Aspectos dinâmicos da atmosfera associados a seca de 2012- 2016 no Nordeste do Brasil

Abstract

Identify the atmospheric circulation patterns that influence drought development contribute to mitigate the impacts on society. In the Northeast Brazil (NEB), one of the most vulnerable regions to extreme events in South America, the occurrence of droughts events is widespread and recurrent. This was the scenario observed during 2012-2016, which an extreme drought struck the region. In this sense, the research aims were to analyze the drought dynamics associated with severe drought event in NEB during 2012- 2016, as well as verify if the tropical band configuration of the RegCM (RegCMTBAND) was able to reproduce the negative rainfall anomalies over the NEB from 2012 to 2016. Anomaly charts and composites of meteorological variables from 1981 to 2016 were used to found out the area of the NEB where the drought was most severe and the large-scale dynamics responsible for it. The RegCMT-BAND model were driven by ERA-Interim data for the initial and boundary atmospheric conditions and sea surface temperature were taken from NOAA_OISST_V2 reanalysis. Analysis of model output skill was done by using the ERA5 reanalyze for atmospheric variables, and Global Precipitation Climatology Project (GPCP) and Xavier dataset to precipitation. The results show this drought event was influenced mainly by two distinct ocean conditions. These conditions drove the atmospheric circulation pattern, where it was observed that from 2012 to 2014 the negative precipitation anomalies were related to strengthened downward motion of the Hadley cell near the equator, while from 2015 to 2016 the precipitation deficits were linkage through a descending branch of the Walker circulation over NEB and also by the subsidence movements associated with the positioning of the Intertropical Convergence Zone (ITCZ). In relation to regional climate model, the RegCM-TBAND indicate reasonably well the sub-region where the drought event was more intense, and represent quite satisfactorily the amount of negative precipitation anomalies in the driest years. Therefore, this study showed results encouraging the use of RegCM-TBAND to study extreme events associated with droughts conditions in the Northeast region of Brazil.