Dual-polarization Doppler Radar Analysis of the Vertical Microphysical and Kinematic Structure of Northeastern U.S. Coastal Winter Storms

The last several winters have brought an onslaught of high-impact coastal winter storms in the northeastern United States. These debilitating “Nor'easters” can bring heavy snow, mixed-phase precipitation, strong winds, and coastal flooding, disrupting transportation, aviation, commerce, and ultimately put property and lives at risk. Yet, these impacts remain poorly forecast in numerical weather prediction models, in part due to uncertainties in physical parameterizations used in those models. Thus, detailed observations of physical processes are needed to constrain models.

Quasi-vertical profiles (QVPs) of the Doppler and polarimetric variables from WSR-88D radars – a new approach to analyzing and displaying these data – are used to investigate the vertical microphysical and kinematic structure of 2013-2015 Nor'easters. Such QVPs are combined with mesoscale model analyses and surface observations to characterize precipitation processes throughout the storm lifetimes. Results demonstrate that enhanced surface snowfall rates and snow-to-liquid ratios are linked with dendritic growth zones aloft, and that these regions of vigorous depositional growth are associated with enhanced vertical motion near the -15 °C level. The implications of such microphysical and kinematic observations for critical evaluation of mesoscale model parameterizations and ultimately for data assimilation will be discussed.