东亚副热带季风的北进及其低频振荡

THE NORTHWARD ADVANCE AND OSCILLATION OF THE EAST-ASIAN SUMMER MONSOON

本文利用1971—1980年的资料分析发现,夏季与中国东部雨带相联系的东亚季风属于副热带性质,850百帕14℃等露点线可以作为它的活动指标。副热带季风活动与500百帕上副热带长波活动相协调,它们的季节性变化与准40天周期振荡相结合可以引起副热带季风及其相伴雨带的北跳和停滞,而短的周期振荡则可引起它在停滞期内的南北摆动。

It is found from the data for the period of 1971--1980 that the East-Asian summer monsoon associated with the rain band over eastern Chi-na is of subtropical characteristics and the isodrosotherm of 14°C at850 hPa may serve as a criterion for the monsoon activity. Analysisalso suggests that the monsoon coincides in activity with the subtropicallong waves at 500 hPa.The combination of their seasonal variationswith the quasi 40-day oscillation may cause the northward advance andstagnation of the monsoon and the resulting rain band while the short-period oscillation may yield their north-south swing during theirstagnant stage.