Simulação paleoclimática com ênfase sobre a América do Sul

Abstract

In this work were performed two climate simulations using Atmosphere General Circulation Model (AGCM) from CPTEC, where the objective was to reconstruct the climate through 30 years for the mid-Holocene (6k) and the present (0K). To perform the simulations was activated parameter Berger (1978) which was calculated insolation considering variations in orbital parameters (Milankovich cycle) between the two periods. The CO2 concentration 0K used in the simulation was 370 ppm while the 6K experiment was 280 ppm, based on the results of these simulations were plotted surface fields of mean monthly, seasonal and yearly difference between 6K and 0K, where in order to validate the simulations was confronted with the results of the Paleoclimate Modeling Intercomparison Project data (PMIP), paleoclimatic indicators and other works. This work was calculated ISO to determine the frequency of ENSO in the simulations where the determination of the phases of the PDO occurred by calculation a moving average of 24 months and through of the precipitation fields and current lines was determined indirectly the Atlantic Dipole Index. Aiming to quantify South America (SA) with emphasis on the Northeast of Brazil (NEB) and the Amazon were analyzed annual and seasonal averages of the variables rainfall, air temperature, latent heat flux and sensible heat flux and the vorticity field lines and current levels of 950, 500 and 200 hPa. The results indicate that it was possible to test the synergy of orbital parameters and CO2 in the two scenarios, where we found that the austral summer began in September. We observed that the occurrence of ENSO was more intense during middle Holocene (MH) and the phases of the PDO were less durable. The Atlantic was identified positioning further south of the ITCZ which suggests that during the MH Dipole had a greater negative frequency favoring rainfall in northern NEB and the Amazon. In as was noted that a significant reduction in rainfall over the Amazon region and between the months of December and February the NEB was wetter when compared to the current climate, it was also found that the occurrence of the SACZ was reduced or possibly nonexistent to a lower actuation during the MH jet streams of low level and the lowest amount of latent heat at the surface of the Atlantic coast of Brazil.