Analysis of roughness effects based in-situ ELBARA-II and spaceborne SMOS observations over the vas (Valencia Anchor Station)

The European Space Agency (ESA) Soil Moisture and Ocean Salinity mission (SMOS), was launched in November 2009. The payload for the mission was the Microwave Imaging Radiometer using Aperture Synthesis [1, 2]. Since the launch, global maps of brightness temperatures (T_B) at L-band have been available. Angular characteristics of T_B for horizontal and vertical polarization are used for the simultaneous retrieval of surface soil moisture (SM) and vegetation optical depth (TAU). Ground based radiometers such as the ELBARA-II radiometer [3] at the Valencia Anchor Station (VAS) are playing a key role in Calibration/Validation activities for this mission [4]. The L-band Microwave of the Emission of Biosphere model (L-MEB) is used to obtain level 2 products (SM, TAU) from T_B measured by SMOS [5]. It is important to first test all suggested improvements to L-MEB on ground-based data before implementing them into the SMOS algorithm. In this study, time series of radiometer measurements covering two vine vegetation periods were used to evaluate recent studies regarding L-MEB model with respect to this crop so significant and representative in many regions of the world. A good correlation between radiometer and SMOS T_B was found (0.8). For the level 2 products, the correlation was less pronounced and varied with surface conditions and type of the orbit.