Ocean tidal cooling effect on summer sea fog over the Okhotsk Sea

Ocean tide is a periodic phenomenon of the rise and fall of the sea level that depends on the bathymetry and positions of the moon and sun relative to the earth. In the Okhotsk Sea, the ocean tide causes strong vertical mixing in the upper ocean, generating rich structures in summer SST with extraordinarily cold patches on Kashevarov Bank, along the Kuril Islands, northeast of the Terpeniya Peninsula, and inside Shelikhov Bay. The present study analyzes and synthesizes a suite of ship-board and satellite observations, and numerical simulations to investigate the ocean tidal cooling effect on summer sea fog over the Okhotsk Sea. Over the tide-induced cold patches, atmospheric stability increases, and surface wind weakens markedly possibly through suppressed atmospheric vertical mixing. Our analysis of ship-board observations reveals frequent sea-fog occurrence over the cold patches with a maximum exceeding 70% along the Kuril Islands in July-August. Numerical simulations with the Weather Research and Forecasting (WRF) model support that the cold patches cool air temperature, decelerates surface wind, and forms a strong surface inversion layer up to 0.5 km high, creating favorable conditions for sea fog occurrence. The WRF simulation without the tidal cooling effect reduces sea fog occurrence by more than 20% over cold patches, illustrating the importance of SST products for climate models.