Visiting Scientists

Cornélio Alberto Zolin

Associated Labex Scientist: Carlos Eduardo Lazarini da Fonseca

Satellite-based monitoring of drought and water use over Brazil

Research Team: Cornélio Alberto Zolin - Researcher at Embrapa Agrosilvopastoral, Sinop/MT, William P. Kustas and Martha Anderson - Researchers at USDA/ARS, Hydrology and Remote Sensing Lab (HRSL), Beltsville/MD, Eduardo Delgado Assad - Researcher at Embrapa Informatics, Campinas/SP

 Objectives: Evaluate and implement a physically-based model, developed by HRSL scientists, to monitoring drought and water use at continental and regional scale over Brazil, employing thermal imagery from geostationary satellites and using surface temperature as a proxy for soil moisture to map actual daily evapotranspiration (ET), needing no precipitation data.

Approach: Surface temperature maps derived from the thermal waveband contain valuable information for detecting moisture stress conditions.  Soil surface and vegetation canopy temperatures rise as soil moisture in the surface layer and root zone is depleted, with thermal stress signals typically preceding significant reduction in biomass. Estimates of current water use by agriculture and native/natural vegetation that can be mapped at regional scales is paramount in understanding how changes in future climate and hence water availability may affect crop productivity and yield, and ecosystem health in different regions.

Results: A new satellite-based water use and drought index, using surface temperature as a proxy for soil moisture, has been successfully evaluated over the U.S. and could provide valuable information for water management in data-sparse regions, specifically in Brazil. A derived Evaporative Stress Index (ESI), relating actual to potential evapotranspiration (ET/PET), has been shown a good agreement with standard precipitation-based drought indices over US. A thermal-based remote sensing system for routine monitoring of drought and consumptive water use (ET) will be validated over the various agricultural and native/natural ecosystems in the different climatic regions of Brazil.  A robust water use and drought early warning system is essential for adaptive agricultural management under changing climatic conditions, and for providing a reliable indicator of weather/climate related impacts on crop yield, ecosystem health and water availability at regional scales.  An intercomparison of the physically-based ET and ESI products with other ET products and drought indices currently used in Brazil will establish strengths and weaknesses of current approaches and identify areas needing further study and validation.