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Published September 2019 | Published
Journal Article Open

Forty-five years of oceanographic and meteorological observations at a coastal station in the NW Mediterranean: a ground truth for satellite observations

Salat, Jordi ORCID icon
Pascual, Josep
Flexas, Mar ORCID icon
Chin, Toshio Michael
Vazquez-Cuervo, Josep

Abstract

Marine and atmospheric parameters, including temperature observations from surface to 80 m (at 6 depths) are measured since September 1973 on a higher-than-weekly frequency, at a coastal station 4 km offshore L'Estartit (Costa Brava; NW Mediterranean). This constitutes the longest available uninterrupted oceanographic time series in the Mediterranean Sea. The present contribution focuses on observed climatic trends in temperature (°C/year) of air (AT; 0.05), sea surface (SST; 0.03), sea at 80 m depth (S80T; 0.02) and sea level (SL; 3.1 mm/year) as well as comparison with trends estimated from coincident high-resolution satellite data. The trending evolution is not uniform across seasons, being significantly higher in spring for both AT and SST, while in autumn for S80T. Other climatological results are a stratification increase (0.02 °C/year in summer temperature difference between 20 m (S20T) and S80T), trends in summer conditions at sea (when S20T > 18 °C), estimated as 0.5 and 0.9 days/year for the starting day and period respectively, and a decreasing trend of nearly 2 days/year in the period of conditions favourable for marine evaporation (when AT < SST). This last trend may be related to the observed decrease of coastal precipitation in spring. The long-term consistency in the in situ SST measurements presents an opportunity to validate the multi-decadal trends. The good agreement for 2013–2018 (RMS 0.5–0.6, bias − 0.1 to − 0.2; trends of 0.09 °C/year in situ vs. 0.06 to 0.08 °C/year from satellite) allows considering this observational site as ground truth for satellite observations and a monitoring site for climate change.

Additional Information

© 2019 The Author(s). This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. First Online: 09 August 2019. This article is part of the Topical Collection on the 50th International Liège Colloquium on Ocean Dynamics, Liège, Belgium, 28 May to 1 June 2018. The authors acknowledge technical support from the Institut de Ciències del Mar (ICM/CSIC) to maintain the time series of L'Estartit. MF acknowledges support from the National Aeronautics and Space Administration (NASA) through grant number NNX15AG42G. The work by TMC and JV was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the NASA. The authors also thank the always warm atmosphere found in the Liège Colloquium and the suggestions received from the participants. The advice from the Editor and the reviews from three anonymous referees have greatly contributed to improve the original manuscript to reach the final version of this paper. The help of Dr. C. Behrens from PANGAEA was crucial to facilitate data publication in that repository.

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Identifiers Funding Dates
Created:
August 22, 2023
Modified:
October 18, 2023