Mecanismos físicos da influência da temperatura da superfície do mar no Pacifico e Atlântico tropicais sobre as chuvas no norte do Nordeste brasileiro.

Abstract

The quality of the rainy season in the Northeast can be related to the variability that arises in from of the phenomenon El Niño-Southern Oscillation (ENSO). That influences the rainy season by both the change in Walker's cell and by teleconnection patterns. The latter are responsible for causing variability in the sea surface temperature (SST) in the North Atlantic, by means of wave train patterns, which may influence the displacement and time of permanence of the Intertropical Convergence Zone (ITCZ) in these latitudes. This further northward shift of the ITCZ may lead to the formation of a thermally direct cell with its branch of subsidence south of the equator. Precipitation in the rainy season in the Northeast can still be influenced by the variability of SST, sea level pressure (PNM) and wind over the Atlantic basin. This variability also affects the positioning of the ZCIT, both because it influences the inter - hemispheric SST gradient and the positioning of the trade-offs. In this work was sought to improve the understanding of how these mechanisms combine, and whether there is predominance between them. In an initial stage we analyzed compounds of a set of variables for situations of El Niño, La Niña and neutral Pacific. The aim was to investigate the main mechanisms controlling the Atlantic variability in these different cases. It is possible to observe that in the positive and negative phases of the ENSO the great variability in the extratropics stands out for the small variations in the tropical region and that the anomalies of the heat flow were influenced by the positive feedback mechanism. For the neutral Pacific the variability in the tropics seemed to be more noticeable and the variation of the heat flow occurred by the temperature variation at the ocean-atmosphere interface. Some case studies were then made. That is, we analyzed specific years with respect to the anomalies in the cells of Hadley, Walker, heat flows, SST, geopotential, wind and precipitation. Thus, the effects of ENSO teleconnections are influenced in different ways depending on the intensity of the phenomenon. For the years studied, one of the main mechanisms of variability for SST in the tropical region was the positive feedback mechanism. However, for the year in which the inter-hemispher ic gradient was well defined, the temperature variation at the ocean-atmosphere interface was the main force for the heat flow anomalies. Showing that the variability mechanism will change from year to year depending on the SST anomalies. The results show that the North Atlantic and Southern Tropical Atlantic basins tend to respond to variability with different mechanisms from year to year.