东亚大陆冬季风的低频振荡特征

The Characteristics of Low Frequency Oscillations in Winter Monsoon over the Eastern Asia

本文对东亚大陆冬季风期间的地面气温、气压的数年资料做了３０～６０天的低频波、准双周振荡等分析。结果表明，东亚大陆地区地面气温、气压的０～６０天波和准双周波具有重要的作用，它们多年平均的低频波方差相对贡献分别为５９．２％（气温）和４９．８％（气压）左右。并且伴有显著的年际差异，如华北气温３０～６０天波强的年份其方差相对贡献可达５０．２％，而最弱的年只占１１．９％左右。另外这两种频率振荡强弱还有明显的地区性，３０～６０天波一般华北和长江流域（２８°Ｎ以北）比其南部地区强；冬季风期间，东亚大陆地区的３０～６０波的经向传播主要是由北向南传播的。大多数年份可以传播至东亚大陆的南端，历时约３～６天，但是这种传播在长江流域以北地区表现为更清楚，在长江以南地区，一方面受到了冬季风本身强弱的影响，另方面还受到来自热带地区以致南半球夏季风低频波北传等因素的影响使得经向传播往往变得比较复杂。

The periodic oscillations with different time scales of atmospheric fluctuation in winter monsoon are revealed by using surface temperature (1979～1986) and pressure data(1979～1983) in China. Result shows that the periodic fluctuations are most important.Their averaged relative variance contributions(30～60 day and 10～20 day oscillations) account for 59.2% of the total variance for the temperature and 49.8% for the pressure respectively.However,their interannual variations and difference among different regions exist obviously.The maximum value of the relative variance contribution of the 30～60 day oscillation of temperature reaches 50.2% but its minimum shows only 11.5%.The oscillation features of the pressure variable are also similar.In addition,the variation of intensity for the 30～60 day oscillation seems opposite to the biweekly one.When the 30～60 day oscillation dominates,the biweekly one becomes weaker.The meridional propagation of the 30～60 day oscillation mainly is southward,covering the distance from North China to South China in 3～6 days except for the years in which the 30～60 day oscillations are exceptional weak.However,this kind of the propagation process is more clear in the region to the north of 28°N than in the one to its south.This may be because of that its southward propagation in lower latitudes not only depends on the intensity of the oscillation in itself but also is influenced by the propagation of oscillations from tropics and the Southern Hemisphere.