Abstract
Submesoscale air-sea interactions remain largely under-explored despite their potential role in shaping marine atmospheric boundary layer (MABL) dynamics. Using a high-resolution air-sea coupled numerical model, we investigated the atmospheric response to a submesoscale cold filament in the South China Sea, bounded by two sharp density fronts. The atmospheric response exhibits three primary features: (i) A pronounced shoaling of the MABL develops above the filament core, driven by depressed buoyancy fluxes associated with turbulent heat exchanges that are approximately half of those observed over warm mesoscale eddies. This thinning is accompanied by a decoupling of momentum exchange. (ii) A positive correlation between sea surface temperature (SST) gradients and surface wind divergence suggests that vertical turbulent mixing, rather than the pressure adjustment mechanism, governs the MABL adjustment above the oceanic submesoscale cold filaments. (iii) Two asymmetric secondary circulations form on either side of the filament, arising from the down-front wind orientation, as confirmed by sensitivity experiments. Momentum budget analysis reveals that vertical mixing dominates momentum tendencies in the lower MABL, while the Coriolis force term becomes increasingly important aloft. These findings provide new insights into how submesoscale oceanic features modulate atmospheric structure and surface fluxes, with implications for improving coupled model representation of boundary-layer processes.