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.

The work of the BEC team is not restricted to SMOS but also covers basic and applied research in other satellite remote sensing domains, like radar scatterometry and altimetry (ICM-CSIC) or GNSS reflectometry (UPC and ICE-CSIC). Now, six years after SMOS launch, the BEC is a consolidated research group in the international scene beyond the radiometric calibration and ocean salinity topics defined in 2007. A collaboration agreement has been recently signed between CSIC and UPC with the Institute of Space Studies of Catalonia (IEEC), a private, non-profit foundation in Barcelona and international leader in different aspects of space sciences. The objective of the agreement is to build synergies based on common strategies in the field of Earth observation, to allow an increase of scientific productivity, a more efficient participation in international satellite missions, and a joint work in designing and providing products for applications to stakeholders in the domains of climate change, oceanography, meteorology, and natural risks management. As a result, from January 2016 the IEEC is officially integrated in the BEC that becomes now the BARCELONA EXPERT CENTER ON REMOTE SENSING and widens its scope to cover all remote sensing topics of interest for the three entities.

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.

The research developed at BEC is two fold. On one side, it is focused on the improvement of the diagnostics of surface velocities from existing altimeters. In particular, it focuses on the exploitation of the SAR mode of the new generation of altimeters, such as the radar altimeter onboard Sentinel-3, to derive surface currents at spatial resolutions not achievable with previous instruments and techniques. On the other side, it is also focused on the exploitation of  Sea Surface Temperature (SST) observations in the infrared spectrum and its  synergy with Sea Surface Heigh (SSH) provided by altimeters. Recent results reveal that, this approach has the potential to significantly increase the spatial resolution of current estimations of surface currents.

Surface currents derived from altimetric maps

Surface currents derived from SST using the approach described in Isern-Fontanet et al. 2014

References

J. Isern-Fontanet and M. Shinde and C. Gonzalez-Haro (2014). On the transfer function between surface fields and the geostrophic stream function in the Mediterranean sea. J. Phys. Ocean,  44,  1406-1423

New experimental SMOS Sea Surface Salinity (SSS) maps at high latitudes, including Arctic Ocean open water regions, have been computed at BEC using a new methodological approach that substantially reduces land-sea and RFI contamination effects, as well as other intrumental biases.

SMOS Sea Surface Salinity map on 1st September 2011

The new product consists of 9-day, objectively analysed, EASE NL 25-km resolution gridded SSS maps. These maps are produced daily from 2011 to 2013.

The product is freely available at CP34-BEC web system, http://cp34-bec.cmima.csic.es/thredds/catalog/EARTOA025009DB, and browse its corresponding maps here.

The preliminary assessment of the product shows a RMS difference with respect to ARGO SSS of 0.34 psu (the quality report can be downloaded from here).

We hope that you will find this new product interesting and welcome your feedback.

Keep tuned!

Temporal evolution of SMOS Sea Surface Salinity at the Mackenzie river discharge region (in Beaufort Sea) during Summer 2012.

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 understand 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 the Sea Surface Salinity (SSS) 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 SST and 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.

Since 2007, DOFT-ICM engineers (Agustí Julià, Pere Fernández and Joaquin Salvador) in collaboration with the BEC team started to develop an ICM-SVPS buoy to measure temperature and salinity at 60 cm from the sea surface (fig. 1). Such drifter was specifically designed to fill the gap between the skin depth sampled by remote sensing (1 cm penetration depth) and the uppermost reliable measures from Argo profiles (between 5 and 10 m below the surface), necessary for cal/val activities of the SMOS and AQUARIUS missions. The body of the ICM-SVPS buoy consists on a spherical hull within the WOCE-SVP standard size range containing the batteries and the electronics and an external connector to communicate with additional sensors. The electronics has a modular structure, with a system of capacitors designed to minimize the energy expenditure. The electronic system is included in a single printed circuit board with an 8-bit micro controller being able to handle external instruments with RS232 and 24 bits DA converters.

For the SPURS experiment the buoys were attached to a holey-sock drogue centered at 15 m to move with the characteristic ocean surface velocity fields and were deployed in the region of maximum SSS for the North Atlantic Ocean, an area where salinity was expected to be very stable. Measurements, however, have displayed an unexpected high salinity variability due to the advection by strong currents in the southwestern part of the domain and the active eddy field near the centre (Reverdin, et al., 2015).

