Evaluation of Early Morning Heating Rate-derived Soil Moisture in Southern Europe

The soil moisture content is of great importance for numerical weather forecasts and has been identified as one of the parameter products of EUMETSAT’s Satellite Application Facility on Land Surface Analysis (Land SAF). Soil moisture strongly affects the surface energy balance and therefore near surface temperature and humidity. Conversely, temperature observations may be used to infer the soil moisture content. Since soil moisture fields are hardly available from in-situ measurements, the satellite-derived early morning surface temperature heating rate (dTs) might be used as an indirect signal for retrieving soil moisture information. The Tiled ECMWF Surface Scheme of Exchange processes at the Land surface (TESSEL) code is used to link the satellite derived early morning increase of surface temperature and soil moisture. Basically, it is intended to adjust the modelled soil moisture to match the satellite derived surface temperature difference. The model will be forced in the future by other Land SAF products (downwelling radiation, surface albedo and surface emissivity) and numerical weather prediction (NWP) analysis or forecast variables (air temperature, air humidity, wind speed). Additionally, site specific information on soil and vegetation types as well as Land SAF cloud and snow masks are needed. To test this approach, detailed field observations from several long term field campaigns in Europe and synoptic meteorological observations together with other forcing data are used in an ongoing study In this paper, first results are presented about the capability of the model to retrieve soil moisture from surface temperature measurements using detailed field observations collected during the MUREX campaign. The temperature-driven soil moisture data are compared with in-situ measurements of soil moisture, TESSEL model calculations, and soil moisture data derived from a spaceborne radar system the scatterometer on board of the European Remote Sensing Satellites ERS-1 and ERS-2. Scatterometer data are available on global scale and allow monitoring of regional soil moisture conditions (50 km scale). These data can also be derived from the Advanced Scatterometer (ASCAT) which will be flown on the EPS platform.