ESSDD

Earth System Science Data Discussions

ESSDD

Earth Syst. Sci. Data Discuss.

1866-3591

Göttingen, Germany

10.5194/essd-2021-364

New SMOS SSS maps in the framework of the Earth Observation data For Science and Innovation in the Black Sea

Olmedo

Estrella

¹ González-Gambau

Verónica

¹ Turiel

Antonio

https://orcid.org/0000-0001-6103-224X

¹ González-Haro

Cristina

https://orcid.org/0000-0003-4602-852X

¹ García-Espriu

Aina

¹ Gregoire

Marilaure

² Álvera-Azcárate

Aida

https://orcid.org/0000-0002-0484-4791

² Buga

Luminita

³ Rio

Marie-Hélène

⁴

Barcelona Expert Center (BEC) and Institute of Marine Sciences (ICM), CSIC, P. Marítim de la Barceloneta, 37-49, 08003 Barcelona, Spain

University of Liege

National Institute for Marine Research and Development Grigore Antipa

European Space Agency

18 11 2021

2021 1 40

2021

This work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/

This article is available from https://essd.copernicus.org/preprints/essd-2021-364/

The full text article is available as a PDF file from https://essd.copernicus.org/preprints/essd-2021-364/essd-2021-364.pdf

<p>In the framework of the European Space Agency (ESA) regional initiative called Earth Observation data For Science and Innovation in the Black Sea (EO4SIBS), a new dedicated Soil Moisture and Ocean Salinity (SMOS) Sea Surface Salinity (SSS) product is generated for the Black Sea for the years 2011–2020. Three SMOS SSS fields are retrieved and distributed: a level 2 product consisting of binned SSS in daily maps at 0.25° × 0.25° spatial resolution grid by considering ascending ((Olmedo et al., 2021b), <a href="https://doi.org/10.20350/digitalCSIC/13993" target="_blank" rel="noopener">https://doi.org/10.20350/digitalCSIC/13993</a>) and descending ((Olmedo et al., 2021c), <a href="https://doi.org/10.20350/digitalCSIC/13995" target="_blank" rel="noopener">https://doi.org/10.20350/digitalCSIC/13995</a>) satellite overpass directions separately; a level 3 product ((Olmedo et al., 2021d), <a href="https://doi.org/10.20350/digitalCSIC/13996" target="_blank" rel="noopener">https://doi.org/10.20350/digitalCSIC/13996</a>) consisting of binned SSS in 9-day maps at 0.25° × 0.25° grid by combining as cending and descending satellite overpass directions; and a level 4 product ((Olmedo et al., 2021e), <a href="https://doi.org/10.20350/digitalCSIC/13997" target="_blank" rel="noopener">https://doi.org/10.20350/digitalCSIC/13997</a>) consisting of daily maps at 0.05 × 0.0505° that are computed by merging the level 3 SSS product with Sea Surface Temperature (SST) maps. The generation of SMOS SSS fields in the Black Sea requires the use of enhanced data processing algorithms for improving the Brightness Temperatures in the region since this basin is typically strongly affected by Radio Frequency Interference (RFI) sources which hinders the retrieval of salinity. Here, we describe the algorithms introduced to improve the quality of the salinity retrieval in this basin. The validation of the EO4SIBS SMOS SSS products is performed by: i) comparing the EO4SIBS SMOS SSS products with near-to-surface salinity measurements provided by in situ measurements; ii) assessing the geophysical consistency of the products by comparing them with a model and other satellite salinity measurements; iii) computing maps of SSS errors by using Correlated Triple Collocation analysis. The accuracy of the EO4SIBS SMOS SSS products depend on the time period and on the product level. The accuracy in the period 2016–2020 is better than in 2011–2015 and it is as follows for the different products: i) Level 2 ascending: 1.85 / 1.50 psu (in 2011–2015 / 2016–2020); Level 2 descending: 2.95 1.95 psu; ii) Level 3: 0.7 / 0.5 psu; and iii) Level 4: 0.6 / 0.4 psu.</p>