Basin scale rainfall-evapotranspiration dynamics in a tropical semiarid environment during dry and wet years |
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| Institution: | 1. Climate Sciences Program, Federal University of Rio Grande do Norte (UFRN), Natal, Rio Grande do Norte, Brazil;2. Executive Agency of Water Management of the Paraíba State, Campina Grande, Paraíba, Brazil;3. National Institute of the Semiarid (INSA), Campina Grande, Paraíba, Brazil;4. COSTEL LETG, UMR 6554 CNRS, University of Rennes 2, Rennes, Bretagne, France;5. Department of Atmospheric and Climate Sciences, Federal University of Rio Grande do Norte (UFRN), Natal, Rio Grande do Norte, Brazil;1. Campus Sobral, Federal Institute of Education, Science and Technology of Ceará — IFCE, Sobral, Av. Dr. Guarani, 317, Derby Clube, 62042-030, Brazil;2. Department of Agricultural Engineering, Federal University of Ceará — UFC, Fortaleza 60356-000, Brazil;1. Department of Agricultural Engineering, Federal University of Viçosa (UFV), Avenue Peter Henry Rolfs, Viçosa, MG, 36570-900, Brazil;2. Embrapa Tabuleiros Costeiros, Avenue Beira Mar, 3250 - Jardins, Aracaju, SE, 49040-490, Brazil;1. Key Laboratory for Agricultural Soil and Water Engineering in Arid Area of Ministry of Education, Northwest A&F University, Yangling, Shaanxi 712100, PR China;2. Institute of Water Saving Agriculture in Arid Regions of China, Northwest A&F University, Yangling, Shaanxi 712100, PR China |
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| Abstract: | In semiarid regions the occurrence of alternating long drought and heavy rainfall periods directly impacts water availability, affecting human water supply, agriculture development and the provision of ecosystem services. Because of that, research on the water input and output fluxes at the basin scale is of paramount importance. In this sense, rainfall-evapotranspiration (ET) dynamics play a critical role in water, soil and vegetation interactions, in hydrometeorological modelling and in the energy fluxes dynamics of semiarid regions. Therefore, the objective of this study was to quantify daily ET during a wet year and a dry year in a watershed located in the Brazilian Semiarid, by using remote sensing data and formulations based on the Simplified Surface Energy Balance Index (S-SEBI) and the Simplified Surface Energy Balance (SSEB) algorithms. Land surface temperature, albedo and NDVI data from MODIS sensor and solar radiation data from weather stations located in the basin were used. Rainfall analysis indicated 2009 and 2012 as being representatives of anomalously wet and dry years respectively, which were selected for the quantification of ET. The proposed algorithm was adjusted and verified with data from a flux tower equipped with eddy covariance system. Daily remote sensing ET estimates showed good agreement with observed values (RMSE = 0.79 mm.d?1) and the annual ET relative error was of 7.7% (35.4 mm.year?1). Results showed that the native vegetation can delay its dormant state for five months during wet years. During the wet year, ET differences between land cover classes were less noticeable due to soil saturation and the urgency of vegetated surfaces to meet their physiological needs. In dry year, however, differences were more evident, with bare soil presenting lower ET rates and vegetation classes showing higher ET values. |
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| Keywords: | Remote sensing ET SSEB S-SEBI Eddy covariance Caatinga Seasonally dry tropical forest MODIS |
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