Salinity sensors from such buoys tend to be affected by the own sensor drift, temporary obstruction of objects and by the action of biofouling on conductivity cells producing biases in salinity values. Besides the difficulties to have reliable long term measurements of salinity with these devices, the SPURS experiment has also served to test the efficiency of the ICM-SVPS design in terms of durability and energy efficiency (figure 3). All the units have performed under operation above 900 days with an averaged lifetime of 980 days (2.6 years) emitting every 90 s and providing SSS measurements hourly.

Bibliography:

Reverdin G., Morisset S., Marié L., Bourras D., Sutherland G., Ward B., Salvador J., Font J., Cuypers Y., Centurioni L., Hormann V., Koldziejczyk N., Boutin J., D’Ovidio F., Nencioli F., Martin N., Diverres D., Alory G., Lumpkin R. 2015. Surface salinity in the north atlantic subtropical gyre during the STRASSE/SPURS summer 2012 cruise. Oceanography, 28(1):114-123.

Centurioni, L.R., V. Hormann, Y. Chao, G. Reverdin, J. Font, and D.-K. Lee. 2015. Sea surface salinity observations with Lagrangian drifters in the tropical North Atlantic during SPURS: Circulation, fluxes, and comparisons with remotely sensed salinity from Aquarius. Oceanography  28(1):96–105, http://dx.doi.org/10.5670/oceanog.2015.08

The Water Resources Research Group of the University of Salamanca has developed a new agricultural drought index, the so-called Soil Water Deficit Index (SWDI) [1], [2], based in soil moisture and soil parameters. Using the high resolution BEC L4 soil moisture product [3] as an input of the SWDI, agricultural drought maps of Zamora province (west of Spain) were derived (Fig. 1). With this product, agricultural drought conditions in the most important agricultural regions in Spain will be monitored.

The results of this research will be published soon, so stay tuned!

Fig.1. SWDI-SMOS map at 1 km spatial resolution of Zamora province showing wet (02/12/2010, Up) and dry (24/08/2011, Down) conditions.

[1] Martínez-Fernández, J., González-Zamora, A., Sánchez, N., & Gumuzzio, A. (2015). “A soil water based index as a suitable agricultural drought indicator.” Journal of Hydrology, 522, 265-273.

[2] Martínez-Fernández, J., González-Zamora, A., Sánchez, N., Gumuzzio, A., & Herrero-Jiménez, C.M. (2016). “Satellite soil moisture for agricultural drought monitoring: Assessment of the SMOS derived Soil Water Deficit Index.” Remote Sensing of Environment, 177, 277-286.

[3] Piles, M., Camps, A., Vall-llossera, M., Corbella, I., Panciera, R., Rüdiger, C., Kerr, Y.H., & Walker, J. (2011). “Downscaling SMOS-Derived Soil Moisture Using MODIS Visible/Infrared Data.” IEEE Transactions on Geoscience and Remote Sensing, 49, 3156-3166.

L4 SSS product. To product it, the new OA debiased SSS product is fused with OSTIA SST daily. The animation corresponds to a period from February to July 2015.

In a continuous effort to bring the higher quality products to our users, BEC is happy to announce that a new version of BEC SSS products (v2.00) has been put into operations.

In the new operational version, Land Sea Contamination has been mitigated by means of the empirical salinity debiasing method proposed in [Olmedo et al., 2016]. This leads to higher quality products that can be used for many different purposes. This new dataset is available at BEC products – Available variables – Sea Surface Salinity – Operational V2.0 section or by clicking here.

To address the different needs from our users, in version 2.00 we have developed several new products, which will be generated in a regular, operational basis:

• Daily gridded L2 map: This product is devoted to those users interested in working with L2 SMOS SSS data, but who are not familiar with the ESA standard format. All the L2 SSS satellite overpasses with the same orbit direction (i.e., ascending or descending, separately) and acquired on the same day are put together in a regular cylindrical 0.25º grid and distributed in NetCDF files.
• Monthly binned L3 map: This product aims to final users who are interested in global, calibrated  SMOS SSS maps mainly for climate applications. The previous versions of the BEC L3 maps were served on a 0.25º grid for an averaged period of 9 days. It was found that at those spatial and temporal resolutions, noise dominates over the geophysical structures. In this new release, the binned products are served at a 1º grid for an averaged period of one month.
• Objectively analyzed L3 map: This product is thought for ocean modelers and, in particular, those interested in mesoscale activity. Version 1.00 optimally interpolated (OI) BEC SSS maps have been replaced in version 2.00 by objectively analyzed (OA) SSS maps, using the same parameters as described in [Zeng et al., 2013]. OA L3 maps are generated as 9-day averages of L2 data on a 0.25º grid; they are served daily.
• Data fused L4 maps: This product is addressed to those users requiring high spatial and temporal resolution. Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) daily SST maps at a 0.05º (see [Donlon et al., 2012]) are used to increase the spatial and temporal resolution of the daily 9-day OA maps. The OSTIA system is part of the Group for High Resolution Sea Surface Temperature (GHRSST), and is currently distributed through the Copernicus web portal (http://marine.copernicus.eu/). Several fusion parameters have been tuned to improve the fused product, as described in [Olmedo et al., 2016].

