Investigating ice initiation in tropical cumulus using airborne polarimetric radar and lidar: preliminary results from ICE-T

Heterogenous ice initiation, particularly at relatively warm temperatures, has long eluded comprehensive understanding despite decades of research. Here we present initial analyses of observations from the Wyoming Cloud Radar and the Wyoming Cloud Lidar during the ICE-T field campaign. The ICE-T field campaign, to be conducted in the Caribbean in July 2011, will focus on ice initiation in tropical Cu with cloud top temperatures around -10 C.

ICE-T will feature a unique combination of airborne remote sensors and in situ cloud probes deployed on the NSF/NCAR C-130. Remote sensing instruments include: up- and downward-looking versions of the Wyoming Cloud Lidar (WCL), plus the Wyoming Cloud Radar (WCR) in a configuration combining a single upward looking beam combined with a pair of downward-looking beams. The WCL will be used to document the boundaries of the visible cloud, providing context critical for interpretation of the WCR-measured radar reflectivities. The depolarization capabilities of the WCL will be used to identify both dust aerosol and ice crystal detection outside boundaries of the visible cloud (e.g. seeding from above or from previously detrained cloud elements).

The WCR configuration on the C-130 has been modified to so that the downward-slanted beam will have dual-pol capabilities. In addition to the 60 deg elevation angle of the down-slant beam, the linear polarization components have been rotated 45 with respect to the horizon so as to induce a LDR signature from both plate and needlelike crystals, while simultaneously decreasing the sensitivity to the distribution of canting angles. This combination of radar and lidar is intended to provide a uniquely detailed glimpse into the occurrence and prevalence of ice within tropical Cu.