Sensitivity of idealized mixed-phase stratocumulus to climate perturbations

Abstract

Large eddy simulations (LES) that explicitly resolve boundary layer (BL) turbulence and clouds are used to explore the sensitivity of idealized Arctic BL clouds to climate perturbations. The LES focus on conditions resembling springtime, when surface heat fluxes over sea ice are weak, and the cloud radiative effect is dominated by the longwave effect. In the LES, the condensed water path increases with BL temperature and free‐tropospheric relative humidity, but it decreases with inversion strength. The dependencies of cloud properties on environmental variables exhibited by the LES can largely be reproduced by a mixed‐layer model. Mixed‐layer model analysis shows that the liquid water path increases with warming because the liquid water gradient increase under warming overcompensates for geometric cloud thinning. This response contrasts with the response of subtropical stratocumulus to warming, whose liquid water path decreases as the clouds thin geometrically under warming. The results suggest that methods used to explain the response of lower‐latitude BL clouds to climate change can also elucidate changes in idealized Arctic BL clouds, although subtropical and Arctic clouds occupy different thermodynamic regimes.