Impact of Position and Horizontal-Scale of Strong Convection Area on the Low-Frequency Oscillation in the Tropical Atmosphere

doi:10.7523/j.issn.2095-6134.2002.1.007

Abstract

Abstract:

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

CLC Number:

P461.2

CUI XueFeng, HUANG RongHui. Impact of Position and Horizontal-Scale of Strong Convection Area on the Low-Frequency Oscillation in the Tropical Atmosphere[J]. , 2002, 19(1): 49-58.

References

[1] Madden R D, Julian P.Det ect ion of a 40～50 Day Oscillation in the General Wind in the T ropical Pacific.J Atmos Sci, 1971, 28:702～708.

[2] Madden R D, Julian P.Description of Global Scale Ci rculation Cell in T ropics w ith 40～50 Day Period.J Atmos Sci, 1972, 29:1109～1123.

[3] Chang C P, Lau K M.Northeast erly Cold S urges and Near Equatori al Disturbances over WinterMONEX During Dec.1974, Part Ⅱ:P lanetary S cale Aspects.Mon Wea Rev, 1980, 108:298～312.

[4] Sumi A, Murakami T.Some Problems on the Monsoon.Met eorological Notes, 1984, 149.

[5] Lau K M, Chan P H.Aspects of the 30～50 Day Oscillat ion During the Northem Hemisphere Winter as Inf erred form Outgoing Longw ave Radiation.Mon Wea Rev, 1985, 113:1889～1901.

[6] Nakazaw a T.Mean Features of 30～60 Day Variat ions as Inferred f rom 8-year OLR Data.J Meteor S oc Japan, 1986, 64:777～786.

[7] Yasunari T.Sturct rue of an Indian S ummer M onsoon System w ith Around 40-day Period.J Met Soc Japan, 1981, 59:336～354.

[8] Murakami T, Nakazaw a T, He J.On the 40～50 Day Oscillat ion Du ring the 1979 Northern Hemisphere Summer, Part I:P hase Propagation.J Met eor Soc Japan, 1984, 62:4460～4468.

[9] Murakami T.Tropical 45-day Oscillat ion Du ring the 1979 Northern Hemi sphere S ummer.J At oms Sci, 1985, 42:1107～1122.

[10] Huang R H.Interactions Betw een the 30～60 Day Osci llation, the Walker Ci rculation and the Convecti ve Activities in the Tropical Wesern Pacific and thei r Relation to Int erannual Oscillation.Adv At oms Sci, 1994, 11:367～384.

[11] Krihnamurt i T N, Bhalme H N.Oscillation of a Monsoon System,Part I:Observation Aspect s.J Atoms S ci, 1976, 33:1937～1954.

[12] 陈于湘.夏季西太洋越赤道气流的谱分析.大气科学, 1980, 4:363～368.

[13] 李崇银, 周亚萍.热带大气中的准双周(10～20 天)振荡.大气科学, 1995, 4:435～444.

[14] Li C Y.Quasi-tw o Week Oscillation in the Tropical Atmosphere.T heoretical and Applied Climat ology,1996 a, 55:121～127.

[15] 李崇银, Smith I.热带大气(10～20 天)振荡的大气环流模式数值模拟.大气科学, 1996b, 19:63～72.

[16] Chang C P.Viscous Int emal Gravit y Waves and Low-f requency Oscillat ions in the Tropi cs.J Atoms S ci, 1977, 34:900～910.

[17] 李崇银.南亚夏季风槽脊和热带气旋的活动性与移动性CISK 波.中国科学, 1985, B 辑:1197～1207.

[18] Lau K M, Peng L.Origin of Low-f requency (Int raseasonal )Oscillations in the Tropi cal Atmosphere, Part I:Basic Theory.J Atoms Sci,1987, 44:950～972.

[19] Liu A D, Huang R H.A Sim ple Model and Numerical Simulat ion of Lowfrequency Oscillat ion in the T ropical Atmosphere.Chinese J AtomsSci, 1994, 18:115～126.

[20] Miyahara S.A Simple Model of the Topical Int reseasonal Osci llations.J Met Soc Japan, 1987, 65:341～351.

[21] Gill A E.Some Simple Solutions f or Heat-induced T ropical Circulati on.Quat J Roy Metor S oc, 1980, 106:447～462