Characterization of the South Atlantic Subtropical Anticyclone with different data sources

Abstract

In the subtropical regions of the planet, there are semi-permanent high-pressure systems, known as anticyclones or subtropical highs. Being a descending branch of the Hadley cell, their seasonal variation can impact on the atmospheric conditions of the continents, inhibiting convection and bringing stability. In this study, we used seven atmospheric reanalyses (ERA5, ERA20, 20th Century Reanalysis, MERRA2, CFSR, JRA-55, NCEP/NCAR Reanalysis 1) to characterize the South Atlantic Subtropical Anticyclone (ASAS) through positioning and coverage covering a period from 1836 to 2021 with the Mean Sea Level Atmospheric Pressure (MSPL - hPa) variable. Using seasonal correlation analysis (between 1981-2010) and tracking of its central position, we identified high correlation values in the intensity of the ASAS center among all reanalyses, while the agreement of the latitudinal position presented moderate correlation values. When analyzing the positioning of the ASAS throughout the period, a positioning trend towards the south and west was observed when comparing it with the 1981-2010 climatology. Since the reanalyses have different data assimilation schemes and the results are influenced by the views of the coupled models, the variation observed in the result was expected and indicates an advance between the first and fifth generation reanalyses, mainly in the horizontal resolution. The positioning trends for the present corroborate previous studies using observed data and atmospheric model simulations.