Modelling the passive microwave signature from land surfaces: a review of recent results and application to the SMOS & SMAP soil moisture retrieval algorithms

Authors: WIGNERON, J. - National Agricultural Research Foundation (NAGREF); Jackson, Thomas; O'NEILL, PEGGY - Goddard Space Flight Center; DE JEU, R.A.M - Bennekom, The Netherlands; DE ROSNAY, P. - European Centre For Medium-Range Weather Forecasts (ECMWF); WALKER, J. - Monash University; FERRAZOLI, P. - University Of Rome; MIRNOV, V. - Collaborator; BIRCHER, S. - Center For The Study Of The Biosphère From Space(CESBIO); GRANT, J. - Lund University; KURUM, M. - Goddard Space Flight Center; SCHWANK, M - Swiss Federal Research Institute Wsl; LEVINE, D - Goddard Space Flight Center; DAS, N. - Jet Propulsion Laboratory; ROYER, A. - Universite De Sherbrooke; AL-YARRI, A. - National Institute For Agricultural Research (INIAP); BITAR, A. - University Of Toulouse; FERNANDEZ-MORAN, R. - National Institute For Agricultural Research (INIAP); LAWRENCE, H. - European Centre For Medium-Range Weather Forecasts (ECMWF); MIALON, A. - University Of Toulouse

Submitted to: Remote Sensing of Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2017
Publication Date: 4/1/2017
Publication URL: http://handle.nal.usda.gov/10113/5631936
Citation: Wigneron, J., Jackson, T.J., O'Neill, P., De Jeu, R., De Rosnay, P., Walker, J., Ferrazoli, P., Mirnov, V., Bircher, S., Grant, J., Kurum, M., Schwank, M., Levine, D., Das, N., Royer, A., Al-Yarri, A., Bitar, A., Fernandez-Moran, R., Lawrence, H., Mialon, A. 2017. Modelling the passive microwave signature from land surfaces: a review of recent results and application to the SMOS & SMAP soil moisture retrieval algorithms. Remote Sensing of Environment. 192:238-262.

Interpretive Summary: The most significant advances in modelling the passive microwave emission from land surfaces over the past decade were identified and critical needs for improvement were identified. These advances have been due primarily to the intensive research conducted to support the two dedicated soil moisture remote sensing satellites; the Soil Moisture Ocean Salinity and Soil Moisture Active Passive missions launched in 2009 and 2015 respectively. This research has moved several components from semi-empirical to physically based approaches; specifically soil roughness, vegetation scattering, and linking vegetation indices and vegetation optical thickness. These results obtained provide very useful insights for further development and improvement of soil moisture retrieval algorithms that will lead to more reliable and robust products for agricultural hydrology.

Technical Abstract: Two passive microwave missions are currently operating at L-band to monitor surface soil moisture (SM) over continental surfaces. The SMOS sensor, based on an innovative interferometric technology enabling multi-angular signatures of surfaces to be measured, was launched in November 2009. Recently, the SMAP sensor, based on a large mesh reflector 6 meters in diameter providing a conically scanning antenna beam with a surface incidence angle of 40°, was launched in January of 2015. Over the last decade, an intense scientific activity has focused on the development of the SM retrieval algorithms for the two missions. This activity has relied on many field (mainly tower-based) and airborne experimental campaigns, and since 2010-2011, on the SMOS and Aquarius space-borne L-band observations. It has relied too on the use of numerical, physical and semi-empirical models to simulate the microwave brightness temperature of natural scenes for a variety of scenarios in terms of system configurations (polarization, incidence angle) and soil, vegetation and climate conditions. Key components of the inversion models have been evaluated and new parameterizations of the effects of the surface temperature, soil roughness, soil permittivity, and vegetation extinction and scattering have been developed. Among others, global maps of select radiative transfer parameters have been estimated very recently. Based on this intense activity, improvements of the SMOS and SMAP SM inversion algorithms have been proposed. Some of them have already been implemented while others are currently being investigated. In this paper, we present a review of the significant progress which has been made over the last decade in this field of research with a focus on L-band, and a discussion on possible applications to the SMOS and SMAP soil moisture retrieval approaches.