In the following table, a summary of the quality of version 2.00, using Argo data as reference, is presented (more detailed information can be found in this Quality Report):

Please, do not hesitate to contact us in case you have any question or comment at smos-bec@icm.csic.es. Your feedback is most welcome!

[Donlon et al., 2012] Donlon, C. J., Martin, M., Stark, J., Roberts-Jones, J., Fiedler, E., & Wimmer, W. (2012). The operational sea surface temperature and sea ice analysis (ostia) system. Remote Sensing and Enviroment 116, 140–158.

[Olmedo et al., 2016] Olmedo, E., Martínez, J., Umbert, M., Hoareau, N., Portabella, M., Ballabrera-Poy, J., and Turiel, A. (2016). Improving time and space resolution of smos salinity maps using multifractal fusion. Remote Sensing of Environment 180, 246-263.

[Zweng et al., 2013] Zweng, M. M., Reagan, J. R., Antonov, J. I., Locarnini, R. A., Mishonov, A. V., Boyer, T. P., Garcia, H. E., Baranova, O. K., Johnson, D. R., Seidov, D., and Biddle, M. M. (2013). World Ocean Atlas 2013, Volume 2: Salinity. Levitus, Ed., A. Mishonov Technical Ed.; NOAA Atlas NESDIS 74, 39 pp.

The circulation in the Algerian Basin is characterized by the presence of fresh-core eddies that  propagate along the coast or at distances between 100-200 km from the coast. Significant improvement in the  processing of the Soil Moisture and Ocean Salinity (SMOS) data have allowed to produce, for the first time, satellite Sea Surface Salinity (SSS) maps in the Mediterranean Sea that capture the signature of Algerian eddies. SMOS data can be used to track them for long periods of time, especially during winter. SMOS SSS maps are well correlated with in situ measurements although the former has a smaller dynamical range. Despite this limitation, SMOS SSS maps capture the key dynamics of Algerian eddies allowing to retrieve velocities from SSS with the correct sign of vorticity. These results have been recently published in Geophysical Research Letters (Isern-Fontanet et al. 2016).

Three years (2011-2013) of SSS were derived from Brightness Temperatures (BT) measured by SMOS and provided by the European Space Agency (ESA). SMOS data were processed according to Olmedo et al. (2016) and used to generate a SSS map by means of a classical scheme of objective analysis applied over time periods of 9-days. Besides, numerical simulations of the circulation in the Mediterranean Sea have confirmed the strong tendency of the Sea Surface Temperature (SST) and SSS gradients to align (Isern-Fontanet et al. 2016). This property has been exploited to improve SSS maps using the methodology proposed by (Olmedo et al. 2016a), that combines information from SSS and SST. For this study, satellite-derived SSS were merged with Reynolds SST downloaded from NOAA. The resulting fields are available here. In addition, Absolute Dynamic Topography (ADT) maps provided by AVISO have been used to assessthe capabilities of SSS maps.

The film below shows the temporal evolution temporal evolution of SMOS SSS maps with the SSH contours over-plotted. The center of two Algerian eddies is identified with black dots. Although some problems are still evident in these images (temporal variation of the SSS amplitude, disappearance of some eddies) there is a good agreement between the patterns seen in SSH and SSS anomalies for the strongest signals. This coherence, however, has a clear seasonal signal with the best conditions to observe Algerian eddies being in winter.

The capability to detect the signature of Algerian eddies opens the door to overcome the sampling limitations of current altimetric observations (Pascual et al. 2006) through the uses of SMOS observations. We have tested this idea by repeating the study of  Isern-Fontanet et al. (2006) with the new SSS fields. The image below shows SSH anomaly with the geostrophic velocities overplotted (left), the SST anomaly with the velocities derived from SST (middle), and the SSS anomaly with the velocities derived from SSS (right) corresponding to 12 May 2011. As it is evident from the figure only the SSS is able to reproduce the correct polarity of Algerian vortices as already discussed by Isern-Fontanet et al. (2014).

Yes, for the first time it has been possible to detect Algerian eddies in satellite-derived SSS
maps derived from SMOS measurements. It has been also shown that the capability to detect such vortices is stronger during winter and the strong potential for SMOS measurements for computing surface currents.

