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Sumatera occurs by stratiform clouds which are dominant in this period. That is whyprecipitations on 11 June 2002 are dominated by stratiform precipitating clouds. Convectionsat the end of Period 2 (14-16 June) are shallow because surface convergence moves to the eastof Sumatera. In period 3, convections over Sumatera are suppressed by the strong westerly.High surface pressure enlarges surface divergence at the radar site. No cloud activities occurunder those conditions.AcknowledgmentsThe authors thank Frontier Observation Research System for Global Change (FORSGC), Japan, theIndonesian Agency for the Assessment and Application of Technology (BPPT), Indonesia, and the IndonesianMeteorological and Geophysical Agency (BMG), Indonesia, for providing radiosonde data. The EAR belongs toRASC and is operated by RASC and National Institute of Aeronautics and Space (LAPAN), Indonesia basedupon the agreement between RASC and LAPAN signed on September 8, 2000. They also thank all operatorswho maintain the EAR and BLR. The present study was partially supported by Grant-in-Aid for ScientificResearch on Priority Area-764 of the Ministry of Education, Culture, Sports, Science, and Technology (MEXT)of Japan. The first author is financially supported by Loan Japan Bank for International Cooperation (JBIC) -Science, Technology, and Industrial Development (STAID) Program of Indonesian government.ReferencesFujiwara, M. and M. Takahashi., Role of the equatorial Kelvin wave in stratosphere-troposphere exchange in ageneral circulation model, J. Geophys. Res., 106, 22, 763--22, 780, 2001.Fujiwara, M., M.K. Yamamoto, H. Hashiguchi, T. Horinouchi, and S. Fukao, Turbulence at the tropopause due tobreaking Kelvin wave observed by the Equatorial Atmosphere Radar, Geophys. Res. Lett., 30,doi:10.1029/2002GL016278, 2003.Fukao, S., H. Hashiguchi, M. Yamamoto, T. Tsuda, T. Nakamura, M.K. Yamamoto, T. Sato, M. Hagio, and Y.Yabugaki, The Equatorial Atmosphere Radar (EAR): System description and first results, Radio Sci., 38, 1053,doi: 10.1029/2002RS002767, 2003.Gage, K, S., The structure and dynamics of the free atmosphere as observed by VHF/UHF radar, in Radar inMeteorology, edited by D. Atlas, pp. 534-565, American Meteorological Society, 1990.Gage, K. S., B.B. Balsley, W.L. Ecklund, D.A. Carter, and J.R. McAfee, Wind profiler-related research in thetropical Pasific, J. Geophys. Res., 96, 3209-3220, 1991.Hendon, H. H. and M.L. Salby, The life cycle of the Madden-Julian oscillation, J. Atmos. Sci., 51, 2225--2237,1994.Larsen, M. F. and J. Roettger, VHF and UHF doppler radars as tool for synoptic research, Bull. Am. Meteorol.Soc., 63, 996--1008, 1982.Madden, R. A. and P.R. Julian, Observations of the 40-50-day tropical oscillation - A review, Mon. Wea. Rev.,122, 814-837, 1994.Matthews, A. J., Propagation mechanisms for the Madden-Julian oscillation, Quart. J. Roy. Meteor. Soc., 126,2637-2652, 2000.Nitta, Ts., T. Mizuno, and K. Takahashi, Multi-scale convective systems during the initial phase of the 1986/87El Nino, J. Meteor. Soc. Japan, 70, 447-466, 1992.Rao, P. B., A.R. Jain, P. Kishore, P. Balamuralidhar, S.H. Damle, and G. Viswanathan, Indian MST radar 1.System description and sample vector wind measurements in ST mode, Radio Sci., 30, 1125-1138, 1995.Rui, H. and B. Wang, Development characteristics and dynamic structure of tropical intraseasonal convectionanomalies, J. Atmos. Sci., 47, 357-379, 1990.Thomas, L., Aplications of the NERC MST radar facility in mesoscale studies, Meteorol. Appl., 6, 133-142,1999.Williams, C.R., W.L. Ecklund, and K.S. Gage, Classification of precipitating clouds in the tropics using915-MHz wind profilers, J. Atmos. Oceanic Technol., 12, 996-1012, 1995.Wang, B., Dynamics of tropical low-frequency waves: An analysis of the moist Kelvin wave, J. Atmos. Sci., 45,2051-2065, 1988.269