Evaluation of cloud liquid water content retrievals using dual-wavelength radar measurements
Authors
zeen zhu — Brookhaven National Laboratory
Pavlos Kollias — Stony Brook University
Eugene E. Clothiaux — Pennsylvania State University
Dong Huang — NASA - Goddard Space Flight Center
Edward Luke — Brookhaven National Laboratory
Robert Wood — University of Washington
Category
Microphysics (cloud, aerosol and/or precipitation)
Description
Measurements of cloud liquid water content (LWC) are important for understanding cloud microphysical structure and variability, and for entrainment and precipitation studies. Several algorithms have been proposed for retrieving the LWC in warm clouds (e.g. radar-only, radar-radiometer, dual-wavelength radar). The dual-wavelength ratio (DWR) radar-based technique requires well-matched radar observations at two wavelengths, as those provided by the Scanning ARM Cloud Radars (SACR’s) and the use of differential radar reflectivity measurements for retrieving the profile of LWC in clouds. The DWR technique is very promising because it makes no assumptions about the vertical structure of the LWC profile, it’s not affected by the presence of drizzle and provides LWP estimates even when the microwave radiometer measurements are obstructed by surface precipitation. The DWR technique is applied to warm cloud observations at the ARM Eastern North Atlantic (ENA) site during periods when the SACR is vertically pointing. Two variants of the DWR method are use: one based on optimal estimation theory (Huang et al., 2009) and another based on a DWR fitting function. The performance of the DWR-based LWC retrievals is discussed, especially in the case of precipitating shallow cumulus clouds.
