P2.89

Enhanced ZDR signature above melting layer

Jelena Andric, CIMMS/Univ. of Oklahoma, Norman, OK; and D. S. Zrnic, J. M. Straka, and V. M. Melnikov

We are presenting polarimetric radar data of winter stratiform cloud, obtained with S-band radar, located in Norman, OK. Collected data offer insight into poorly investigated bulk properties of ice crystals. The vertical profiles of polarimetric variables (reflectivity, Z; differential reflectivity Z_DR; cross correlation coefficient, ρ_hv) are examined. Near zero values of Z_DR at the cloud top suggest the presence of nearly spherical particles. From a cloud top downward, Z_DR increases up to the maximum of 2.5 dB, at approximately 4.5 km. These values suggest the presence of horizontally oriented plate like crystals. Enhanced Z_DR is followed by decreasing of ρ_hv. Also, a slightly increased vertical gradient of Z is observed. Z_DR decreases quite rapidly below 4.5 km, where snow aggregates are expected to be dominant. The focus is on the nature of the enhanced Z_DR signature. Since Z_DR is strongly dependent on density of particles, it is important to know the growth process of ice crystals at the enhanced Z_DR level. One dimensional model of ice crystal growth, which includes nucleation process, deposition, riming and aggregation, is used in an attempt to replicate the Z_DR signature that resembles the observed one.

  Extended Abstract (456K)

Poster Session 2, Cloud Physics Poster Session II
Wednesday, 30 June 2010, 5:30 PM-8:30 PM, Exhibit Hall

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