Resolution control on SST–precipitation coupling in Western Boundary Currents

Western Boundary Currents (WBCs) are key regions of air–sea interactions, where oceanic variability can strongly influence the atmospheric circulation and precipitation. Despite growing observational evidence of local covariability between SST and precipitation anomalies along these currents, climate models still differ markedly in their ability to represent this coupling. In particular, it remains unclear which elements of model resolution and physical parameterizations control the emergence, strength, and spatial organization of the SST–precipitation relationship.

Here, we examine the sensitivity of local SST–precipitation covariability to oceanic and atmospheric resolution and to the representation of moist convection. We analyze a coordinated hierarchy of global simulations, including coarse-resolution CMIP6 models, eddy-permitting and eddy-resolving configurations of ICON and EC-Earth3P, a convection-permitting ICON experiment, and atmosphere-only simulations forced with mesoscale-resolving and smoothed SSTs. Using a consistent diagnostic framework across four major WBC systems, we assess how model design shapes both the amplitude and structure of the atmospheric response.

Our results show that resolving mesoscale ocean variability is essential for reproducing a localized precipitation response to SST anomalies. However, increasing resolution alone does not guarantee realism: high-resolution configurations often produce overly broad coupling, while disabling the convective parameterization weakens the response despite fine grid spacing. These findings highlight the need for a physically consistent treatment of ocean mesoscale dynamics and atmospheric convection to capture realistic air–sea coupling along WBCs, with implications for simulating extratropical precipitation and storm-track variability.