The effects of ice nucleation parameterizations in GFDL climate model

We incorporated a temperature, dust, and sea spray aerosol-dependent ice nucleation parameterization in the recently developed GFDL AM4-MG2 framework, and refer to this new configuration as AM4-MG2-new. The major difference of the ice nucleation parameterizations in AM4-MG2-new and AM4-MG2 is the inclusion of sea spray aerosol as ice nucleating particles (INPs). Then we conducted AMIP (Atmospheric Model Intercomparison Project) mode simulation with AM4-MG2-new. It turns out that AM4-MG2-new produces mean model climate comparable to AM4-MG2, for example, similar cloud radiative and precipitation fields, but different cloud water phase partitioning or supercooled cloud fractions, especially over the mid-high latitudes where mixed-phase clouds (clouds that consist of both liquid and ice) are prevalent. The cloud-phase feedback could in turn impact the estimate of climate sensitivity. The results suggest that ice nucleation parameterizations, which have large uncertainties, have important impacts on climate sensitivity.