DESENVOLVIMENTO DE ALGORITMOS OPERACIONAIS PARA A DETERMINAÇÃO DE PARÂMETROS À SUPERFÍCIE DO SOLO COM BASE NOS SISTEMAS MSG E EPS: UMA APROXIMAÇÃO FÍSICA INTEGRADA

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Improving the retrieval of downwelling surface shortwave fluxes using data from geostationary satellites

Publication . Maria, Dulce Filomena Lajas,1972-; Câmara,Carlos Portugal da,1957-

Shortwave radiation is a key quantity to estimate the surface radiation budget which has a close relationship with the climate of a given region. Shortwave radiation is affected by aerosols and clouds. Aerosols modify the Earth’s radiation budget and boundary layer meteorology by reflecting sunlight to space and absorbing radiation in the atmosphere. Clouds modulate the vertical and horizontal distributions of solar radiative heating, latent heat, and cooling by thermal radiation that drive the atmospheric circulation. The main objective of this thesis is to analyze in detail the methodology presently used to derive the Downwelling Surface Shortwave Flux (DSSF) based on information from geostationary satellites. The study is closely related to operational activities developed within the framework of the Satellite Application Facility on Land Surface Analysis (LSA SAF). An already existing operational DSSF algorithm, developed within the framework of the Ocean and Sea Ice (O&SI) SAF, is tested and improved for clear and cloudy sky conditions. In the case of clear sky, the parameterisation for atmospheric absorption accounts for the variation of the concentration of the atmospheric components. In the case of cloudy sky, radiation interactions are more complex and, besides the interaction with the atmosphere, the parameterisation scheme accounts for cloud albedo and relies on a predefined value characterizing the absorption by clouds. Both methodologies are analyzed and two parameterizations are proposed; for cloudy sky pixels the new parameterisation takes cloud types into account whereas, in the clear sky case, diffuse radiation is explicitly included in the DSSF model, based on information about aerosol optical thickness. Model performance is significantly improved and for both methodologies an approach to their integration in an operational environment is proposed.

2012Tese de doutoramento

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Fundação para a Ciência e a Tecnologia

Número da atribuição

SFRH/BD/2769/2000