Comportamento dos fluxos horizontais de vapor d’água na Bacia Hidrográfica Mirim-São Gonçalo

Abstract

The Mirim-São Gonçalo Hydrographic Basin (MSGHB) is a transboundary basin of utmost importance for its region, as it includes several municipalities in the state of Rio Grande do Sul whose economy is based on agriculture, an activity closely linked to the climatic conditions of the region. region. Therefore, it is essential to study climate variables and how they can impact the development of society, especially in the economic part. Water vapor fluxes are important atmospheric constituents not only in terms of the greenhouse effect, but also in their relationship with precipitation regimes. Therefore, the present work aimed to evaluate variability and the preponderant direction of water vapor flows in the Brazilian part of the Mirim – São Gonçalo Hydrographic Basin based on ERA5 reanalysis data for the period from 1981 to 2020. The values generated in ERA5 showed high correlation with observed precipitation data, thus indicating the efficiency of the model. With the analysis of vertically integrated water vapor flow (iwvf) it was found that the preponderant flows in the BHMSG are from the north and west, and at low levels (925hPa) the influence of humidity from the South Atlantic Ocean is observed in the months from September to March. It was also found that there is a direct relationship between iwvf and precipitation regimes, where the higher the iwvf in BHMSG, the greater the volume of precipitation, which varies according to seasonality. The maximum extreme precipitation events presented higher iwvf values on the four faces, where the north face stands out, with a value twice as high as the climatological normal, and the opposite was observed for the minimum extreme events, where in this case, the north face presents iwvf three times lower than its normal value. The vast majority of extreme precipitation events occurred in periods where the El Niño-Southern Oscillation phenomenon was classified as neutral. Such results can assist in planning, decision making and management of water resources in the river basin.