黄河中下游地区夏季逐候降水量的低频振荡特征

本文使用主分量分析黄河中下游地区(河南省)68站1982—1987年夏季(6—8月)逐侯降水量的主要时空特征,并用非整波技术分析所提取的第一主要分量频谱分布的低频振荡特点.分析结果表明该地区降水主要低频振荡周期为6—12候(30—60天)月际振荡及季问振荡15—24候(75—120天).它们年际变化有准两年振荡,其中月际低频振荡与赤道地区的纬向风准两年周期振荡有同相关系.

The Representations of the Low-frequency Fluctuation for the Pentad Precipitation in Summer in the Middle- lower Reaches of the Yellow River Valley

The dominant pattern of the pentad precipitation in summer (June - August) during 1982- 1987 over 68 stations in the middle-lower reaches of the Yellow River valley (Henan Province) is extracted by means of principal component analysis. The characteristics of low-frequency fluctuation are analyzed by non-integer technique of power spectrum. The results show that the predominant period bands represented in the low-frequency fluctuption field are interseasonal fluctuations of 6- 12 pentads (30- 60 days) and intraseasonal fluctuations of 15- 24 pentads (75- 120 days). The annual variation of the low-frequency fluctuations has a pattern of quasi-biannual oscillation of the intensities. Especially, the intensities of the interseasonal fluctuations are in-phase with the quasi-biannial oscillation of the zonal winds in the equatorial area.