New methodology to estimate Arctic sea ice concentration from SMOS combining brightness temperature differences in a maximum-likelihood estimator

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.

figura_SIC_2

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/

The Cryosphere, 11, 1987-2002, 2017
https://doi.org/10.5194/tc-11-1987-2017

 

BEC joins public condemnation of the use of violence against Catalan people

IMG_20171005_095405


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

Celebration of BEC 10th Anniversary

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.

20170619_10años BEC (58)

…read more

Advanced SSS products now available with global coverage!

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

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.

…read more

Debiased non-Bayesian retrieval: A novel approach to SMOS Sea Surface Salinity

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.

…read more

Preliminary SWDI maps using the BEC L4 soil moisture product

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!

Zamora1a

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.

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.

A big tour sampling the North Atlantic ocean

 

google_a

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.

…read more

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.
…read more

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!
L3BIN_MONTHLY_100 …read more