References

Isern-Fontanet J., M. Shinde and C. González-Haro (2014), “On the transfer function
between surface fields and the geostrophic stream function in the Mediterranean sea”. J.
Phys. Ocean 44, 1406–1423, doi:10.1175/JPO-D-13-0186.1.

Isern-Fontanet J., E. Olmedo, A. Turiel, J. Ballabrera-Poy, and E. García-Ladona (2016),
“Retrieval of eddy dynamics from SMOS Sea Surface Salinity measurements in the Algerian Basin
(Mediterranean Sea)”. Geophys. Res. Lett. 43,  doi:10.1002/2016GL069595.

Pascual A., Y. Faugere, G. Larnicol, and P. Le Traon (2006), “Improved description of the ocean
mesoscale variability by combining four satellite altimeters”. Geophys. Res. Lett. 33, L02 611,
doi:10.1029/2005GL024633.

Olmedo E., J. Martínez, A. Turiel, J. Ballabrera-Poy, and M. Portabella (2016a) “Enhanced retrieval of the geophysical signature of SMOS SSS maps”. Remote Sensing of Environment, (Submitted).

Olmedo E., J. Martínez, M. Umbert, N. Hoareau, M. Portabella, J. Ballabrera-Poy, and A. Turiel (2016b). “Improving time and space resolution of smos salinity maps using multifractal  fusion”. Remote Sensing of Enviroment, doi:10.1016/j.rse.2016.02.038.

On November 2nd, 2016, SMOS mission accomplished a new feat: the mission has now been operating for seven years!

Designed for a nominal lifetime of three years plus an extension of two years, SMOS has overcome the expectations and it is now headed for a third extension period. And the instrument is still behaving well, giving rise to new products and applications on land, ocean, and cryosphere, and even for atmospheric applications.

Congratulations to SMOS and to ESA. Long life to SMOS!

The BEC team.

Fig. 1: Outliers distribution (red dots) is homogeneous in both versions. The nearest points to the coast are also excluded from statistics.

Since last September, Remote Sensing Systems (REMSS) is producing version 2.0 of the Level 2 and Level 3 Sea Surface Salinity products from SMAP. One year ago, we published in this blog a brief study on the validation of  version 1.0 of the 8-day L3 SSS maps provided by REMSS (see Preliminary validation of 8-day SMAP L3 Salinity product V1.0 for more information). Now, in order to assess the improvements of this new version, we present a small comparison between these two versions of the 8-day SSS L3 maps. Part of this study was included in the V2.0 Release Notes document. The validation has been made using as reference field the 7-day global ocean 0.25-degree SSS FOAM product generated by Met Office and distributed by Copernicus.

Fig. 2: SMAP SSS v1.0 (top) and v2.0 (bottom) minus FOAM reference field. Latitudinal mean

Spatial outliers have been eliminated by analyzing the statistics in the neighborhood of each grid point. For a given grid point, its neighborhood consists of itself and its closest 8 neighbors.  The associated 9 SSS values are used to compute the first and the third quartiles (Q1 and Q3) of the neighborhood. If the value of SSS for the central point lies outside the range [Q1-1.5 x IQR : Q3+1.5 x IQR] (IQR = Q3-Q1), the point is assumed to be an outlier and discarded. Points with less than 6 neighbors are also discarded.

Both versions of the 8-day L3 maps are compared with the FOAM reference field, and the latitudinal mean of the difference is computed for each map (figure 2). Version 2 shows a clear improvement at high latitudes. The discrepancies with respect to the reference field found around 10^oN are probably due to the high variability induced by the North Equatorial Current.

Fig. 3: SMAP SSS v1.0 (top) and v2.0 (bottom) minus FOAM reference field mean as a function of the distance to the nearest coast

Fig 4: Mean, median and mode for 8-day SMAP SSS L3 maps minus the FOAM reference field (version 1.0 at the top and version 2.0 in the middle.) Bottom figure shows the standard deviation of SMAP products minus the reference field for both versions (red, version 1.0 and blue version 2.0).

The improvement of version 2.0 with respect to v1.0 is also clear when SSS is compared as a function of the distance to the coast (figure 3).

