Evaluation of a new mixed‐phase cloud microphysics parameterization with CAM3 single‐column model and M‐PACE observations

Abstract

Most global climate models generally prescribe the partitioning of condensed water into cloud droplets and cloud ice in mixed‐phase clouds according to a temperature‐dependent function, which affects modeled cloud phase, cloud lifetime and radiative properties. This study evaluates a new mixed‐phase cloud microphysics parameterization (for ice nucleation and water vapor deposition) against the Atmospheric Radiation Measurement (ARM) Mixed‐phase Arctic Cloud Experiment (M‐PACE) observations using the NCAR Community Atmospheric Model Version 3 (CAM3) single column model (SCAM). It is shown that SCAM with the new scheme produces a more realistic simulation of the cloud phase structure and the partitioning of condensed water into liquid droplets against observations during the M‐PACE than the standard SCAM. A sensitivity test indicates that ice number concentration could play an important role in the simulated mixed‐phase cloud microphysics, and therefore needs to be realistically represented in global climate models.