Soil moisture modelling of a SMOS pixel: interest of using the PERSIANN database over the Valencia Anchor StationReportar como inadecuado

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1 CESBIO - Centre d-études spatiales de la biosphère 2 UV - Facultat de Fisica València 3 CHRS - Center for Hydrometeorology and Remote Sensing

Abstract : In the framework of Soil Moisture and Ocean Salinity SMOS Calibration-Validation Cal-Val activities, this study addresses the use of the PERSIANN-CCS database in hydrological applications to accurately simulate a whole SMOS pixel by representing the spatial and temporal heterogeneity of the soil moisture fields over a wide area 50×50 km². The study focuses on the Valencia Anchor Station VAS experimental site, in Spain, which is one of the main SMOS Cal-Val sites in Europe. A faithful representation of the soil moisture distribution at SMOS pixel scale 50×50 km² requires an accurate estimation of the amount and temporal-spatial distribution of precipitation. To quantify the gain of using the comprehensive PERSIANN database instead of sparsely distributed rain gauge measurements, comparisons between in situ observations and satellite rainfall data are done both at point and areal scale. An overestimation of the satellite rainfall amounts is observed in most of the cases about 66% but the precipitation occurrences are in general retrieved about 67%. To simulate the high variability in space and time of surface soil moisture, a Soil Vegetation Atmosphere Transfer SVAT model – ISBA Interactions between Soil Biosphere Atmosphere is used. The interest of using satellite rainfall estimates as well as the influence that the precipitation events can induce on the modelling of the water content in the soil is depicted by a comparison between different soil moisture data. Point-like and spatialized simulated data using rain gauge observations or PERSIANN – CCS database as well as ground measurements are used. It is shown that a good adequacy is reached in most part of the year, the precipitation differences having less impact upon the simulated soil moisture. The behaviour of simulated surface soil moisture at SMOS scale is verified by the use of remote sensing data from the Advanced Microwave Scanning Radiometer on Earth observing System AMSR-E. We show that the PERSIANN database provides useful information at temporal and spatial scales in the context of soil moisture retrieval.

Autor: Silvia Juglea - Yann H. Kerr - Arnaud Mialon - Ernesto Lopez-Baeza - Dan Braithwaite - Kuolin Hsu -



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