Global statistics (between 60^oS and 60^oN) have also been computed. In figure 4, we show the evolution of the mean, median, mode and standard deviation of the difference to the reference for each 8-day global map. The mode has been computed, using the Freedman Diaconis estimator to compute the width of the bins (ℎ=/∛N, where N is the number of values in the dataset) and convolving the resulting distribution with a Gaussian kernel. The comparison of both versions shows a clear improvement of the distributions of SMAP minus reference differences for version 2.0: the mode remains close to 0 in v2.0. Moreover, the mean, median and mode show smaller temporal variations. Despite having symmetric distributions until mid july 2015, the skewness becomes negative from that date on. The global standard deviation (bottom of figure 4) also shows smaller values for the v2.0 SSS product.

Acknowledgement

SMAP data used in this study are produced by Remote Sensing Systems and sponsored by the NASA Ocean Salinity Science Team. They are available at www.remss.com

References

Meissner, T. and Wentz, F.J. (2016). Remote sensing systems SMAP Ocean Surface Salinities [Level 2C. Level 3 Running 8-day, Level 3 Monthly], Version 2.0 validated release. Remote Sensing Systems, Santa Rosa, CA. Available at http://www-remss.com/missions/smap, doi:0.5067/SMP20-3SPCS.

We are pleased to inform you that our paper “Debiased non-Bayesian retrieval: A novel approach to SMOS Sea Surface Salinity” has recently appeared in Remote Sensing of Environment.

In the paper, we present a new method to process SMOS data in order to obtain more precise, less biased values of Sea Surface Salinity (SSS). With the new methodology, we do not only improve the overall quality of SSS data, but we also obtain valid retrievals in areas previously deemed as inaccessible, such as the Mediterranean.

In the standard SSS retrieval algorithm used so far at SMOS DPGS, all the values of TB referred to a specific geographic location and satellite overpass are processed together for the retrieval of the associated SSS, using a single, Bayesian cost function. The new method, in contrast, is based in the individualized processing of each value of brightness temperature TB obtained for any specific geographic location, because depending on the location in the antenna plane TB values suffer different biases. The biases are characterized, then corrected, using SMOS-based climatologies.

The new method leads to a more than remarkable increase in quality over the global ocean, and an improvement of the coverage of SSS data, especially in coastal areas.

This method is currently being applied for the generation of our advanced products, an update of those products is forthcoming.

Enjoy!

The BEC Team

Objectively Analysed SSS for the period May 27th to June 4th, 2014

In a continuous effort to improve the quality of our data and provide a better service to our users, we have made a new brand of advanced SSS products available. In contrast with previous datasets, the new products have global coverage and are generated for a 6-year period.

The new products are based in the debiased non-Bayesian method, as the previous ones. Some minors issues regarding the definition of the SMOS-based climatologies have been improved for the production of this new dataset.

The dataset includes the same types of products and with the same spatial and time resolution of the Mediterranean products we introduced one year ago, but with increased coverage both in space (now global) and time (now six years, from 2011 to 2016).

For that reason, the Mediterranean products are now considered deprecated and  will be removed from our servers in some months.

Arctic SSS products, as they require specific spatial grid and other adaptations, will be preserved.

The use of debiased non-Bayesian method allows to mitigate the effect of land-sea contamination and a significant part of the negative impact by radiofrequency interferences (RFI). There are still some areas so impacted by strong RFI that cannot be retrieved, and for which specific processing methods are being investigated. Nevertheless, in the vast majority of the ocean and coastal areas the new products are of a quality good enough to enable users to study and analyze many geophysical processes.

As usual, we expect to have your feedback on our products; do not hesitate in contacting us at smos-bec@icm.csic.es.

Enjoy!

The BEC Team

Tweet

Past June 19th we celebrated the 10th anniversary of the foundation of the Barcelona Expert Center.

We were honored of counting with the presence of the  Minister of Agriculture, Livestock, Fishing and Food of Generalitat de Catalunya, Ms. Meritxell Serret, and of the deputy Vicepresident for Scientific-Technical Areas of CSIC, Dr. Victoria Moreno, who highlighted the institutional importance of BEC for CSIC and for Catalonia.

Prof. Jordi Font,  retired CSIC researcher, SMOS co-PI and founder of BEC, shared with us his personal overview of the SMOS mission and what BEC had represented during the years he had headed it. It was a very good introduction to what BEC was and to what BEC is becoming.

Dr. Susanne Mecklenburg, SMOS Mission Manager, ESA, explained what SMOS has represented, a real challenge but successful mission in Earth Observation, and highlighted the brilliant possibilities for any continuation mission on L-band radiometry.

To finish the first block of talks, Ms. Andrea Pérez-Carro, CDTI and Spanish representative in Copernicus, presented and discussed the future priorities for Copernicus in Earth Observation, putting into context what a possible future mission on L-band could be.

