Sensitivity of WACCM/CARMA simulations of polar mesospheric clouds to gravity wave and microphysics parameterizations

We use WACCM/CARMA to explore the sensitivity of simulations of polar mesospheric clouds (PMCs) to changes in the parameters and processes that impact the cloud microphysics. WACCM/CARMA is a three- dimensional chemistry climate model based upon the Whole-Atmosphere Community Climate Model (WACCM) with sectional microphysics from the Community Aerosol and Radiation Model for Atmospheres (CARMA). We look at the response of the model to changes in the gravity wave parameterization, the ice particle nucleation scheme and the specification of radiative heating of the cloud particles. These results are compared with cloud properties retrieved from the Solar Occultation for Ice Experiment (SOFIE) and the Cloud Imaging and Particle Size Experiment (CIPS) instruments from the Aeronomy of Ice in the Mesosphere (AIM) mission. We find that the simulated cloud properties generally agree well with both SOFIE and CIPS observations and are very sensitive to the gravity wave parameterization. We see similar results for a variety of nucleation parameters and find radiative heating to be necessary to get a mid-season reduction in PMCs that is seen in the observations.