In Northeast Brazil (NEB), severe droughts have high socioeconomic impacts. In this study, the spatial–temporal characteristics of drought were evaluated based on a new drought index at 4‐km spatial resolution, derived from regional empirical relationships between a remote sensing‐based index and rain‐gauge‐based standardized precipitation index (SPI), a well‐known drought meteorological index. This index was used to compare the spatial pattern of severe drought events (1982–1983, 1992–1993, 1997–1998, and 2012–2013) of the last 30 years. Strong El Niño related droughts were found to be generally spatially limited, affecting around 30% of NEB and concentrated in the northern part of the region, while 2012 drought, which was not El Niño related, was widespread, reaching 46% of NEB. These results stressed the importance of analyzing droughts at the subregion scale using data with higher spatial resolution. Statistically significant trends (p < 0.05) toward drier conditions detected in the SPI time‐series were linked to the tropical Atlantic Ocean warming trend, which result in an increased drought risk and social vulnerability in the region.

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ABSTRACT:A new method to determine the onset dates of the rainy season (ONR) in the Central Amazon area using the antisymmetric in relation to the equator outgoing longwave radiation (OLR) data was developed in a previous paper. This method is adjusted and used here to determine the ONR in Western-Central Brazil (WCB). The adjustment is needed because of the northwest-southeast (NW-SE) orientation of the American monsoon-related convection displacement. The area averages of the OLR (AOLR) are used to identify the ONR dates. The ONR dates in WCB based on the precipitation index determined in a previous work are used as reference for comparisons. The differences between the results with the AOLR method and those shown in previous papers, as well as the advantages of this method are discussed, using composite maps of OLR and maps of the Tropical Rainfall Measuring Mission (TRMM) precipitation data for individual years. The results obtained here for the WCB indicate a potential of the new method for monitoring purposes because the OLR data can easily be obtained and the AOLR calculation is very simple.

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No intuito de suprir as necessidades do consumo interno de azeite e azeitona, muitos produtores no Brasil, mais especificamente no sul de Minas Gerais, têm investido nesse cultivo. Entretanto, para viabilizar a expansão da olivicultura é necessário conhecer as condições climáticas limitantes ao seu cultivo, principalmente em relação a eventos extremos de temperatura e precipitação; que são os maiores limitantes à olivicultura. Por isso, o objetivo deste estudo é determinar as áreas climatologicamente aptas ao cultivo da oliveira, em Minas Gerais. Para isso, foram calculadas as climatologias mensais de precipitação e das temperaturas média, máxima e mínima do ar; para o período de 1981 a 2010, em 49 estações meteorológicas de Minas Gerais. Também foram calculados os percentis para determinação de eventos extremos de precipitação (P5 e P95), temperatura máxima (T90) e mínima (T10); além de contabilizar o número de casos com temperatura inferior a 9,5°C e superior a 30°C. Por fim, foi analisado a relação da quantidade dos eventos extremos com as fases fenológicas da oliveira. Os eventos de temperatura inferior a 9,5°C, ocorrem com maior frequência (≥1500 eventos) na região sul do estado. Com relação a eventos de temperatura superior a 30°C, há um maior número de casos (≥1000 eventos) no noroeste, norte, Vales do Jequitinhonha e Mucuri, Central e Triângulo Mineiro. Já a precipitação não inviabiliza o cultivo de oliveira em Minas Gerais, principalmente pela possibilidade de irrigação suplementar nas regiões com maiores registros de P5 e pelo pequeno número de casos (≤ 24 eventos) de P95. Somente as regiões sul e pequena parte do centro-oeste de Minas Gerais possuem características climáticas favoráveis ao cultivo de oliveira

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The relations of both nodes of the tropical Atlantic (TA) cross‐equatorial sea surface temperature (SST) gradient (GRAD) mode to the climate of northeast Brazil (NEB) during the 1901–2012 period are examined separately. The GRAD mode consists of a SST anomalous pattern anti‐symmetric about the equator with centres in the region of the northeasterly and southwesterly trade winds. The positive GRAD (PGRAD) (negative GRAD [NGRAD]) modes defined by their northern or southern nodes are considered separately, as well as, if they are preceded or not by an El Niño (EN) (a La Niña, LN). The PGRAD mode defined by the northern (southern) node and preceded by an EN is indicated by PGRAD_TNA_EN (PGRAD_TSA_EN), and that not preceded by an EN is indicated by PGRAD_TNA (PGRAD_TSA). The corresponding NGRAD modes are indicated by NGRAD_TNA_LN, NGRAD_TSA_LN, NGRAD_TNA and NGRAD_TSA. Our analysis is limited to the NEB rainy season (March–May), when the GRAD mode is more pronounced and the NEB rainfall is more closely related to the TA SST variations. In general, the South Atlantic subtropical high is crucial in defining the cross‐equatorial flow, responsible for the anomalous meridional positioning of the Atlantic inter‐tropical convergence zone. When a positive (negative) dipole‐like SST anomaly pattern is established in the TA, the negative (positive) rainfall anomalies occupy most of NEB. This is the case of the PGRAD_TSA_EN, PGRAD_TNA, NGRAD_TSA_LN and NGRAD_TNA_LN. Most of the GRAD modes defined by TNA are also related to the El Niño‐Southern Oscillation (ENSO), in such a way that an EN (a LN) precedes a PGRAD (NGRAD) event, and most of the GRAD modes defined by TSA do not depend on the ENSO. Also, the PGRAD events are well distributed during both Atlantic multidecadal oscillation phases and the NGRAD events occur preferably during its cold phase.

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