Simulating Aerosol-Cloud Interaction Dynamics and Chemistry of the Optical Properties for Large-scale and Convective Ice Clouds

The aerosols-liquid cloud interactions are relatively better understood as well as parameterized, whereas the interaction between aerosols and ice-clouds is still in infancy, partly because aerosol-ice cloud interaction processes have not been well understood. Specifically, role of aerosols on ice-phase cloud nucleation processes and radiative properties of cold cirrus still have gaps in our understanding. Using the Liu and Penner (2005) ice-cloud parameterization for sulfates and black carbon, we simulated ice-cloud particle number concentration (IPNC) and effective radius (re) for both convective and large-scale clouds. As compared to observations, we simulated reasonable cloud water, but the effective radius was too large and IPNC was too small over Atmospheric Radiation measurement (ARM) sites and 14 other locations analyzed by Andrae (2008) comprising of some pristine and polluted environments. Some preliminary results using a simple calculation for ammonium sulfate released by freezing cloud droplets (CDs) reveal that the solution may lie in parameterizing ice-cloud nucleation by ammonium sulfate that is neglected in the original Liu and Penner parameterization. Another area of investigation is to sort lifting of cloud particles by fall velocity in deep convection leading to smaller particles getting lifted while larger CDs stay in the water cloud regimes.