Wednesday, 7 November 2012
Symphony III and Foyer (Loews Vanderbilt Hotel)
Maximizing the accuracy of kinematical supercell analyses, and appropriately characterizing the uncertainty in ensuing conclusions about storm structure and processes, requires thorough knowledge of the error characteristics of different retrieval techniques under different observational scenarios. Using storm-scale mobile radar observations of a tornadic supercell, this study examines the impacts on ensemble Kalman filter (EnKF) wind analyses of the number of available radars (one or two), uncertainty in the model-initialization sounding, using a double- vs. single-moment microphysical parameterization scheme, and assimilating reflectivity observations. The relative accuracy of wind retrievals obtained using dual-Doppler analysis and 1- and 2-radar EnKF analysis is also explored. The results generally reinforce the findings of a previous study that used observing system simulation experiments to explore similar issues. Both studies suggest that single-radar EnKF wind analyses can be very useful once enough data have been assimilated, but that subsequent analyses that operate on the retrieved wind field gradients should be interpreted with caution. In the present study, severe errors appear to occur in parcel trajectories and Lagrangian circulation time series computed from single-radar EnKF analyses, imperiling interpretation of the underlying dynamics. This result strongly suggests that dual- and multiple-Doppler radar deployment strategies continue to be used in mobile field campaigns.
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