Poster Session P2.89 Enhanced ZDR signature above melting layer

Wednesday, 30 June 2010
Exhibit Hall (DoubleTree by Hilton Portland)
Jelena Andric, CIMMS/Univ. of Oklahoma, Norman, OK; and D. S. Zrnic, J. M. Straka, and V. M. Melnikov

Handout (448.2 kB)

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 ZDR; cross correlation coefficient, ρhv) are examined. Near zero values of ZDR at the cloud top suggest the presence of nearly spherical particles. From a cloud top downward, ZDR 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 ZDR is followed by decreasing of ρhv. Also, a slightly increased vertical gradient of Z is observed. ZDR decreases quite rapidly below 4.5 km, where snow aggregates are expected to be dominant. The focus is on the nature of the enhanced ZDR signature. Since ZDR is strongly dependent on density of particles, it is important to know the growth process of ice crystals at the enhanced ZDR level. One dimensional model of ice crystal growth, which includes nucleation process, deposition, riming and aggregation, is used in an attempt to replicate the ZDR signature that resembles the observed one.
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