Investigating In Situ and Liquid Origin Cirrus Clouds from Subtropical and Extratropical Campaigns: PREDICT and HIPPO

Cirrus Clouds have been found to have a significant impact on the global radiative budget due to their widespread global coverage. It has been found more recently that the microphysical properties of cirrus clouds are affected by the origin of these clouds. Two types of cirrus clouds will be analyzed in this work - liquid origin cirrus clouds resulting from freezing of cloud droplets in mixed phase clouds, and in situ cirrus clouds forming ice from homogeneous freezing. Presently, the lack of understanding on distinguishing cirrus clouds from in situ and liquid origins based on in situ observations of microphysical characteristics and environmental dynamics is the motivation for this study. The focus of this study is analyzing and contrasting these two origins, by comparing in situ observations collected in the extratropical regions (i.e., part of the HIAPER Pole-to-Pole Observations global campaign (HIPPO 2009-11)), and the subtropical region (Pre-Depression Investigation of Cloud Systems in the Tropics (PREDICT 2010)). Investigation of thermodynamic conditions such as occurrences of ice supersaturation (ISS where relative humidity with respect to ice (RH_ice) > 100%), cloud microphysical characteristics such as ice crystal concentrations (N_ice) and size distributions (R_ice), as well as dynamical conditions such as vertical velocities will be analyzed at temperatures ≤ -40℃. To examine the convective impact, statistical analysis will be conducted on the relationship between vertical velocity and ISS occurrence frequency with a fixed ice water content (IWC) or N_ice. The distribution of RH_ice will be investigated in clear-sky and in-cloud conditions to examine the probability of heterogeneous and homogeneous freezing. Finally, magnitudes of N_ice and IWC with respect to vertical velocities with a fixed RH_ice will be examined. This study will provide insight into the differences between the in situ and liquid origin cirrus clouds microphysics and the factors contributing to their differences.