Determination of cloud phase from active and passive sensors during AWARE
Authors
Maria Paola Cadeddu — Argonne National Laboratory
Dan Lubin — Scripps Institution of Oceanography
Andrew M. Vogelmann — Brookhaven National Laboratory
Virendra Prakash Ghate — Argonne National Laboratory
Category
High-latitude clouds and aerosols
Description
The phase of Antarctic clouds impacts the amount of radiation reaching the Earth’s surface. It is therefore important to understand under which conditions clouds may transition from liquid to mixed phase, and to ice phase. During the AWARE campaign the ARM 2-channel microwave radiometer (MWR), G-band vapor radiometer (GVRP), and micropulse lidar (MPL) collected simultaneous data at the West Antarctic Ice Sheet (WAIS) and McMurdo sites. These instruments are sensitive in different ways to the amount of liquid water or ice in the clouds and, when combined, can provide important information on the cloud phase. A cloud mask was developed using the MPL at WAIS and the MPL and cloud radar at McMurdo. The cloud mask provides information on cloud boundaries, depolarization ratio, and reflectivity. In addition, the MWR, GVRP, and ceilometer were used to derive precipitable water vapor (PWV), cloud liquid water path (LWP), and low-resolution vertical profiles of humidity. The G-band channels have a residual sensitivity to atmospheric temperature in the first few kilometers; therefore, a secondary product of the retrieval is low-resolution temperature profiles adjusted to be consistent with the GVRP radiance measurements. Because of the low variability of the temperature profiles at the two sites, these adjusted profiles were used to estimate cloud temperature between radiosonde launches. In this work we examine average cloud temperature, in conjunction with cloud LWP, depolarization ratio, and reflectivity to gather information on prevalent cloud phase at the two sites.
