000年雨季（5～10月）逐候降水量的主要时空特征,并用非整波技术分析了所提取的第1、第2主分量频谱分布的低频振荡特点,同时分析了低频振荡现象与El Nino（La Nina）事件及云南雨季降水多、少之间的关系.结果表明：①云南地区雨季降水主要低频振荡周期为6候（30天）、10候（50天）的月际振荡和15～17候（75～85天）的季节内振荡;②云南雨季的候降水每年都存在30天振荡周期,30天振荡是云南雨季固有的振荡;③当发生El Nino或La Nina异常气候事件时,云南雨季的候降水存在50天振荡周期;④当云南雨季存在75～85天振荡时,云南主汛期（6～8月）降水距平百分率为正（除2000年为零距平）;当云南雨季不存在75～85天振荡时,云南主汛期降水距平百分率为负.

The main spatial and temporal distribution features of pentad precipitation in rainy season （May to October） from 1991 to 2000 over Yunnan Province （84 stations） are analyzed by means of the principal component analysis method. The features of low-frequency fluctuation are analyzed by the non-integer technique of power spectrum. The relation between low-frequency fluctuation and El Nino （La Nina） and precipitation in rainy reason of Yunnan Province are studied. The results show： ① The predominant period bands represented in the low frequency fluctuation field are interseasonal fluctuations of 6 pentads （30 days） and 10 pentads （50 days） and the intraseasonal fluctuations of 15 to 17 pentads （75 to 85 days）. ② The 30-day fluctuation period is an intrinsic fluctuation of the pentad precipitation in rainy season of Yunnan Province. ③ When El Nino or La Nina happens, there is a 50-day fluctuation period in the pentad precipitation in rainy season of Yunnan.④ While there is a 75 - 85 day fluctuation period in the pentad precipitation in rainy season of Yunnan, the precipitation anomaly percentage in the main flood period （June to August） in Yunnan is positive; on the contrary, while there is no 75 -85 day fluctuation, the precipitation anomaly percentage is negative.