HR: 1340h
AN: A23C-0967    [Abstracts]
TI: Mixed-Phase Cloud Measurements with the University of Wisconsin High Spectral Resolution Lidar
AU: * Eloranta, E W
EM: eloranta@lidar.ssec.wisc.edu
AF: University of Wisconsin-Madison, 1225 W. Dayton, Madison, WI5 53706 United States
AB: It would appear that mixed-phase conditions should be short-lived because the coexistence of ice and water results in rapid crystals growth and droplet evaporation. However, observations show that super-cooled clouds are often mixed-phase and long-lived. Ice crystal precipitation helps to maintain these clouds by removing ice from regions containing water. Thus, it is important to understand the evolution of ice crystal particle size and fall velocity in mixed-phase clouds. The ratio of the lidar and radar cross sections data can be used to measure the effective size of cloud and precipitation particles. Unfortunately, attenuation and multiple scattering make it difficult to measure the lidar scattering cross section. Standard lidar data does not contain sufficient information to correct for attenuation without the use of poorly supported assumptions. The multiply scattered signal is dependent on particle size and is often comparable in magnitude to the singly scattered signal. As a result, past lidar-radar particle size measurements have required use of complicated iterative solutions(Donovan and Lammeren, JGR, 106, Nov 16, 2001, pp 27425) These problems are avoided when using data from the University of Wisconsin Arctic High Spectral Resolution Lidar(AHSRL). This lidar provides robustly calibrated measurements of the backscatter cross section, scattering cross section and depolarization. Depolarization allows easy discrimination between ice and water clouds. Furthermore, the lidar receiver accepts light from a very small angular field-of-view greatly limiting multiply scattered signals. The AHSRL was operated at the North Slope site of the Atmospheric Radiation Measurement(ARM) program as part of the Mixed Phase Arctic Cloud Experiment(MPACE) and is currently operating in the high Arctic at Eureka, Canada (79.94N, 85.56W) as part of the NOAA SEARCH program. In both cases the lidar was located with a 35 GHz cloud radar. This paper presents measurements of cloud height, cloud phase, and lidar-radar particle size measurements derived during the MPACE experiment. Data relating radar measured particle fall velocities to particle size and preliminary data from the Eureka deployment will also be presented. In parallel with this effort we are adapting the University of Wisconsin Numerical Weather Model to study arctic cloud processes. This model predicts the evolution of particle sizes and morphologies. The lidar-radar measurements will be used evaluate the cloud physics package in this model.
UR: http://lidar.ssec.wisc.edu
DE: 0320 Cloud physics and chemistry
DE: 0321 Cloud/radiation interaction
DE: 0394 Instruments and techniques
DE: 3310 Clouds and cloud feedbacks
DE: 3349 Polar meteorology
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005