Start
February 19, 2021 - 3:00 pm
End
February 19, 2021 - 4:00 pm
Categories
Convective Meteorology (Mesoscale Dynamics)Convective Meteorology (Mesoscale Dynamics) Seminar
Modeling CCN effects on Electrification within High and Low Precipitation Supercells
Jessica Blair
Friday, February 19th
3:00pm
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Cloud condensation nuclei (CCN) affect both the electric and dynamic evolution of storms, but the effects on storm electrification in different storm modes have not been thoroughly examined. We will detail the impacts of CCN in simulations of two very different supercells: the high-precipitation Geary, Oklahoma supercell storm from the Thunderstorm Electrification and Lightning Experiment (TELEX) on 29-30 May 2004, and the lower-precipitation Kimball, Nebraska supercell storm from the Stratosphere-Troposphere Experiment: Radiation, Aerosols, and Ozone-A (STERAO-A) on 10 July 1996. We ran simulations with five different CCN concentrations (100, 300, 500, 1000, and 2000 cm-3) in the Collaborative Model for Multi-scale Atmospheric Simulation (COMMAS), a three-dimensional cloud model with a bulk electrification scheme and a three-moment microphysics scheme with six hydrometeor types. The simulations provide details on storm dynamics, kinematics, and electrification that cannot be observed directly with a controlled change in a single variable, the CCN concentration
The CCN concentration of each model run significantly affected the storm dynamics, kinematics, and electrification in both storms. There were differences in net storm polarity, the location, timing and magnitude of net electrification with CCN concentrations. Similar patterns were observed in both case studies— very low CCN concentrations were found to have opposite polarity than that of higher CCN concentrations when we used the Saunders and Peck (1998) non-inductive charging scheme. A comparison with the Takahashi non-inductive charging scheme, which is more sensitive to changes in temperature, did not resolve similar polarity reversals in the net charge structure with CCN concentrations but did produce large changes in net charge magnitudes with time and altitude in each of the simulated storms with different CCN concentrations. Under both non-inductive electrification schemes, flash initiation totals were found to increase with increasing CCN concentrations, however the Takahashi scheme had significantly fewer net flash initiations than the Saunders and Peck scheme. The overall evolution of the storm also differed with CCN concentration. Delays in the initial onset of precipitation, suppression in the horizontal extent of storm, and weakening of the strength and extent of cold pools was observed at higher CCN concentrations.