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Impact of Position and Horizontal-Scale of Strong Convection Area on the Low-Frequency Oscillation in the Tropical Atmosphere
Received date: 2001-06-14
Revised date: 2001-10-29
Online published: 2002-01-10
The influence of position and horizontal scale of strong convective activities on the low frequency oscillation in the tropical atmosphere is discussed by using a simple three-dimensional numerical model of the tropical atmospheric motion including the wave CISK mechanism.The results show that the meridional position of strong convective activities has an important impact on the low frequency oscillation in the tropical atmosphere.When convctive activities are intensified over the equatorial Indian Ocean and the equatorial westerm Pacific,the oscillation excited by the intemal heating propagates eastward form the equatorial Indian Ocean and has a period of about 28 days, and its disturbance exhibits the combined Kelvin Rossby wave pattern and has an obvious baroclinic structure with the convergence in the lower atmosphere and the divergence in the upper atmosphere.However,when convective activities are intensfied over the tropical Indian Ocean and the tropical western Pacific around the Philippines,the oscillation excited by the internal heating propagates westward from the tropical western Pacific and has a period of about 30 days,and its distrubance has weaker baroclinic structure than that excited by the heating in the equatorial atmosphere,and it exhibits the Rossby wave pattern,which is closely associated with the South Asian summer monsoon.Moreover,the results show that a period and structure of oscillation is not dependent upon the zonal position of strong convective activities.The results also show that the horizontal scale of strong convection area has an obvious influence on the period of the low frequency oscillation in the tropical atmosphere.The strong convective activities over a smaller convection area can excite the low frequency oscillation with a smaller period.This can explain that the 10～20 days oscillation in the tropical atmosphere may be excited by the convective activities over a smaller convection area.
Key words： low frequency oscillation; convective activities; Rossby wave; Kelvin wave
CUI XueFeng , HUANG RongHui . Impact of Position and Horizontal-Scale of Strong Convection Area on the Low-Frequency Oscillation in the Tropical Atmosphere[J]. Journal of University of Chinese Academy of Sciences, 2002 , 19(1) : 49 -58 . DOI: 10.7523/j.issn.2095-6134.2002.1.007
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