After this introductory block, many other presentations followed during the rest of the day: Yann Kerr (from CESBIO and SMOS PI), Pedro Mier (Tryo Mier), Ignacio Tourné (Deimos), Andrés Borges (Airbus), Manuel Martín Neira (ESA), Antonio Turiel (CSIC and BEC Head),  Roberto Sabia (Telespazio Vega), Ignasi Corbella (UPC & BEC), Francesc Torres (UPC & BEC), Verónica González-Gambau (CSIC & BEC), Manuel Arias (Argans), Estrella Olmedo (CSIC & BEC), Jacqueline Boutin (LOCEAN), Justino Martínez (CSIC & BEC), Nicolas Reul (IFREMER and presently ocean salinity scientific leader), Carolina Gabarró (CSIC  and BEC director), Marcos Portabella (CSIC & BEC) and Mercè Vall-llossera (UPC & BEC Vice-head).

We thank all of you for having shared with us a very special day, and we hope to host all of you again in ten years from now!

The BEC team

Demonstrations against the violence all over Catalonia, October 3rd, 2017

On October 1st, 2017, many Catalans waited in front of the voting stations to participate in a referendum to decide the future of Catalonia. The Spanish Constitutional Court had suspended the referendum, but nevertheless the regional government decided to go ahead with the poll. The response by the Spanish Government was to concentrate in Catalonia a massive amount of anti-riot police squads during the previous days, with the order of prevent the voting to take place. Many were convinced that they would never dare to attack the peaceful hundreds of thousands of citizens, that they will just take the ballots and ballot boxes away, and that the voting day will be just a political demonstration, a tour de force between Catalan independentists and the Spanish Government. They were deadly wrong.

The extreme use of the force by the Spanish policemen terrified the people that was just standing up in front of them, raised arms and singing. The media have reproduced horrifying witnesses of the brutal, unjustified and disproportionate use of the strength against the population that just wanted to express a political opinion. Many of us at BEC know well what happened, as we were at the poll stations and saw the indiscriminate use of violence or waited in the lines in the anguish of knowing that they could appear at any time and attack us in sight with no reason.

BEC does not endorse any political position, as in our team all the opinions can be found; but this disparity of opinions does not prevent a friendly respect of each other, as it happens in mature democratic societies. This has nothing to do with what we saw past Sunday.

Visca Catalunya!

The BEC team

Monitoring sea ice concentration is required for operational and climate studies in the Arctic Sea. Technologies used so far for estimating sea ice concentration have some limitations, for instance the impact of the atmosphere, the physical temperature of ice, and the presence of snow and melting. In the last years, L-band radiometry has been successfully used to study some properties of sea ice, remarkably sea ice thickness. However, the potential of satellite L-band observations for obtaining sea ice concentration had not yet been explored.

In this paper, we present preliminary evidence showing that data from the Soil Moisture Ocean Salinity (SMOS) mission can be used to estimate sea ice concentration. Our method, based on a maximum-likelihood estimator (MLE), exploits the marked difference in the radiative properties of sea ice and seawater. In addition, the brightness temperatures of 100 % sea ice and 100 % seawater, as well as their combined values (polarization and angular difference), have been shown to be very stable during winter and spring, so they are robust to variations in physical temperature and other geophysical parameters. Therefore, we can use just two sets of tie points, one for summer and another for winter, for calculating sea ice concentration, leading to a more robust estimate.

After analysing the full year 2014 in the entire Arctic, we have found that the sea ice concentration obtained with our method is well determined as compared to the Ocean and Sea Ice Satellite Application Facility (OSI SAF) dataset. However, when thin sea ice is present (ice thickness ≲ 0.6 m), the method underestimates the actual sea ice concentration.

Our results open the way for a systematic exploitation of SMOS data for monitoring sea ice concentration, at least for specific seasons. Additionally, SMOS data can be synergistically combined with data from other sensors to monitor pan-Arctic sea ice conditions.

https://www.the-cryosphere.net/11/1987/2017/

Ocean currents play a key role in Earth’s climate – they impact almost any process taking place in the ocean and are of major importance for navigation and human activities at sea. Nevertheless, their observation and forecasting are still difficult. First, no observing system is able to provide direct measurements of global ocean currents on synoptic scales. Consequently, it has been necessary to use sea surface height and sea surface temperature measurements and refer to dynamical frameworks to derive the velocity field. Second, the assimilation of the velocity field into numerical models of ocean circulation is difficult mainly due to lack of data. Recent experiments that assimilate coastal-based radar data have shown that ocean currents will contribute to increasing the forecast skill of surface currents, but require application in multidata assimilation approaches to better identify the thermohaline structure of the ocean. In this paper we review the current knowledge in these fields and provide a global and systematic view of the technologies to retrieve ocean ve- locities in the upper ocean and the available approaches to assimilate this information into ocean models.

