从海平面气压场的波谱分析比较南、北半球大气环流的变化

本文应用沿纬圈的谐波分析,对1951—1960年各年逐月南、北半球海平面气压进行分解,对比两个半球的副热带(30°N,30°S)及中纬度(50°N,50°S)的超长波活动发现:(1)南、北两个半球月平均大气环流都存在有性质不同的两类变化,即季节性变化与非季节性变化。在海陆对比明显的北半球,不论西风带还是副热带季节性变化都比较清楚。而南半球仅副热带季节性变化明显,西风带则是非季节性变化占优势。(2)南、北两个半球大气环流的季节变化,都有明显的年际差异。通常,北半球夏季建立(南半球是夏季结束)的年际差异大,北半球夏季结束(南半球是夏季建立)的年际差别较小。(3)超长波位置的年际变化与海陆分布有密切关系。陆地面积大的地区,占优势的超长波位置比较稳定,在几乎全为海洋的50°S,则超长波无论占优势与否,波槽位置的年际变化都较大。

A COMPARATIVE STUDIES ABOUT GENERAL CIRCULATIONS IN NORTHERN AND SOUTHERN HEMISPHERES IN RELATION TO THE SEA-LEVEL PRESSURE HARMONICS

Zonal harmonic analysis are carried out for monthly sea-level pressure along four latitude belts (30°N, 30°S, 50°N, 50°S) for period from 1951 to 1960. The characteristics of the caculated ultra-long wave show that: (1) there are two kinds of variations of the general circulation, seasonal and un-seasonal. In the Northern Hemisphere, in which the continent-ocean contrast is large, the seasonal variation is significant in both subtropical and temperate belts. In the Southern Hemisphere it is dominant only in the subtropical belt, while in the temperate belt the unseasonal variation is more evident. (2) There are significant interannual variations of the seaaonal course in both Southern and Northern Hemispheres. The beginning of summer in the Northern Hemisphere and the ending of summer in the Southem Hemisphere are changed obviously from one year to another. But the beginning of northern summer has much greater stability and so does the ending of southorn summer. (3) The interannual variation of the positions of ultra-long waves associated closely with the distribution of continent and ocean. The dominant ultralong waves are more stable in the latitude belt in which the continents occupy a great portion of the area. In the 50°S belt, in which the ocean consist of 90% or more of the area of latitude belt, tire postions of ultra-long waves variate greatly from one year to another, independent of whether they are dominanting or not in this latitude belt.