LOCAL ATMOSPHERIC CIRCULATIONS IN THE AMAZONAS RIVER MOUTH Diego Oliveira de Souza Fundação Universidade Federal do Rio Grande, Rio Grande, Brazil Laboratório de Meteorologia - GEPRA e-mail: pgofdos@furg.br Jaci M. B. Saraiva Sistema de Proteção da Amazônia, Manaus, Brazil e-mail: jsaraiva@mn.sivam.gov.br 1. INTRODUCTION The estuarine systems have an historic and fundamental importance for the development of mankind. About 2/3 of the planet mega-cities, for example, are in proximities of estuaries. These systems are responsible by the supply of important nutrients for the development of life in the oceans, and in these systems are located great harbor poles, as an example we have Santana Harbor in Amapá and Belém Harbor in Pará. The region of the Amazon River mouth is rich in mangrove swamps, the main responsible by the protection of the cost line from storms, besides being a protection for several marine and estuarine species. These environments are over the influence of meteorological phenomena that vary since a micro-scale till a synoptic scale. We can notice that the main tempest causer phenomenon is the squall lines. According to Cohen (1989), the squall lines (SL) that are formed in the Atlantic Cost of Amazon are responsible by the formation of rain near the cost of the States of Pará and Amapá, as well as in Central Amazon. The SL is characterized for having a great conglomerate of cumulus-nimbus clouds and it is formed through the coast because of the circulation of sea breeze. The shift of SL in east direction to west is due to a phenomenon called east waves, that according Riehl (1954), are oscillations in pressure fields and wind that are in phase in the surface, which carry the perturbations in its propagation direction. According to the author, these waves have a phase speed of 6° of longitude a day, period from 3 to 4 days and wave horizontal length from 2000 km to 3000 km. Ezpinoza (1996), using meridional wind data, for a period of 10 years, showed that these ondulatory disturbances exist through all the year with different wave length and that during the summer (DJF), autumn (MAM) and winter (JJA) they move themselves arriving in the north northeast coast of Brazil. According to the same author, on summer the wave length is from 6000 km to 7000 km, and the phase speed is from 10m/s to 14m/s and on autumn the wave length is from 5000 km to 6000 km and the phase speed if of 10 ms-¹ to 13 ms-¹ and on winter the wave length are shorter, varying from 3500 km to 4000 km and the phase speed from 10 ms-¹ to 13 ms-¹. As notice previously, the marine breeze is one of the main forming mechanisms of SL. Among the local wind systems, the sea, lacustrine and land breezes are typical systems of littoral regions, or near to great water bodies. This kind of circulation is basically induced by the difference of daily heating between the land and water surface. It is also influenced by the topography, by the coast curvature, by the local latitude, besides of the synoptic conditions and the climatologic circulation of large scale (Saraiva, 1996). The circulations of breeze kind are known as local circulations. Their formation is basically due to the difference of temperature between the land and water surface. During the day the land receives about 51% of all the radiation emitted by the sun. This percentage will heat the land and water surface, but this heating is in a different way because the land and the water have different capacities to store the heat. During the day the land have to heat itself faster than the water, occurring then a difference of temperature between them. According to Kousky and Dias (1982), the high specific heat and the high water transparence act together maintaining the surface temperature in an almost constant value. Part of the heat received by the water is also used in the process of evaporation making that the surrounding air stay relatively cold. Due to this temperature difference between the land and water surface, there will be a circulation with its direction according to the 1417 Proceedings of 8 ICSHMO, Foz do Iguaçu, Brazil, April 24-28, 2006, INPE, p. 1417-1425.