To download the published paper click here.

Sea surface temperature from AVHRR. Upper left: absolute dynamic topography from AVISO (black lines) and the associated geostrophic velocities (arrows). Top right: velocities derived from a sequence of thermal images using the MCC method (arrows). Bottom: velocities derived from the thermal image using a Butterworth filter (arrows)

A new methodology using a combination of debiased non-Bayesian retrieval, DINEOF (Data Interpolating Empirical Orthogonal Functions) and multifractal fusion has been used to obtain 6 years of SMOS Sea Surface Salinity (SSS) fields over the North Atlantic Ocean and the Mediterranean Sea. This product has been developed by the Barcelona Expert Center and the GHER group at University of Liège (Belgium), under the ESA STSE project “SMOS sea surface salinity data in the Mediterranean Sea (SMOS+ Med)”. SMOS+ Med was leaded by Dr. Aida Alvera-Azcarate, from GHER.

The complete description of the methodology as well as the analysis of the quality assessment of the product can be found in Olmedo, E. et al., Improving SMOS Sea Surface Salinity in the Western Mediterranean Sea through Multivariate and Multifractal Analysis, Remote Sensing, 2018, 10(3).

The debiased non-Bayesian retrieval mitigates the systematic errors produced by the contamination of the land over the sea. In addition, this retrieval improves the coverage by means of multiyear statistical filtering criteria. This methodology allows having valid values of SMOS SSS  in the Mediterranean Sea, something deemed impossible when the mission was designed. However, the resulting SSS suffers from a seasonal (and other time-dependent) bias. Those time-dependent biases have been characterized by means of specific Empirical Orthogonal Functions (EOFs) and removed from the SSS signal. Finally, high resolution Sea Surface Temperature (OSTIA SST) maps have been used for improving the spatial and temporal resolution of the SMOS SSS maps. The presented methodology practically reduces the error of the SMOS SSS in the Mediterranean Sea by half. As a result, the SSS dynamics described by the new SMOS maps in the Algerian Basin and the Balearic Front agrees with the one described by in situ SSS, and the mesoscale structures described by SMOS in the Alboran Sea and in the Gulf of Lion are in good agreement with the ones described by the high resolution remotely-sensed SST images (AVHRR)

The products can be downloaded from our THREDDS server. It is also possible browse objective analysed product and fused product using our WMS server.

Remember that you can access to our data following a simple registering process.

Enjoy!

The BEC team.

In a continuous effort to improve the quality of our data and provide a better service to our users, we present the new SMOS Sea Ice Concentration (SIC) product for the Arctic Ocean .

The new product is based on the algorithm presented in the paper Gabarro et al., 2017 [1]. The algorithm uses the differences between vertically-polarized brightness temperature (TB) measurements of two different incidence angles (i.e., angular differences or AD) and a Maximum-likelihood estimation to retrieve SIC. This AD index has lower sensitivity to cganfes in ice temperature, ice salinity and thin ice thickess (see [1] for more details) than the TB measurements, and is therefore more suitable for SIC retrievals.

The daily Arctic Sea Ice Concentration (SIC) product is provided in the NL EASE grid (25km x 25km) and consists of a 3-day averaging of the ascending and descending SMOS Level 1B data provided by ESA (v6.20).

Due to the higher penetration of the L-band signal on the sea ice, SMOS underestimates SIC in the presence of thin ice (less than approx. 70 cm), which usually happens over marginal ice zones and freeze-up periods (October-March). Therefore, the SMOS data should be used taking it into account. The SMOS-derived SIC estimations can complement those from higher-frequency radiometers, yielding to enhanced SIC products.

A more detailed description of the methodology and the product can be found in the Product Description document available from the BEC webpage.

Please, do not hesitate to contact us in case you have any question or comment at smos-bec@icm.csic.es. Your feedback is most welcome!

Enjoy the products!

BEC team

[1] New methodology to estimate Arctic sea ice concentration from SMOS combining brightness temperature differences in a maximum-likelihood estimator,C. Gabarro, , A. Turiel, P. Elosegui, J.A. Pla-Resina, M. Portabella. The Cryosphere,11:4,1987–2002,2017. DOI: 10.5194/tc-11-1987-2017- https://www.the-cryosphere.net/11/1987/2017/

We are pleased to announce the new near real-time global SMOS L3 soil moisture products v003. These products have different averaging periods (and frequency rates): 1-day (daily) maps in both ISEA 4H9 and EASE-2 25 km, and 3-day (daily), 9-day (every 3 days), 1-month (monthly) and 1-year (yearly) maps in EASE-2 25 km. All of them have been generated using the latest version of SMOS L2 soil moisture processor (v650, which supersedes the previous L2 v620). The main improvements of v650 are related to algorithm updates, parameters configuration and auxiliary files changes.

