89th American Meteorological Society Annual Meeting

Tuesday, 13 January 2009
Microphysics complexity effects on storm evolution and electrification
Hall 5 (Phoenix Convention Center)
Blake J. Allen, Pittsburg State University, Pittsburg, KS; and E. R. Mansell
Poster PDF (1.9 MB)
This study analyzed the electrical, microphysical and kinematic effects of predicting number concentration in addition to mass in a mixed-phase, bulk microphysics scheme. The microphysics scheme includes 5 hydrometeor categories: cloud droplets, rain, cloud ice, snow, and graupel. In a set of multicell storm simulations, number concentration prediction was enabled for additional hydrometeor(s) in each experiment as follows: (1) No concentrations, (2) Cloud ice concentration only, (3) Cloud droplet concentration added, (4) Rain concentration added, and (5) Snow and graupel concentrations added. Bulk graupel particle density was also predicted for all cases.

The prediction of cloud ice concentration had a significant effect on electrification but caused little change in the kinematics compared to the single moment case. The addition of cloud droplet concentration was found to delay the development of the initial updraft by 2 to 3 minutes, and the addition of rain concentration had a significant effect on the storm's reflectivity structure. Storm electrification was quite sensitive to changes in the microphysics, with differences in the timing of graupel development between model runs leading to differences in the early electrification of the storm, and with differences in the number concentration of cloud ice between model runs influencing the rates of charge separation throughout the time simulated. A primary implication is that predictability is highly dependent on model physics, particularly in the weakly-sheared environment used for this study.

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