Study of salinity retrieval errors for the SMOS mission

Memoria de tesis doctoral presentada por Carolina Gabarró Prats para obtener el título de Doctora por la Universitat Politècnica de Catalunya (UPC), realizada bajo la dirección del Dr. Jordi Font Ferré del Institut de Ciències del Mar (ICM-CSIC) y del Dr. Adriano Camps Carmona.-- 201 pages[CAT] El treball realitzat en aquesta tesi està emmarcat en la missió SMOS (Soil Moisture and Ocean Salinity) de l’Agència Espacial Europea. El satèl•lit es llançarà el febrer del 2007, i mesurarà la salinitat superficial del mar i la humitat del sòl. L’instrument (MIRAS) consisteix en un radiòmetre interferomètric en banda L (1,400-1,430 GHz). Serà la primera vegada que es posarà en òrbita un instrument d’aquestes característiques i que es mesuraran aquests paràmetres des de l’espai. No obstant, encara son molts els aspectes científics que queden per resoldre. Aquesta tesi, doncs, ha intentat abordar alguns del temes oberts en la recuperació de la salinitat a partir de les mesures de SMOS. [...][EN] This PhD thesis has been done in the framework of the SMOS (Soil Moisture and Ocean Salinity) mission, from the European Space Agency. This satellite will be launched in February 2007 and will provide global sea surface salinity and soil moisture maps, variables that never have been measured before from space. The payload instrument (MIRAS) is an L-band interferometric radiometer. This will be the first time an instrument with this characteristics is put in orbit. However, there are still a lot of issues that need to be solved. This thesis is focused on some open questions of the salinity retrieval process from SMOS measurements. [...]Peer reviewe

CAROLS: A New Airborne L-Band Radiometer for Ocean Surface and Land Observations

The “Cooperative Airborne Radiometer for Ocean and Land Studies” (CAROLS) L-Band radiometer was designed and built as a copy of the EMIRAD II radiometer constructed by the Technical University of Denmark team. It is a fully polarimetric and direct sampling correlation radiometer. It is installed on board a dedicated French ATR42 research aircraft, in conjunction with other airborne instruments (C-Band scatterometer—STORM, the GOLD-RTR GPS system, the infrared CIMEL radiometer and a visible wavelength camera). Following initial laboratory qualifications, three airborne campaigns involving 21 flights were carried out over South West France, the Valencia site and the Bay of Biscay (Atlantic Ocean) in 2007, 2008 and 2009, in coordination with in situ field campaigns. In order to validate the CAROLS data, various aircraft flight patterns and maneuvers were implemented, including straight horizontal flights, circular flights, wing and nose wags over the ocean. Analysis of the first two campaigns in 2007 and 2008 leads us to improve the CAROLS radiometer regarding isolation between channels and filter bandwidth. After implementation of these improvements, results show that the instrument is conforming to specification and is a useful tool for Soil Moisture and Ocean Salinity (SMOS) satellite validation as well as for specific studies on surface soil moisture or ocean salinity

The AACES field experiments: SMOS calibration and validation across the Murrumbidgee River catchment

Following the launch of the European Space Agency's Soil Moisture and Ocean Salinity (SMOS) mission on 2 November 2009, SMOS soil moisture products need to be rigorously validated at the satellite's approximately 45 km scale and disaggregation techniques for producing maps with finer resolutions tested. The Australian Airborne Cal/val Experiments for SMOS (AACES) provide the basis for one of the most comprehensive assessments of SMOS data world-wide by covering a range of topographic, climatic and land surface variability within an approximately 500 × 100 km<sup>2</sup> study area, located in South-East Australia. The AACES calibration and validation activities consisted of two extensive field experiments which were undertaken across the Murrumbidgee River catchment during the Australian summer and winter season of 2010, respectively. The datasets include airborne L-band brightness temperature, thermal infrared and multi-spectral observations at 1 km resolution, as well as extensive ground measurements of near-surface soil moisture and ancillary data, such as soil temperature, soil texture, surface roughness, vegetation water content, dew amount, leaf area index and spectral characteristics of the vegetation. This paper explains the design and data collection strategy of the airborne and ground component of the two AACES campaigns and presents a preliminary analysis of the field measurements including the application and performance of the SMOS core retrieval model on the diverse land surface conditions captured by the experiments. The data described in this paper are publicly available from the website: <a href="http://www.moisturemap.monash.edu.au/aaces"target="_blank">http://www.moisturemap.monash.edu.au/aaces</a>