A general vision of all near real-time L3 soil moisture products served is available at land datasets page. Additionally, a detailed description of the methodology followed to generate these products can be found in the BEC Land Products Description. These near real-time products can be downloaded (after free registration) from our thredds server. Also an on-line map browser is available.

Please, do not hesitate to contact us in case you have any question or comment at smos-bec@icm.csic.es. Your feedback is most welcome!

Enjoy the products!

BEC team

Three years ago, the BEC team introduced a new method for the retrieval of SSS from SMOS data: the debiased non-Bayesian approach. The method was first used to derive the first maps of SMOS SSS in the Mediterranean.

After three years, we have extensively validated the method, first in the Mediterranean, then in the Arctic and finally globally.The debiased non-Bayesian approach is now a consolidated technique, and reportedly the one providing the best estimates of SSS using SMOS data in any area of the global ocean.

In the next months, we plan to introduce new improvements. Very soon, we are going to serve an extended series of improved Arctic SSS maps. And in some months from now, we will deliver the first SSS maps ever in a very challenging area: the Baltic Sea. And this is only the beginning: we plan to ensure an almost operational generation of all debiased non-Bayesian SSS maps (that is, the maps will be generated with a short delay, a few weeks at most).

With the debiased non-Bayesian SSS becoming operational and being by far our best SSS product, it was no longer meaningful to maintain the old “operational” brand: a line of Level 3&4 SSS products directly derived from ESA official L2 products. For that reason, as of November 13th, 2018, the Level 3 & 4 SSS maps derived from ESA L2 data are no longer available at this webpage. We will keep a copy of those data for two years. Any interested user can request them, but they will not be longer processed or extended.

Therefore, from now on there is only one brand of SSS products, that corresponds to the former “Advanced” family (debiased non-Bayesian). This brand is presented with different processing levels (Level 3 and Level 4), time and space resolutions, and is offered at global scale and for some selected regions (Arctic, Mediterranean and soon Baltic).

This is not the only upcoming change. In order to facilitate access to users, in some weeks from now we are going to substitute our present Thredds server by a new SFTP server. For technical reasons we cannot maintain both, so be aware that a given moment your Thredds scripts will no longer be valid, and you should move to the new sftp scripts. We will warn the users some days before the change, and the help desk will provide guidance to fix any trouble arising.

We foresee new changes in the next months, regarding formats, meta-data, grids and other conventions, and also including new variables. We also foresee to produce and distribute new products for new applications. We will soon survey our users to know their opinion before implementing that batch of changes, and we will inform them about the final outcome and decisions.

There are new, exciting times coming at BEC. Keep tuned!

The BEC team.

Seven years (2011–2017) of 25 km nine-day Soil Moisture and Ocean Salinity (SMOS) Sea Surface Salinity (SSS) objectively analyzed maps in the Arctic and sub-Arctic oceans (50∘ N–90∘ N) are now available in our website.

Discharge of Mackenzie river captured by BEC Arctic SSS product

The new SMOS SSS maps are an improved version of the preliminary three-year dataset generated and freely distributed by the Barcelona Expert Center. In this new version, a time-dependent bias correction has been applied to mitigate the seasonal bias that affected the previous SSS maps. An extensive database of in situ data (Argo floats and thermosalinograph measurements) has been used for assessing the accuracy of this product. The standard deviation of the difference between the new SMOS SSS maps and Argo SSS ranges from 0.25 and 0.35. The major features of the inter-annual SSS variations observed by the thermosalinographs are also captured by the SMOS SSS maps. However, the validation in some regions of the Arctic Ocean has not been feasible because of the lack of in situ data. In those regions, qualitative comparisons with SSS provided by models and the remotely sensed SSS provided by Aquarius and SMAP have been performed. Despite the differences between SMOS and SMAP, both datasets show consistent SSS variations with respect to the model and the river discharge in situ data, but present a larger dynamic range than that of the model. This result suggests that, in those regions, the use of the remotely sensed SSS may help to improve the models.
A complete description of the methodology used in the generation of this product and a quality assessment can be found in Olmedo et al, 2018, RS (available in https://www.mdpi.com/2072-4292/10/11/1772 ).