2006 年 84A 巻 p. 19-31
A special tropospheric observation was conducted during 10 April-09 May 2004 as a part of the first campaign of the Coupling Processes in the Equatorial Atmosphere (CPEA-I), using upper soundings at seven stations in/around Sumatera, and weather radar and wind profilers at Kototabang (KT; 100.32°E, 0.20°S, 865 m above mean sea level), West Sumatera. A super cloud cluster (SCC) with a westerly wind burst (WWB) propagated eastward over the Indonesian Maritime Continent during 04-07 May. In the present report, we examine the evolution of that SCC and the associated wind behavior in detail, using Geostationary Operational Environmental Satellite (GOES-9) Infrared (IR) data and CPEA observations. During the analysis period, the SCC developed over the eastern Indian Ocean, decayed rapidly as it reached Sumatera, and re-developed over Kalimantan. The eastward propagation of SCC resulted from the successive formation of meso-scale cloud clusters (CCs) with westward propagation. The transition of the SCC was related to the evolution of CCs. A CC generated over Sumatera began to diminish as the WWB arrives at a mountain range in western Sumatera, but it dominated in/around the mountain range for ∼9 hours. From upper sounding data aligned along the equator, it was found that the migration speed of the WWB over Sumatera was approximately half that over the sea region between Sumatera and Kalimantan, due to the orography of the Indonesian Maritime Continent. In western Sumatera, the peak height of the WWB at the mountain range ascended 1.5 km from that on the windward side. This shows that the eastward migration of the WWB was intercepted by the mountain range. The orographic influence on the WWB is considered to persist during the retention of the CC in its vicinity. Further, we reveal features of the orographic precipitation associated with the WWB and the detailed wind structure inside the SCC over the mountain range, from radar observations at KT.
