TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 61 (No. 4), pp. 535-544, 2009

Diurnal and intraseasonal variation of UTLS vertical wind disturbance in the equatorial region and its relation to tropospheric convective activities

Toshiaki Kozu1, Yasu-Masa Kodama2, Yoshiaki Shibagaki3, Toyoshi Shimomai1, Masayuki Kawashima4, and Simon P. Alexander5

1Shimane University, Matsue, Shimane 690-8504, Japan
2Hirosaki University, Hirosaki, Aomori 036-8561, Japan
3Osaka Electro-Communication University, Neyagawa, Osaka 572-8530, Japan
4ILTS, Hokkaido University, Sapporo, Hokkaido 060-0819, Japan
5Australian Antarctic Division, Kingston, Tasmania 7050, Australia

(Received November 25, 2007; Revised September 9, 2008; Accepted September 15, 2008; Online published May 14, 2009)

Abstract: Vertical wind variations in the Upper Troposphere and Lower Stratosphere (UTLS) measured by the Equatorial Atmosphere Radar (EAR) at Kototabang, Sumatra, between 2003 and 2005 but mainly in 2004, have been statistically analyzed to study the characteristics of wind variances associated with convective activity, which is related to gravity wave generation and propagation. The analyses are intended to characterize relatively short period disturbances of less than 12 hours and an energy propagation direction of a relatively high elevation angle, and to relate vertical wind variations to convective activity close to the EAR. Correlation analyses between vertical wind variations and rainfall show that the wind variances have a clear diurnal variation indicating probable effects of tropospheric convection. They also show some intraseasonal variation. However, there are no significant correlations with the Out-going Long-wave Radiation (OLR) anomaly. The correlations between variances at UT and LS suggest that the UTLS coupling of vertical wind variation through upward propagation of gravity wave is similarly evident in the afternoon during both the active and the inactive phase of OLR that is a proxy of large-scale convective activity.
Key words: Vertical wind, gravity wave, equatorial region, tropospheric convection, rainfall.

Corresponding author E-mail: kozu@ecs.shimane-u.ac.jp

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