Tropical Ocean Evaporation‐Temperature Sensitivity to Surface Radiative Property Perturbations in Fully Coupled CESM2

Abstract Tropical ocean evaporation is the dominant source of moisture for global precipitation. However, the dependence of evaporation‐temperature sensitivity on ocean surface radiative properties has not been quantified in the fully coupled modeling framework. This study developed physically based ocean surface albedo (OSA) parameterizations that incorporate multiple governing processes, along with a spectrally resolved graybody effective ocean surface emissivity (OSE). These formulations were implemented as perturbation experiments within the fully coupled Community Earth System Model version 2 (CESM2), and the resulting fractional changes in evaporation‐temperature sensitivity were decomposed into individual contributions via the ocean surface energy budget framework. OSA perturbations drive the large increase in fractional evaporation–temperature sensitivity. The resulting surface warming and atmospheric moistening elevate downward longwave radiation, with enhanced low‐cloud coverage further amplifying this effect. These positive contributions are partially offset by stronger surface thermal‐emission damping and reduced incident solar flux associated with increased cloudiness. OSE modification alone produces negligible changes in sensitivity, as reduced emissivity largely compensates for the weakened thermal damping within the longwave budget. The contrasting responses reveal that OSA adjustments exert substantially greater influence on evaporation‐temperature sensitivity than OSE modifications, operating through both direct shortwave absorption and indirect atmospheric radiative feedbacks. These findings carry practical implications for future Earth system model development. Refined OSA treatments and the associated shortwave radiative budget will likely demand more extensive model retuning, whereas OSE improvements can be incorporated with comparatively less effort.