Identificação de tendências na precipitação e atividade ciclônica na América do Sul

Abstract

This study presents the main climatological characteristics and trends, for precipitation, considering extreme rates, and cyclonic activities, in South America and the South Atlantic, respectively. Precipitation analysis was performed from data provided by the Climate Prediction Center (CPC-NOAA) in the period 1979-2019. Cyclone tracking was performed considering data from reduced pressure at sea level from 6 different reanalyses, including two centenaries ones. From cyclones tracked in simulations for present and future climate from The Coupled Model Intercomparison Project Phase 5 (CMIP5), the climatological characteristics and trends for the different types of cyclogenesis were analyzed. The classification of cyclogenesis types is carried out in three stages: the first to identify and track cyclones in the South Atlantic Ocean based on the relative vorticity at 925 hPa; application of the Cyclone Phase Space methodology to synthesize the thermal structure of the cyclones and finally, separate the cyclones based on their thermal characteristics. The main results of this study show that in a large part of South America, mainly in the band that extends from the Amazon towards the southeastern region of Brazil (region of the Prata basin), the trends indicate less (greater) availability of water in the cycle hydrological. For cyclonic activities, reanalysis with higher resolution are the ones that provide the greatest number of cyclones, but this does not affect the climatological characteristics. For the entire Southern Hemisphere, the NCEP20C shows a positive and statistically significant trend in the frequency of cyclones, while the ERA20C indicates a negative trend. For Intense cyclones (reaching central pressure less than 980 hPa) showed an increasing trend in all reanalyses. Considering the different types of cyclones, for the period 2020-2050 (2051-2080), the ensemble of Global Circulation Models (MCGs) and dynamic downscaling using RegCM4 project a slight reduction (increase) in the frequency of tropical cyclones when compared to the present climate (1979- 2005). One of the initial hypotheses of the study was that in a warming scenario, there would be an increase in the number of TT, however the results obtained do not indicate a change in the frequency of these systems since in both the present and future climate the number of transitions is ~ 2.8 systems per decade in both ensembles.