Using satellite observations to evaluate model microphysical
representation of Arctic mixed-phase clouds
Abstract
Mixed-phase clouds play an important role in determining Arctic warming,
but are parametrized in models and difficult to constrain with
observations. We use two satellite-derived cloud phase metrics to
investigate the vertical structure of Arctic clouds in two global
climate models that use the Community Atmosphere Model version 6 (CAM6)
atmospheric component. We report a model error limiting ice nucleation,
produce a set of Arctic-constrained model runs by adjusting model
microphysical variables to match the cloud phase metrics, and evaluate
cloud feedbacks for all simulations. Models in this small ensemble
uniformly overestimate total cloud fraction in the summer, but have
variable representation of cloud fraction and phase in the winter and
spring. By relating modelled cloud phase metrics and changes in
low-level liquid cloud amount under warming to longwave cloud feedback,
we show that mixed-phase processes mediate the Arctic climate by
modifying how wintertime and springtime clouds respond to warming.