92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Tuesday, 24 January 2012: 2:45 PM
Dual-Polarization Observations of Vortices and Cellular Convection within Lake-Effect Snow Bands
Room 239 (New Orleans Convention Center )
Timothy R. Cermak, Univ. of Illinois, Urbana, IL; and J. Frame and E. T. Ahasic
Manuscript (1.1 MB)

In the winter of 2010-2011, a Doppler on Wheels (DOW) radar acquired dual-polarization observations of long-lake axis parallel lake-effect snow bands over Lake Ontario. The dual-polarization parameters obtained during these deployments include differential reflectivity (ZDR), specific differential phase (KDP), and the cross-correlation coefficient between the horizontally and vertically polarized waves (ρhv). Previous dual-polarization observations of wintertime precipitation situations, especially lake-effect snow events, are limited, as the majority of past observations were taken during warm-season convective events. During these lake-effect snow deployments, the DOW observed embedded vortices, ranging in size from 500 m to 10 km, in addition to both banded and cellular convection. This study concentrates on the possible relationship between the presence of these features and the dual-polarization fields, as well as the impacts these features have on the local structure and intensity of the snow bands. In most cases during which cellular convection was present, the ZDR reached greater values in the convective cells than in other regions of the band. It is anticipated that the convective cells contain hydrometeor types and distributions differing from those in the primary snow band. Higher ZDR values were also typically observed where vortices were located, though the location of ZDR maxima within the vortices varied. In most cases, the ZDR maxima were collocated with higher reflectivity in the hook signatures of the vortices, while in other cases the ZDR maxima were located near the center of the vortices, where local reflectivity was minimized. From these observations, it is projected that the embedded vortices locally affect hydrometeor type and distribution.

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