A big tour sampling the North Atlantic ocean

 

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In march 2013 an international experiment, the Salinity Processes in the Upper ocean Regional Study (SPURS), was carried out with the goal of performing a wide range of mesoscale and submesoscale measurements to contribute to understanding the mechanisms of formation and permanence of the largest ocean salinity maximum in the centre of the North Atlantic subtropical gyre. Several standard and prototype instruments were used in measuring sea surface salinity and other ocean variables. Among many activities developed during the SPURS-MIDAS cruise, the ICM contribution to SPURS, a set of new Lagrangian drifters to measure the Sea Surface Temperature (SST) and Salinity (SSS) were deployed. These were part of a total set of 114 similar drifters deployed during the whole experiment (Centurioni et al, 2015). Now almost three years later three of these units are still providing data after performing a big tour around the North Atlantic.

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New Research: Ocean Currents at BEC

Ocean currents are a key element for the understanding of many oceanic and climatic phenomena and their knowledge is crucial for navigation and operational applications. Following the official broadening of its scope, BEC has extended its research activity towards the diagnosis of ocean surface currents from satellite observations. This new research line, led by Dr. Jordi Isern-Fontanet, is being funded through the ComFuturo program (http://comfuturo.es/proyectos/) granted by the Fundación General del CSIC (http://www.fgcsic.es/) and through the GlobCurrent project (http://www.globcurrent.org/) funded by ESA.
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BEC officially broadens its scope

The SMOS-BEC (SMOS-BARCELONA EXPERT CENTER ON RADIOMETRIC CALIBRATION AND OCEAN SALINITY) was created in July 2007 by agreement between CSIC (Spanish Research Council) and UPC (Technical University of Catalonia) to enhance coordination and visibility of both institutions in their joint work in processing data from the SMOS mission. It was installed in the Centre Mediterrani d’Investigacions Marines i Ambientals (CMIMA) building, belonging to CSIC and that also hosts the Institut de Ciències del Mar (ICM) and the Unitat de Tecnologia Marina (UTM), in the Barcelona sea front. The UPC participation is made through the Passive Remote Sensing Group / Remote Sensing Lab from the Department of Signal Theory and Communications. The main CSIC actor in SMOS is the Physical and Technological Oceanography Department from ICM, together with the Earth Observation Group from the Institut de Ciències de l’Espai (ICE).

BEC scientists play a key role in the mission: Jordi Font (ICM) is the SMOS Co-Lead Investigator for ocean salinity, Ignasi Corbella (UPC) and Antonio Turiel (ICM) are members of the SMOS Quality Working Group, the BEC-UPC team is an Expert Support Laboratory to ESA for the SMOS level 1 processor definition and development, and the BEC-ICM team is an ESL for the level 2 ocean salinity processor. The BEC proposed, designed and validated the level 3 and level 4 SMOS products generated in CP34, Centro de Producción de datos SMOS de niveles 3 y 4, an additional Spanish contribution to the mission to build and operationally distribute SMOS added value products beyond the level 2 official ESA data. CP34 was operated at ESAC, the ESA establishment near Madrid that hosts the SMOS Data Processing Ground Segment, until July 2013. Then it was moved to BEC facilities, where an improved web site allows now an easy access to operational and experimental SMOS level 3 and 4 products, with user friendly format plus additional information to the international users community. …read more

Preliminary validation of 8-day SMAP L3 Salinity product V1.0

Atlantic discharges. April 25-May 2, 2015

Amazon, Niger and Congo discharges over the Atlantic Ocean as measured by SMAP

Scientists at Remote Sensing Systems (RSS, http://www.remss.com), using the experience acquired with the Aquarius mission are developing the necessary algorithms to retrieve sea surface salinity from brightness temperature provided by the SMAP radiometer team.

Recently, RSS has released version 1.0 (BETA) SMAP Level 3 Ocean Surface Salinities. The data can be accessed through the RSS web site or FTP server and it is described in [Meissner et al., 2015]. Their Level 3 salinity product has worldwide coverage and correspond to  8-day and monthly averages. The 8-day average field, centered on each day, starts on April 4, 2015 and ends at November 15, 2015.

