Cross calibration and synergistic applications of SMOS with derived surface moisture and texture obtained from multi-frequency satellite radar altimetry and in-situ data

ESA's Forthcoming Soil Moisture and Ocean Salinity (SMOS) mission has been designed to observe soil moisture over the Earth's landmasses and salinity over the oceans. Soil moisture data are urgently required for hydrological studies and data on ocean salinity are vital for improving our understanding of ocean circulation patterns.

The sensitivity of radar altimeters to surface soil moisture is being exploited synergistically

with GRACE data, the AussieGRASS project and various ground campaigns in order to provide estimates of surface moisture for comparison with values derived from SMOS.

This project makes use of the recent development of a semi-empirical model for altimeter derived measurements of soil surface moisture over arid and semi-arid terrain permits estimates of moisture within the top few centimeters to be generated from EnviSat and Jason-1 data.

This development, together with empirically based and detailed surface sigma0 (σ⁰) models at Ku band over Africa, Australia and parts of the Middle East now permits three contributions to the SMOS mission:

in conjunction with campaigns of opportunity, to take the detailed measurements over campaign sites and extend these along arcs of altimeter data to provide precise estimates on a spatial scale commensurate with SMOS pixels;
to generate altimeter derived estimates of soil moisture in desert regions on a global scale for direct comparison with SMOS data;
by comparing the detailed altimeter sigma0 (σ⁰) models with SMOS data and auxiliary information, to mine the SMOS dataset for additional geophysical information.

The whole of Australia is to be used as a calibration/validation (CAL/VAL) area and to explore the geophysical information contained in the SMOS data. Synergy with the GRACE mission will be exploited using test areas where altimeter measurements of surface water have been combined with GRACE estimates of total hydrological signal; the missing component of soil moisture can be contributed from SMOS and combined with available profiles of soil surface moisture generated from altimetry. This synergy will be assessed using the Okavango Delta, a unique environment where the internal delta results in a huge hydrological signal, well seen in altimeter derived soil moisture estimates.