Wednesday, 13 January 2016
Hall D/E ( New Orleans Ernest N. Morial Convention Center)
Mixed-phase clouds in the Arctic are highly influential within determining the surface radiation budget, yet are poorly understood. These clouds contain both liquid water droplets and ice crystals in the same volume, each with different impacts on the radiation budget. In order to study the surface budget, it is necessary to separate and analyze the properties from each phase. Using Ka-band zenith radar (KAZR) Doppler velocity spectra from the Atmospheric Radiation Measurement (ARM) Program North Slope of Alaska (NSA) site, we separated contributions from the cloud liquid drop and the ice precipitation modes based on a continuous wavelet transform and fuzzy logic techniques (Yu et al., 2014). Cloud liquid drop and precipitation reflectivities, vertical air motions, and reflectivity-weighted mean fall velocities are retrieved for 836 hours of observations of single-layer mixed-phase clouds from September to December, 2011 to 2014. Our analysis reveal a relationship between the maximum precipitation reflectivities and minimum cloud temperature similar to that of the temperature dependence of ice crystal vapor depositional mass growth reported by Chen and Lamb (1994). These findings could be the result of a temperature dependence of the ice crystal mass growth in the observed clouds, although other factors such as various scattering processes could also play a role. Additional results suggest a temperature dependence between maximum precipitation reflectivities and mean vertical velocities in mixed-phase clouds, revealing that clouds with temperatures between -20°C and -12°C were most likely to contain stronger downdrafts and larger ice particulates. However, future research is needed to validate these results as well as to achieve greater understanding of these influential clouds in the radiation budget.
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