Operational tools and applications of EO satellite data to retrieve surface fluxes in semi-arid countries

Abstract

The overall objective of the thesis is to develop and evaluate useful tools and applications of Earth Observation (EO) satellite data to estimate surface fluxes in semiarid countries. The first specific objective (Chapter 4) is to assess the performance and robustness of the triangle method, a remote sensing (RS) based method to retrieve and map land evapotranspiration (ET). Emphasis is put on the estimation of soil heat flux (G), which represents an important sink of energy in these regions. Estimating accurately G is still very problematic, because of its dependence on both vegetation cover fraction and soil physical properties. To that aim, the partial goals are: - Proposal of a new parameterisation scheme for G, based on a linear relationship with the evaporative fraction (EF) - Assessment of the ET retrieval triangle method with the new Gparameterisation As a second specific objective (Chapter 5), the triangle method was compared with predictions supplied by a land surface model (JULES) with the purpose of illustrating how these two different approaches can be combined to improve the estimations of surface fluxes. The third objective is to demonstrate the potential of RS-based information for actual operational applications related to the monitoring of surface fluxes in semi-arid countries (Chapter 6). The first one is the application of the triangle method to obtain maps of actual ET in western Africa. The second one is the application of the same method to analyse the annual evolution of surface energy balance (SEB) components and to study drought climatology over a 12-year period in the Segura river basin in South-East Spain. The third is the use of sea surface temperature (SST) coupled to an energy balance model of a water body to characterise the thermal behaviour of coastal lagoon (Mar Menor) located in South-East Spain.