A preliminary comparison of the 8-day L3 product with ARGO profiles and the World Ocean Atlas (WOA13) climatology has been performed by BEC team over the zones indicated on the map below.

Zones under study

Zones under study (click to enlarge image)

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Effective SMOS PSF and Antenna Correlations

Given the interferometric characteristics of SMOS, SMOS snapshots are full-polarization brightness temperatures rendered on a hexagonal grid (the so-called synthetic antenna). In fact, what the instrument actually measures are the cross-correlations of all pairs of receivers, from which a visibility function can be derived. The vector of visibilities is linearly related to brightness temperatures TB by means of a reconstruction matrix G. Due to the imperfect knowledge of the matrix G, the difficulties to invert such a big matrix together with some aliasing effects, spurious spatial correlations on brightness temperature snapshots are induced. BEC team is investigating the scope of such correlations. The shape of the found correlations reveals a clear geometrical pattern.

X polarization correlation pattern

a) X polarization correlation pattern. Correlation of the central point with the rest of the synthesized scene

X polarization correlation pattern

b) Real part of XY polarization correlation pattern. Correlation of the central point with the rest of the synthesized scene

X polarization correlation pattern

c) X polarization correlation pattern. Correlation of a point located in the edge of AF-FOV with the rest of the synthesized scene

X polarization correlation pattern

d) X polarization correlation pattern. Correlation of a point beyond the horizon with the rest of the synthesized scene

Figure 1.- Correlation patterns for different polarizations and antenna points. Patterns corresponding to polarization Y and to the imaginary part of cross polarization are similar to those corresponding to X polarization (figures 1.a, 1.c and 1.d) and real part of cross polarization respectively (figure 1.b).

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Preliminary SMOS SSS in the Mediterranean

Experimental SMOS SSS maps of the Mediterranean Sea are being computed at BEC using a new methodological approach to cope with land and RFI contamination. Three different products are being analysed: monthly binned maps at a 1×1 deg grid; optimal interpolated maps at 0.25×0.25 deg; and daily products at 0.25×0.25 deg through fusion with Reynolds SST.  The preliminary assessment of the monthly product shows an RMS with respect to ARGO of 0.35 psu. These maps will be available soon in our CP34-BEC data distribution system, so keep watching!
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Using Argo to validate remote sensing missions

With its more than 3500 automatic profilers, the Argo array is one of the most important component of the Global in-situ Ocean Observing System. The array provides measurements of temperature and salinity profiles down to 2000 m. These data are rapidly expanding the historical database of the ocean sub-surface (specially in the case of ocean salinity) and are providing novel information about the ocean’s vertical structure and its variability. Moreover, these data allow real-time monitoring, model-constraining and contribute to calibration and verification efforts.

Number of available profiles from January 2005 to December 2014: Shown are the total number of profiles, the delayed mode profiles as for Apri 27, 2015 and the number of delayed mode profiles with salinity.

Figure 1: Number of Argo profiles from January 2005 to December 2014: Shown are the total number of profiles, the delayed mode profiles as for April 27, and the number of delayed mode profiles with salinity.

The Euro-Argo (www.euro-argo.eu) research infrastructure, designed to coordinate the European contribution to Argo, is part of the European Strategy Forum on Research Infrastructures (ESFRI). Euro-Argo is expected to provide additional 50 floats per year and support about the 25% of
the Argo array.

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SMOS Sea Ice Concentration maps

Since more than a year ago, the Barcelona Expert Center (BEC) team researches on the capabilities of SMOS for the characterizations of the Cryosphere. 

First maps of the Arctic Sea Ice concentration from SMOS data have been produced for the year 2014, with the algorithm explained bellow.

SMOS_Mar_2014

 

Two indices have been chosen to compute ice concentration: Angular Difference (AD=TBV(θ_2)-TBV(θ_1)) and Polarization Difference (PD=TBV-TBH). The sensitivity of those indices to ice salinity and temperature is much less (about 60%) than that of raw TB’s, but they are still quite sensitive to the physical state (sea or ice). This property is very convenient for the empirical characterization of the physical state, because the distribution of the geophysical parameters is not very well known (specially for the ice salinity).

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