对流层大气环流的甚低频振荡

VERY LOW FREQUENCY OSCILLATIONS IN THE VARIATIONS OF TROPOSPHERIC ATMOSPHERIC GENERAL CIRCULATION

对１９５１—１９９２共４２ａ５００ｈＰａ北半球高度场的月平均资料进行了纬圈谐波分析，计算了３５°Ｎ与５５°Ｎ超长波振幅及位相，以及３５—５５°Ｎ北半球月平均纬向风距平百分比。对超长波振幅及纬向风距平百分比做了小波转换。结果表明，对流层大气环流变化中存在３种准周期性的甚低频振荡：１．年代际的振荡；２．准２ａ周期振荡（ＱＢＯ）；３．半年韵律。同时发现对流层ＱＢＯ和平流层赤道纬向风ＱＢＯ之间可能没有联系。

Based on the monthly mean 500hPa maps over the Northern Hemisphere for 42 years (1951-1992),zonal harmonic analysis at 35°N and 55°N were carried out and westerly intensities between 35-55°N were calculated. Meanwhile,wavelet transform of percentage departures of westerlies and relative amplitudes of ultra-long wave were analyzed.Then,three kind of very low frequency oscillations were identified in the variations of tropospheric general circulation.1.Interdecadal oscillation;2.Interannaual oscillation (QBO) and 3.One-year osculation.Interdecadal oscillation maybe exists in wave-1 with 30-40 year oscillation and wave-3 with 20-year oscillation at 35°N. QBO with 2. 5-2. 6 year oscillation were showed in westerlies as well as wave-2 and wave-3 at 55°N, but no any direct relationship with stratopheric QBO(2.2 year) was found out.Maybe, the QBO in middle troposphere is caused by the interactions between the atmosphere and ocean or between the atmosphere and land surface. It may belong to auto-oscillation of the climate system. After wavelet transform,the one-year oscillation in some ultra-long waves and westerlies were more outstanding. It reflects a kind of rhythm in atmosphere,such as warm-winter and cool-summer and vice versa. It is also an adjustment inner the climate system,which closely relates to the seasonal course of the general circulation.