Adjusting a simple crop model to predict maize and sorghum yield in the northeast Brazil.

A agricultura de sequeiro no Nordeste do Brasil tem sido frequentemente afetada pelas condições adversas de tempo e clima. Para antecipar a ocorrência de um colapso na produção agrícola o presente trabalho objetivou ajustar um modelo agrometeorológico para as culturas de milho e sorgo nos municípios de Serra Talhada e Araripina, ambos no estado de Pernambuco. Foi utilizado o modelo de balanço hídrico do CPTEC/INPE, incluindo informações para estimar colapso de safra, como proposto por Doorenbos e Kassan (1979). A análise apresentou um índice de concordância de 80%, classificado como muito bom, e um erro menor que 30%, classificado como aceitável, o que sugere que o modelo ajustado possa também produzir estimativas satisfatórias pra toda região Nordeste

Tools for communicating agricultural drought over the Brazilian Semiarid using the soil moisture index

Soil moisture over the Brazilian semiarid region is presented in different visualizations that highlight spatial, temporal and short-term agricultural risk. The analysis used the Soil Moisture Index (SMI), which is based on a normalization of soil moisture by field capacity and wilting point. The index was used to characterize the actual soil moisture conditions into categories from severe drought to very wet. In addition, the temporal evolution of SMI was implemented to visualize recent trends in short-term drought and response to rainfall events at daily time steps, as new data are available. Finally, a visualization of drought risk was developed by considering a critical value of SMI (assumed as 0.4), below which water stress is expected to be triggered in plants. A novel index based on continuous exposure to critical SMI was developed to help bring awareness of real time risk of water stress over the region: the Index of Stress in Agriculture (ISA). The index was tested during a drought over the region and successfully identified locations under water stress for periods of three days or more. The monitoring tools presented here help to describe the real time conditions of drought over the region using daily observations. The information from those tools support decisions on agricultural management such as planting dates, triggering of irrigation, or harvesting.Peer ReviewedPostprint (published version

Use of SMOS L3 soil moisture data: validation and drought assessment for Pernambuco State, Northeast Brazil

The goal of this study was to validate soil moisture data from Soil Moisture Ocean Salinity (SMOS) using two in situ databases for Pernambuco State, located in Northeast Brazil. The validation process involved two approaches, pixel-station comparison and areal average, for three regions in Pernambuco with different climatic characteristics. After validation, the SMOS data were used for drought assessment by calculating soil moisture anomalies for the available period of data. Four statistical criteria were used to verify the quality of the satellite data: Pearson correlation coefficient, Willmott index of agreement, BIAS, and root mean squared difference (RMSD). The average RMSD calculated from the daily time series in the pixel and the areal assessment were 0.071 m3m-3 and 0.04 m3m-3, respectively. Those values are near to the expected 0.04 m3m-3 accuracy of the SMOS mission. The analysis of soil moisture anomalies enabled the assessment of the dry period between 2012 and 2017 and the identification of regions most impacted by the drought. The driest year for all regions was 2012, when the anomaly values achieved -50% in some regions. The use of SMOS data provided additional information that was used in conjunction with the precipitation data to assess drought periods. This may be particularly relevant for planning in agriculture and supporting decision makers and farmers.Peer ReviewedPostprint (published version

Trocas de energia e fluxo de carbono entre a vegetação de caatinga e atmosfera no Nordeste brasileiro.

Neste estudo foram avaliadas as variações sazonais dos fluxos de dióxido de carbono, de vapor de água e de energia em área de caatinga nativa, no nordeste do Brasil. A taxa de evapotranspiração (LE) do sistema é muito baixa tanto na estação seca quanto na estação chuvosa devido à baixa disponibilidade de água na região, com valores próximos de zero no final da estação seca. Durante a estação seca, cerca de 60 % da energia disponível (Rn) foi utilizada para aquecer o ar (H) e LE correspondeu a 10% de Rn, em média. Durante a estação chuvosa essas taxas foram, respectivamente, 46 e 17%. Quanto ao fluxo de CO2, o ecossistema atua como sumidouro de CcO2 no início da estação seca, quando o solo ainda contém umidade decorrente da estação chuvosa anterior, bem como na estação chuvosa. Já no final da estação seca, quando os estômatos se fecham e há uma redução significativa no folhedo em função do déficit hídrico, a taxa de fotossíntese torna-se nula e o sistema passa a atuar como fonte de CcO2

Remote Sensing as a Tool for Agricultural Drought Alert Over the South Region of Brazil

In this study the estimative of the Combined Drought Index (CDI) to identify agricultural drought over Southern Brazil is introduced. This combined drought index is based on a combination of three indicators: Standardized Precipitation Index (SPI), Soil Moisture Anomalies (SMA) and Vegetation Health Index (VHI). The proposed CDI has four levels, watch, warning, alert I and alert II, thus benefiting an increasing degrees of severity. This CDI was applied during the first 6 months of 2020 to different study sites over Southern Brasil, representative of the crop areas. The performance of the CDI levels was assessed by comparison with risk areas. Observations show a good match between these areas and the CDI. Important crop drought events in 2020 were correctly predicted by the proposed CDI in all areas

Impact of soil moisture on crop yields over Brazilian semiarid

The objective of this work was to investigate the relationship between soil water content and rainfall with rice, beans, cassava and corn yields in the semiarid region of Northeast Brazil. Precipitation and modeled soil water content were compared to yields recorded at the county levels in this region. The results were also integrated over the area of the nine States that lie within the officially recognized region of semiarid climate in Brazil. The influence of water balance components was quantified by calculating their correlation coefficient with yields of the different crop species over the municipalities of the region. It was found that rainfall had higher correlation to crop yields over most of the region, while soil water content had lower values of correlation. This result is consistent with the fact that average root depth is 40 cm, lower than the layer of soil used in the model used to estimate soil water content (100 cm). Plants respond better to the precipitation in the top layers of soil, while the water storage in the deep layer of soil might be important only in other temporal and spatial scales of the hydrological cycle.Peer ReviewedPostprint (published version

Desenvolvimento de Metodologia para Validação e Análise de dados de dióxido de enxofre (so2) Atmosférico sobre o Continente Sul-Americano

This work describes the development of a methodology for validating the use of Brewer spectrophotometer for measuring the SO2 total columns, from adaptations in its original calculation algorithm. The results obtained show the possibility of using Brewer spectrophotometer to measure the total columns of sulfur dioxide, with a gain in data quality, of great help to understand the behavior of this gas in the atmosphere with observations that can be used for model validation and calibration of satellites.Este trabalho mostra o desenvolvimento de uma metodologia para validar o uso do espectrofotômetro Brewer na medição das colunas totais de SO2, a partir de adaptações em seu algoritmo original de cálculo. Os resultados obtidos revelam a possibilidade de uso do espectrofotômetro Brewer para medir as colunas totais de dióxido de enxofre, com ganho na qualidade dos dados, de grande auxílio para o conhecimento do comportamento deste gás na atmosfera, com observações que podem ser utilizadas para validação de modelos e calibração de satélites