Lidar characterization of cloud liquid water content and effective droplet diameter

Supercooled cloud and precipitation water droplets constitute a safety hazard to aviation. Concerned agencies are funding research on methods of remotely sensing the icing potential of such clouds and precipitation. The parameters needed are the temperature, the liquid water content (LWC) and the average droplet size. We report here on preliminary results obtained with a multiple-field-of-view (MFOV) lidar in an experimental program carried out at Mount Washington during April 1999. The MFOV technique consists in the measurement of the forward multiple scattering contributions to lidar returns coupled with a solution method that makes use of this additional information to calculate the extinction coefficient and the effective droplet diameter as the dependent functions, and the LWC as a by-product. The paper describes the MFOV retrieval method and gives sample results obtained in the Mount Washington experiment. The retrieved solutions demonstrate the lidar capability of remotely sensing droplet size and LWC: profiles of clouds and precipitation. Solution accuracy is determined to be 30-40% but the analysis of the data from all fielded sensors will be needed to validate these numbers.