SMOS and aquarius radiometers: inter-comparison over selected targets

• Published in: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing
• Main Authors: Pablos Hernández, Miriam, Piles Guillem, Maria, González Gambau, Veronica, Vall-Llossera Ferran, Mercedes Magdalena, Camps Carmona, Adriano José, Martinez, Justino
• Other Authors: Universitat Politècnica de Catalunya. Departament de Teoria del Senyal i Comunicacions, Universitat Politècnica de Catalunya. CTE-CRAE - Grup de Recerca en Ciències i Tecnologies de l'Espai, Universitat Politècnica de Catalunya. RSLAB - Grup de Recerca en Teledetecció
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2014
• Subjects: Àrees temàtiques de la UPC::Enginyeria de la telecomunicació::Radiocomunicació i exploració electromagnètica::Teledetecció; Àrees temàtiques de la UPC::Enginyeria civil::Geologia::Oceanografia; Soil moisture > Measurement; Remote sensing; Aquarius/Satelite de Aplicaciones Cientificas (SAC)-D mission; Brightness temperature; Inter-comparison; L-band radiometer; Passive microwave remote sensing; Soil Moisture and Ocean Salinity (SMOS) mission; Antarctica; Calibration; Instrument; Resolution; Salinity; Surface; Teledetecció; Sòls > Humitat > Mesurament; Antarc*
• Online Access: http://hdl.handle.net/2117/25154; https://doi.org/10.1109/JSTARS.2014.2321455

Passive microwave remote sensing at L-band is considered to be the most suitable technique to measure soil moisture and ocean salinity. These two variables are needed as inputs of predictive models, to improve climate and weather forecast, and to increase our knowledge of the water cycle. Nowadays, there are two space missions providing frequent and global observations of moisture and salinity of the Earth's surface with L-band radiometers on-board. The first one is the ESA's SMOS satellite, launched on November 2, 2009, which carries a two-dimensional, multi-angular, and full-polarimetric synthetic aperture radiometer. The second one is the NASA/CONAE's Aquarius/SAC-D mission, launched on June 10, 2011, which includes three beam push-broom real aperture radiometers. The objective of this work is to compare SMOS and Aquarius brightness temperatures and verify the continuity and consistency of the data over the entire dynamic range of observations. This is paramount if data from both radiometers are used for any long term enviromental, meteorological, hydrological, or climatological studies. The inter-comparison approach proposed is based on the study of 1 year of measurements over key target regions selected as representative of land, ice, and sea surfaces. The level of linearity, the correlation, and the differences between the observations of the two radiometers are analyzed. Results show a higher linear correlation between SMOS and Aquarius brightness temperatures over land than over sea. A seasonal effect and spatial inhomogeneities are observed over ice, at the Dome-C region. In all targets, better agreement is found in horizontal than in vertical polarization. Also, the correlation is higher at higher incidence angles. These differences indicate that there is a non-linear effect between the two instruments, not only a bias. Peer Reviewed Postprint (published version)