30—50天振荡动能演变及维持机制的诊断分析

DIAGNOSTIC RESEARCH FOR EVOLUTION OF KINETIC ENERGY OF 30-50 DAYS PERIOD OSCILLATION AND ITS PROBABLE MAINTENANCE MECHANISM

本文采用带通滤波的方法,选取赤道附近(5°S—5°N,80—120°E)和中纬度区域(40—BO°N,140—180°E)的平均量作为研究对象,分析动能平衡方程各项的时间演变特征、季节平均的垂直分布特征以及各作用项与动能变化的可能联系。指出30—50天振荡动能的维持主要与平流作用和平均气流的正压相互作用有关,但其输送在赤道和中纬度地区恰好是反方向的。赤道地区是振荡的源,振荡从基本流中获得能量,同时通过平流作用向外输送,振荡动能对各项作用的响应为5—7天;中纬度地区是振荡的汇,向基本流中输送能量,动能变化对各项作用的响应为2—3天。

The data of U, V, T and Z on seven Layers (i. e. , 1000, 850, 700, 500, 300, 200 and 100hPa) from Dec. 1st, 1981 to Feb. 28th, 1982 were chosen for analyzing in this paper. The mean values of these elements in the region near equator (5°S-5°N, 80-120°E) and in the region of middle latitude (40-60°N, 140-160°E) were taken to be objects for research and then the feature of evolution in time of various terms in the kinetic energy equilbrium equation, the feature in vertical distribution of seasonal average and the probable relation between various terms of equation and change of kinetic energy, all of them were analyzed in the research. It showed that the maintenance of kinetic energy of 30-50 days disturbance related mainly to the advection influence and barotropical action of mean flow, but the directions of transfer in equator and middle latitude were reverse. The results also showed that the equator region was the disturbance source, energy was obtained from basic flow and that the response time for influnce of various terms was 2-3 days. But the middle latitude was the disturbance sink, where the energy in basic flow was consumed. The response time for various terms was 5-7 days.