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The objective of this study was to evaluate the annual standardized precipitation index (SPI) obtained from the DrinC software based on multivariate analysis in the identification of rainfall and drought extremes in the State of Alagoas and its relationship with El Niño-Southern Oscillation. Monthly rainfall data from 1960 to 2016 from National Water Agency were analysed. Annual SPI (SPI-12) has been designed for comparison with ENSO phases via Oceanic Niño Index for 3.4 region and in identifying climate extremes in the State of Alagoas. The principal component analysis and cluster analysis techniques were applied to the rainfall series of SPI-12. Extreme events were identified in both rainy and drought periods according to SPI-12, and were associated with the ENSO phases (El Niño, La Niña, and Neutral). The first four principal components explained 46.68% of the variance. Our findings are crucial for agriculture and civil defence since northeastern Brazil has several areas of risk and social vulnerability.

A B S T R A C TThe effects of the forage cactus sorghum configuration and different irrigation depths on the growth, water use and efficiency of the forage cactus production system were investigated in this study. The experiment was conducted in the municipality of Serra Talhada, Pernambuco State, Brazil, between the years 2012 and 2013. Forage cactus was distributed in randomized blocks with factorial scheme and four replicates, in split plots (5 x 2), with five irrigation depths (0, 8.75, 17.5, 26.25 and 35% of the reference evapotranspiration, ET 0 ) and two cropping systems (forage cactus monocropping and forage cactus sorghum intercropping). Crop evapotranspiration was calculated through soil water balance. The ratio between crop and reference evapotranspiration, and land use and water use efficiencies, were estimated. Irrigation depths and the intercropping affected only forage cactus canopy width and cladode biomass. The ratio between crop and reference evapotranspiration increased with the increase of irrigation depths, while the highest water use efficiency based on dry matter occurred at irrigation depths higher than 1,096 mm year -1 in the intercropping (21.8 ± 6.8 kg ha -1 mm -1 ). Irrigation depths did not affect land use efficiency (0.83). Water depths from 1,096 to 1,202 mm year -1 are recommended in the forage cactus sorghum system. Crescimento, consumo de água e eficiência do consórcio palma-sorgo sob diferentes lâminas de água R E S U M OOs efeitos da configuração palma-sorgo e de diferentes lâminas de irrigação sobre o crescimento, consumo de água e eficiência do sistema de produção da palma foram investigados neste estudo. O experimento foi conduzido em Serra Talhada, PE, entre os anos de 2012 e 2013, com a palma disposta em blocos ao acaso, quatro repetições, em parcelas subdivididas (5 x 2) de cinco lâminas (0, 8,75, 17,5, 26,25 e 35% da evapotranspiração de referência) e dois sistemas de cultivo (palma exclusiva e consórcio palma-sorgo). A evapotranspiração real da cultura foi calculada por meio do balanço de água no solo. Estimou-se a razão evapotranspiração real e de referência, além das eficiências do uso da água e da terra. As lâminas de irrigação e a adoção do consórcio afetaram apenas a largura do dossel e a biomassa dos cladódios da palma forrageira. A razão evapotranspiração real e de referência aumentou com o incremento da lâmina de irrigação, enquanto as maiores eficiências do uso da água com base na massa seca ocorreram nas lâminas de água superiores a 1.096 mm ano -1 no consórcio (21,8 ± 6,8 kg ha -1 mm -1 ). As lâminas de irrigação não afetaram a eficiência do uso da terra (0,83). No sistema palma-sorgo, recomendam-se lâminas de água entre 1.096 e 1.202 mm ano -1 .

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Caatinga biome, located in the Brazilian semi-arid region, is the most populous semi-arid region in the world, causing intensification in land degradation and loss of biodiversity over time. The main objective of this paper is to determine and analyze the changes in land cover and use, over time, on the biophysical parameters in the Caatinga biome in the semi-arid region of Brazil using remote sensing. Landsat-8 images were used, along with the Surface Energy Balance Algorithm for Land (SEBAL) in the Google Earth Engine platform, from 2013 to 2019, through spatiotemporal modeling of vegetation indices, i.e., leaf area index (LAI) and vegetation cover (VC). Moreover, land surface temperature (LST) and actual evapotranspiration (ETa) in Petrolina, the semi-arid region of Brazil, was used. The principal component analysis was used to select descriptive variables and multiple regression analysis to predict ETa. The results indicated significant effects of land use and land cover changes on energy balances over time. In 2013, 70.2% of the study area was composed of Caatinga, while the lowest percentages were identified in 2015 (67.8%) and 2017 (68.7%). Rainfall records in 2013 ranged from 270 to 480 mm, with values higher than 410 mm in 46.5% of the study area, concentrated in the northern part of the municipality. On the other hand, in 2017 the lowest annual rainfall values (from 200 to 340 mm) occurred. Low vegetation cover rate was observed by LAI and VC values, with a range of 0 to 25% vegetation cover in 52.3% of the area, which exposes the effects of the dry season on vegetation. The highest LST was mainly found in urban areas and/or exposed soil. In 2013, 40.5% of the region’s area had LST between 48.0 and 52.0 °C, raising ETa rates (~4.7 mm day−1). Our model has shown good outcomes in terms of accuracy and concordance (coefficient of determination = 0.98, root mean square error = 0.498, and Lin’s concordance correlation coefficient = 0.907). The significant increase in agricultural areas has resulted in the progressive reduction of the Caatinga biome. Therefore, mitigation and sustainable planning is vital to decrease the impacts of anthropic actions.

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