Thursday, 27 October 2005
Alvarado F and Atria (Hotel Albuquerque at Old Town)
The Amazon basin covers an estimated area of 6,3 million square kilometers, of which almost 80% is located in the Brazilian territory, with the rest shared by Bolivia, Colombia, Equador and Peru. This region is bounded by the Andes Mountain Range in the west (elevations up to 6000 m), the Guianas Highlands in the north (with peaks up to 3000 m), by the Central Highlands in the south (typical heights up to 3000 m) and in the east by the Atlantic Ocean, where all the water captured in the Amazon basin flows to. The Amazonia area comprises nine provinces, viz., Pará, Amazonas, Rondônia, Roraima, Acre and Amapá, as well as parts of Tocantins, Mato Grosso and Maranhão. The convection in the Amazon region is an important mechanism of the tropical atmospheric heating and its variations, in terms of intensity and position, but also plays an important role in the characterization of the weather and climate in this region. Following these considerations, the System for the Protection of Amazonia (SIPAM) was created, based mostly on the remote sensing technology for data collection over the whole region. The system comprises a network of automatic weather stations and upper air soundings, as well as a network of 10 S-band Doppler radars, strategically distributed over the Amazon forest. This network of meteorological radars has provided a unique opportunity for the meteorologists of the Operational Meteorological Division of SIPAM, based in Manaus, for monitoring a squall line, which occurred on 17 January 2005. This squall line had propagated from south-west, originating in the Tefé/Coari/Codajás regions, together with another instability line, originating in Boa Vista and approaching from north-west. It was monitored by at least 4 radars of the SIPAM network. The squall line activity lasted for more than 12 hours and was intensifying during its displacement over the Amazon river area, with a well-defined convective leading edge, with individual cells exceeding 50 dBZ, followed by an extensive stratiform region. In the city of Manaus, the surface station at Eduardo Gomes Airport reported a sudden drop in temperature, from 35º C to 24º C, between 14:00 and 16:00 LT (LT=UT-4h), followed by wind gusts of around 70 km.hr-1. The accumulated rainfall for this event was between 12 and 18 mm.
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