Tendências de parâmetros convectivos no sul do Brasil: uma análise preliminar

This study is a preliminary investigation, for southern Brazil, about possible changes in the last four decades in the magnitude of two convective parameters indicative of atmospheric environments favorable to severe convective storms. The parameters selected for this research, the convective available potential energy (CAPE), and the magnitude of the vector wind difference between the surface and 6 km above ground level (DLS), are, respectively, indicative of the presence of conditional instability and vertical wind shear in a deep layer. These parameters were computed for hourly tropospheric profiles (or pseudo-soundings) extracted from the native vertical grid of the ERA5 reanalysis for the period between 1980 and 2021 for the grid points nearest to the three state capitals of southern Brazil: Curitiba, Florianópolis and Porto Alegre. The analysis, for each location, of the trend in the time series of CAPE and DLS, averaged for every single month, was carried out with the aid of the non-parametric Mann-Kendall test. The results obtained from the tropospheric profiles of the ERA5 reanalysis reveal a negative trend in the extreme values of CAPE, especially for Porto Alegre, but accompanied by an increase in the magnitude of DLS for all locations. Therefore, in this preliminary analysis, the implications from CAPE and DLS for the conditioning of environments favorable to severe storms display opposite signs for the selected locations. Additional research addressing the frequency of environments conducive to severe storms is needed for a more complete assessment of the impact of these trends.