Preprints
https://doi.org/10.5194/gmd-2024-13
https://doi.org/10.5194/gmd-2024-13
Submitted as: development and technical paper
 | 
30 Jan 2024
Submitted as: development and technical paper |  | 30 Jan 2024
Status: this preprint is currently under review for the journal GMD.

Skin Sea Surface Temperature schemes in coupled ocean-atmosphere modeling: the impact of chlorophyll-interactive e-folding depth

Vincenzo de Toma, Daniele Ciani, Yassmin Hesham, Chunxue Yang, Vincenzo Artale, Andrea Pisano, Davide Cavaliere, Rosalia Santoleri, and Andrea Storto

Abstract. In this paper, we explore different prognostic methods to account for skin sea surface temperature diurnal variations in a coupled ocean-atmosphere regional model of the Mediterranean Sea. Our aim is to characterize the sensitivity of the considered methods with respect to the underlying assumption of how the solar radiation shapes the warm layer of the ocean. All existing methods truncate solar transmission coefficient at a constant warm layer reference depth; instead, we develop a new scheme where this latter is estimated from a chlorophyll dataset as the e-folding depth of solar transmission. This allows spatial and temporal variations of the warm layer extent to depend on seawater transparency. Comparison against satellite data shows that our new scheme improves the diurnal signal especially during winter, spring, and autumn, with an averaged bias on monthly scales year-round smaller than 0.1 K. In April, when most of the drifters measurements are available, the new scheme mitigates the bias during nighttime, keeping it positive but smaller than 0.12 K during the rest of the monthly-averaged day. The new scheme implemented within the ocean model improves the old one by about 0.1 K, particularly during June. All the methods considered here showed differences with respect to objectively analyzed profiles confined between 0.5 K during winter and 1 K in summer for both the eastern and the western Mediterranean regions, especially over the uppermost 60 m. Overall, the surface net total heat flux shows that the use of a skin SST parametrization brings the budget about 1.5 W/m2 closer to zero on an annual basis, despite all simulations showing an annual net heat loss from the ocean to the atmosphere. Our “chlorophyll-interactive” method proved to be an effective enhancement of existing methods, its strength relying on an improved physical consistence with the solar extinction implemented in the ocean component.

Vincenzo de Toma, Daniele Ciani, Yassmin Hesham, Chunxue Yang, Vincenzo Artale, Andrea Pisano, Davide Cavaliere, Rosalia Santoleri, and Andrea Storto

Status: open (until 06 Apr 2024)

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Vincenzo de Toma, Daniele Ciani, Yassmin Hesham, Chunxue Yang, Vincenzo Artale, Andrea Pisano, Davide Cavaliere, Rosalia Santoleri, and Andrea Storto
Vincenzo de Toma, Daniele Ciani, Yassmin Hesham, Chunxue Yang, Vincenzo Artale, Andrea Pisano, Davide Cavaliere, Rosalia Santoleri, and Andrea Storto

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Short summary
This study explores methods to reconstruct diurnal variations in skin sea surface temperature in a model of the Mediterranean Sea. Our new approach, considering chlorophyll concentration, enhances spatial and temporal variations in the warm layer. Comparative analysis shows context-dependent improvements. The proposed "chlorophyll-interactive" method brings the surface net total heat flux closer to zero annually, despite a net heat loss from the ocean to the atmosphere.