热力强迫下大气平衡态的突变与季节变化、副高北跳

本文研究了具有连续季节变化热力强迫的低阶正压耗散系统的平衡态和平衡态的突变。由此得到,大气环流的典型季节性平衡态是冬季型环流和夏季型环流。由于热力强迫和大气非线性运动的相互作用,随着热力强迫参数的连续季节变化,可以出现大气环流的多次的季节性突变和副热带高压的北跳。在不同的经向和纬向热力差异下,副热带高压可以出现不同类型的北跳。     

旋转地球上二维板对称耗散扰动的非线性不稳定性

本文用五分量的低阶截谱,研究了旋转地球上耗散系统在平均温度场强迫下,二维板对称扰动的非线性不稳定性,得出了蝴蝶型突变。对于指定的水平温度梯度值,随静力稳定度的减小,系统平衡态一般经历从静止单稳态向一定环流强度单稳态的突跳,以后又稳定在强环流的双稳态;而且不出现周期和非周期变化现象。当水平温度梯度不存在时,则只要有一定的较弱的垂直涡粘性,系统本身的非线性作用和环境的静力不稳定性,就可导致周期或非周期变化。     

NON-LINEAR DYNAMIC INSTABILITY OF TWO DIMENSIONAL SLAB SYMMETRIC DISSIPATIVE DISTURBANCES ON ROTATING EARTH

The non-linear instability of the two-dimensional slab symmetric disturbances of the dis-sipative system on the rotating earth subject to the forcing of the mean temperature field isinvestigated by means of the 5 modes low order truncated spectrum. We get the catastropheof the butterfly type. For a given definite value to the horizontal temperature gradient, withthe decrease of the static stability, the equilibrium state of the system generally proceeds start-ing from a quiescent single stable state, then abruptly jumping to the single stable state witha circulation of a certain strength, hereafter again residing stably in the double stable state ofstrong circulation. Moreover, there does not appear the periodic and non-periodic variation.Without temperature gradient, only a definite and comparatively weak vertical eddy viscosityin conjunction with the non-linear mechanism of the system itself and the linear static insta-bility of the environment can lead to the periodic or non-periodic variation.     

CATASTROPHE THEORY OF SEASONAL VARIATION

This paper studies the abrupt change of equilibria state and the equilibria state of low order, barotropical and dissipative system under thermal forcing that have successive seasonal variation. The typical seasonal equilibria of atmospheric circulation are winter and summer circulations. Owing to thermal forcing and nonlinear interaction of atmospheric motion, the atmospheric circulation appears several seasonal abrupt and northward jumpings of subtropical highs with the seasonal variation of the thermal forcing parameter. In various meridional and zonal thermodynamic differences, the subtropical highs can appear different northward jumpings.