Aquarius and Remote Sensing of Sea Surface Salinity from Space

Aquarius is an L-band radiometer and scatterometer instrument combination designed to map the salinity field at the surface of the ocean from space. The instrument is designed to provide global salinity maps on a monthly basis with a spatial resolution of 150 km and an accuracy of 0.2 psu. The science objective is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean. This data will promote understanding of ocean circulation and its role in the global water cycle and climate

Assimilation des données SMOS dans un modèle des surfaces continentales : mise en œuvre et évaluation sur la France

Assimiler l'humidité superficielle du sol (SSM) dans un modèle de surface améliore la modélisation du contenu en eau du sol. La télédétection est un outils indispensable pour suivre l'évolution de cette variable. SMOS, lancé en Novembre 2009, est le premier satellite dédié à l'étude de l'humidité du sol. Les premières données SMOS ont été comparées aux données ASCAT sur la France. Les données ASCAT se corrèlent mieux aux observations in situ et aux SSM simulées que les données SMOS pendant l'année 2010. Sur le sol nu du site de SMOSREX (2003-2005), les SSM mesurés ont été assimilées dans une nouvelle version multi-couches du modèle Interaction entre le Sol, la Biosphère et l'Atmosphère (ISBA). Un Filtre de Kalman Etendu Simplifié (SEKF) a été utilisé pour analyser le profil d'eau du sol dans les 11 couches de la version multi-couches du modèle de surface (ISBA-DF). Pendant les périodes sèches, les corrections impactent les 15 premiers centimètres du sol alors que pendant les périodes humides, des corrections moins intenses affectent l'ensemble de la colonne de sol. Afin de préparer l'assimilation des températures de brillance (TB), des TB ont été simulées par couplage entre ISBA-DF et un modèle d'émission micro-ondes (CMEM). Avec ISBA-DF, il est préférable de modéliser les TB en utilisant l'approche de Wilheit pour le calcul de l'émissivité de surface lisse et de prendre en compte l'impact des variations de SSM dans le calcul de la rugosité. Finalement, les TB de SMOSREX ont été assimilées dans ISBA-DF. Considérer CMEM comme opérateur d'observations dans le SEKF permet d'obtenir un état analysé proche de celui obtenu lors de l'assimilation des SSM dans ISBA-DF.Assimilating surface soil moisture (SSM) in a land surface model permits a better monitoring of the soil water content. Remote sensing is an indispensable tool for monitoring the evolution of SSM, both spatially and temporally. SMOS was launched in November 2009 and it is the first satellite specifically dedicated to SSM mapping over continents. A comparison of the first SMOS data with ASCAT over France showed that the ASCAT product was better correlated with in situ SSM observations and with SSM simulations for the year 2010. Over bare soil plot of SMOSREX (2003-2005), in situ SSM were assimilated into a new multi-layer version of the soil module of the Interaction between the Soil, Biosphere, Atmosphere (ISBA) land surface model. A simplified Extended Kalman Filter was used to analyze 11 soil layers of the ISBA multi-layer version (ISBA-DF). For dry periods, corrections affected a shallow 0-15 cm top soil layer. For wet period, weaker corrections were applied for the entire column. To prepare the assimilation of the TB, the TB were produced by coupling ISBA-DF with a microwave emission model (CMEM). With ISBA-DF, computing TB using the Wilheit smooth surface emissivity and taking into account an impact of SSM on soil roughness is recommended. Finally, the SMOSREX TB observations were assimilated by ISBA-DF. Considering CMEM as an observation operator provided a SSM and total soil water content analysis similar to the analysis obtained by assimilating direct SSM observations in ISBA-DF