Variabilidade de baixa frequência nos modos do oceano atlântico tropical e seus efeitos na precipitação da américa do sul tropical: 1901-2015

Abstract

Sea Surface Temperature (SST) variability patterns in the tropical Atlantic Ocean (TA) and their relationship to low frequency variability modes as well as their influence on South America (AS) were evaluated during the period of 1901 - 2015, using Empirical Orthogonal Function (EOF) and composites method. Meridional and zonal patterns are the dominant modes in interannual timescale that overlaps multidecadal variations. Regarding the zonal mode, it was possible to show that it is highly correlated to the North Atlantic TSM variations associated with the Atlantic Multidecadal Oscillation (AMO). During periods when meridional mode and AMO are in the positive (negative) phase, the meridional pattern is evident all the seasons, from March to May (MAM), June to August (JJA), September to November (SON) and December to February (DJF), keeping the Intertropical Convergence Zone (ITCZ) to north (south) of its climatological position, which affects the precipitation regime over the north and northeast regions of South America. When the meridional mode and AMO are out of phase, meridional mode pattern is shown only from March to May (MAM). Regarding the zonal mode, it was observed that it is correlated with changes in the TSM in the AT and Pacific oceans, setting the pattern of zonal interbasins, mainly in the JJA and SON quarters with negative statistics on northern AS if running. to the NEB. This pattern is best during the period from 1980 to 2015, when the low frequency oscillations associated with AOM in the Atlantic and Decennial Oscillation in the Pacific (ODP) are evident. Billing for the same period has different characteristics for both quarters, with a difference in MAM over NEB. In contrast to the JJA and SON quarters or the catch pattern, which is a zonal strip along the north coast to the NEB associated with intermediate basins and finally, the DJF was observed in the price reduction over the northern Amazon. When you remove the ENSO signal, the seasonal capture pattern for the period 1901-1979 remains, having only a reduction in the correlation pattern, or responding rapidly using ZCIT in response to the established zonal mode. On the other hand, for the period from 1980 to 2015, Walker’s circulation is weakened in the JJA and SON quarters, thus resulting in the weakening of the pattern.