Representation of Arctic Mixed-phase Clouds in Models (and why it matters...)

Hugh Morrison

National Center for Atmospheric Research

Recent observations in the Arctic indicate that mixed-phase clouds are common throughout the year. However, most climate and weather models fail to reproduce the observed frequency and persistence of these clouds, leading to substantial biases in the downwelling surface radiative fluxes and surface energy budget. Thus, it is argued that a correct treatment of mixed-phase clouds is needed for a realistic simulation of the Arctic climate, which appears to be undergoing rapid change. A new two-moment cloud microphysics scheme has been implemented into the MM5 and WRF weather prediction models to address this deficiency. Key factors impacting the ability of the models to simulate Arctic mixed-phase clouds will be discussed, as well as the impact of these clouds on other critical model components such as the radiative transfer, boundary layer and surface thermodynamics and atmospheric dynamics.