Improved diurnal variability forecast of ocean surface temperature through community model development

• Main Authors: Karagali, Ioanna, She, Jun, Høyer, Jacob L.
• Format: Conference Object
• Language: English
• Published: 2018
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/climate_action; SDG 13 - Climate Action; North Atlantic
• Online Access: https://orbit.dtu.dk/en/publications/8dc31b4f-fe67-4b08-b5d7-e91468aca1c9; https://backend.orbit.dtu.dk/ws/files/203285868/improved_diu.pdf

During daytime, under low winds and due to solar heating, the skin and sub-skin temperatures, typically measured by satellites can increase by several degrees compared to the foundation temperature. Diurnal variability has been observed in the Mediterranean [5], western North Atlantic [1] and the global ocean [2,3] from in situ and satellite observations. Diurnal heating has been reported at higher latitudes [4] and an extended study to characterise the regional patterns of diurnal SST variability over the Atlantic Ocean and the European Seas [5], showed frequent occurrences of diurnal warming events reaching several degrees, in the Baltic Sea. Nonetheless, diurnal SST variability it is not fully resolved by ocean and coupled oceanatmosphere models. Although some of the important diurnal variability and cool skin effects [6] have been shown to be reproducible [7], the vertical grid resolution of the models is of meter-scale. In addition, regional CMEMS ocean forecasting systems only assimilate a single SST field per day, representative of night-time conditions when the water column is well mixed and thus, no diurnal signal is present. Such simplification of the SST has been reported to cause biases in the estimated surface fluxes [8,9]. The implications associated with the lack of a properly resolved SST daily cycle in atmospheric, oceanic and climate models have been quantified in terms of heat budget errors mostly in the Tropics. Heat flux errors associated with the warm layer development were reported in [9] to range between 10 and 50 Wm-2. In regions with diurnal warm layer formation, [10] reported an annual mean surface flux out of the ocean that reached up to 9 Wm-2. In addition, strong SST diurnal signals can complicate the assimilation of SST fields in ocean and atmospheric models, the derivation of atmospheric correction algorithms for satellite radiometers and the merging of satellite SST from different sensors [11]. Not accounting for the daily SST variability can cause biases in the prediction and ...