Abstract
Abstract. This study compares ERS scatterometer top soil moisture observations with simulations of a dual layer conceptual hydrologic model. The comparison is performed for 148 Austrian catchments in the period 1991–2000. On average, about 5 to 7 scatterometer images per month with a mean spatial coverage of about 37% are available. The results indicate that the agreement between the two top soil moisture estimates changes with the season and the weight given to the scatterometer in hydrologic model calibration. The hydrologic model generally simulates larger top soil moisture values than are observed by the scatterometer. The differences tend to be smaller for lower altitudes and the winter season. The average correlation between the two estimates is more than 0.5 in the period from July to October, and about 0.2 in the winter months, depending on the period and calibration setting. Using both ERS scatterometer based soil moisture and runoff for model calibration provides more robust model parameters than using either of these two sources of information.
Highlights
Continuous progress in the remote sensing technology and advances in the retrieval and mapping concepts go in line with the efforts of testing their accuracy and applicability in different fields and disciplines
The hydrologic model simulates the soil moisture from observed daily air temperature and precipitation using model parameters, which need to be estimated by the calibration
The relative top soil moisture is obtained by relating the amount of water stored in the top soil layer to a model parameter Lskin which defines the maximum capacity of that reservoir
Summary
Continuous progress in the remote sensing technology and advances in the retrieval and mapping concepts go in line with the efforts of testing their accuracy and applicability in different fields and disciplines. Due to its indirect way of retrieval and a coarse spatial resolution, the validation and comparison with other soil moisture estimates over different scales and regions is needed. In a more extensive comparison, Ceballos et al (2005) validated scatterometer observations with field measurements from the REMEDHUS soil moisture station network (20 stations) in the central part of the Duero Basin located in West Spain. In this area they found mean square error between the scatterometer data and the average soil moisture in the 0–100 cm profile of 2.2 vol % and the coefficient of determination of 0.75. Several similar experiments have shown beneficial information of SCAT soil moisture data in hydrological (Dirmeyer et al, 2004; Scipal et al, 2005; Parajka et al, 2005; Pellarin et al, 2006), Published by Copernicus Publications on behalf of the European Geosciences Union
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