Abstract

On the night of 19 April 1994 coordinated University of North Dakota Citation aircraft and University of Utah polarization lidar data were collected from a lunar corona-producing high altitude cirrus cloud from the DOE Cloud and Radiation Testbed (CART) site near Lamont, OK. In agreement with earlier lidar studies (Sassen 1991), relatively strong laser depolarization was noted near the frigid (-70°C) cloud top, which was located slightly above the tropopause. Although the two-ringed corona was not successfully photographed, the radius of the first red ring was estimated to be 2.5 moon diameters (~2.5°). The mean in situ ice crystal sizes derived from the FSSP measurements (the particles were too small to be effectively sampled by the 2D-C ice crystal probe) varied from 20-25 μm in diameter, which is consistent with the estimated size of the corona using simplified diffraction theory. Ice crystal concentrations were atypically high for cirrus, ranging between 400-500 cm^-3. The habits of these ice crystals are currently being examined photomicrographically using the plastic replicas of the particles captured by impaction during the aircraft mission.

© 1997 Optical Society of America