Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Caracterização espaço-temporal das secas sobre o Brasil nas últimas décadas (1981-2016)

Auteur : Lira Tamires Alybia Gomes de

Université de soutenance : Instituto Nacional de Pesquisas Espaciais – INPE

Grade : Mestrado do Curso de Pós-Graduação em Meteorologia 2019

Résumé
Drought events have caused severe impacts to the environment and society being therefore subject of several studies. Recently, some researches were performed aim ing to investigate droughts throughout their frequency of occurrence, duration and intensity for the Northeast, Southeast and the Northern regions of Brazil. Results have shown that affected areas increased each year. However, how large was the increase over the whole country has not been explored. Thus, this research aims to characterize droughts events in their spatial and temporal aspects over all Brazilian territory during the last decades (1981 - 2016). In addition, possible changes in the atmospheric circulation patterns, modifications in the distribution of the precipita tion and changes in the Sea Surface Temperature (SST) patterns were also inves tigated. For such purposes various datasets were used, including precipitation data from the Multi-Source Weighted-Ensemble Precipitation (MSWEP), Climate Fore cast System Reanalysis (CFSR) for the atmospheric circulation data, precipitation evaporation and vertical velocity (omega) data from the ERA-Interim reanalysis, SST data from Reynolds series and the Vegetation Health Index (VHI) estimated from satellite data. Analyses for the vegetation, precipitation and precipitation evaporation data were based on statistic aspects such as angular coefficients and p value of their quarterly and annual temporal series, which were created using a threshold to specify, in percentage, drought conditions over the country. Tempo ral series that pointed out an increase in the drought areas were chosen to create composites for the other variables, such as circulation, SST and vertical velocity. An expressive increase of the areas affected by droughts conditions was showed in the anual VHI series for the entire period of study, as well as for the last decade in the decenal VHI series. These aspects were reproduced in the quarterly series for the austral summer (DJF), in all indexes analyzed, specially in the last decenal period (2007/08 - 2015/16). The composites for the SST and atmospheric circu lation anomalies indicated that ENSO (El Niño-Southern Oscillation) events were associated with anomalous anticyclonic circulation patterns, especially in the last three years of the decenal serie (2014, 2015 and 2016). Its combined occurrence played an important role in the maintenance and expansion of the areas affected by drought conditions during the summer of the last decenal period, contributing to the increasing of the total area.

Mots Clés  : Drought. Vegetation Health Index (VHI). Climatic diagnostic.

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