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Recent Results from Storm Electrification Modeling

Recent Results from Storm Electrification Modeling. Edward Mansell CIMMS/Univ. of Oklahoma/NSSL, Norman, OK co-investigators Donald MacGorman, Conrad Ziegler National Severe Storms Laboratory, Norman, OK Jerry Straka, Kristin Kuhlman University of Oklahoma, School of Meteorology.

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Recent Results from Storm Electrification Modeling

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  1. Recent Results from Storm Electrification Modeling Edward Mansell CIMMS/Univ. of Oklahoma/NSSL, Norman, OK co-investigators Donald MacGorman, Conrad Ziegler National Severe Storms Laboratory, Norman, OK Jerry Straka, Kristin Kuhlman University of Oklahoma, School of Meteorology

  2. Objectives: • Study electrification of thunderstorms • Examine differences in lightning for a spectrum of severe storms (supercell and non-supercell) • Compare and evaluate charge separation parameterizations • Investigate conditions for Cloud-to-ground (CG) lightning (especially +CG)

  3. Model Features: • Micophysics parameterization has 12 hydrometeor categories (bulk): • 2 Liquid: cloud droplets, rain • 10 Ice: cloud ice (columns, plates, rimed), snow (aggregates), frozen drops, 3 graupel densities, 2 hail size ranges • Explicit treatment of small ion processes (attachment, diffusion, corona emission at ground) • 3-D Branched lightning (Mansell et al. 2002)

  4. Electrification Options: • Five noninductive charging parameterizations (graupel-crystal): • Brooks et. al (1997, AR) • Saunders and Peck (1998, JGR) • Saunders et al. (1991)/Helsdon et al. (2001) • Gardiner et al. (1985)/Ziegler et al. (1991) • Takahashi (1978,1984, JAS) • Inductive charging (graupel-droplet) (Ziegler et al., 1991, JGR)

  5. + – After Noninductive Charge Separation Before

  6. q E After Inductive Charge Separation Before

  7. Stochastic Lightning Model: Segment-by-segment development of lightning channels Advantage: Effect of charge carried by channels on lightning propagation is included by recalculating the electric field via Poisson’s equation: Disadvantage: Can become computationally expensive for high flash rates.

  8. Initial Breakdown Lightning Propagation Grid Negative leader Positive leader

  9. Intracloud flash

  10. Positive CG Flash

  11. Negative CG flash

  12. Small storm simulation (Florida) Positive leaders Initial Breakdown Negative leaders 30 flashes in 1 hour 25 km

  13. Supercell storm simulation (STEPS) 10,000 flashes in 3 hours 80 km (K. Kuhlman)

  14. Severe Bow Echo Storm 70,000 flashes in 4 hours 140 km (J. Straka)

  15. What effects does inductive charging have? (in the model, at least) Look at a multicell storm with and without inductive charging.

  16. Using Takahashi noninductive charge separation scheme:

  17. Environment is for a continental storm. High CCN concentration shuts off warm rain process, so the initial precipitation develops from ice crystals. Inductive charging causes Lower Positive Charge region, resulting in negative CG flashes.

  18. 36 Min First cell decaying, new cell growing Neg. Charge to graupel Pos. Charge to graupel No Inductive With Inductive NIC only NIC+IC Decaying cell New cell Charge density Charge density Wind vectors Graupel Mix. Rat. Inductive charging rate Noninductive charging rate

  19. 40 Min New cell growing; recylcing graupel from old cell NIC only NIC+IC Charge density Charge density Inductive charging rate Noninductive charging rate

  20. 44 Min New cell maturing; has ‘dipole’ charge structure NIC only NIC+IC Charge density Charge density Inductive charging rate Noninductive charging rate

  21. 48 Min Mature cell; strong inductive chargingLPC NIC only NIC+IC Charge density Charge density Inductive charging rate Noninductive charging rate

  22. 52 Min Second cell mature; flashes with LPC NIC only NIC+IC Charge density Charge density Inductive charging rate Noninductive charging rate

  23. 56 Min Second cell decaying; third cell growing NIC only NIC+IC Charge density Charge density Inductive charging rate Noninductive charging rate

  24. 60 Min Third cell explosive growth; recylces graupel NIC only NIC+IC Charge density Charge density Inductive charging rate Noninductive charging rate

  25. 64 Min Strong inductive charging in third cell, -CG flashes NIC only NIC+IC Charge density Charge density Inductive charging rate Noninductive charging rate

  26. Positive leaders Negative leaders Time-height lightning No inductive charging With inductive charging

  27. Lightning correlations

  28. Positive CG flash

  29. Conclusions • Wide range of storms can be simulated • Possible importance of Inductive Graupel-droplet charging for lower positive charge development. • CG time-delay potentially related to graupel recycling time. • Correlations between lightning flash rates (IC/CG) and storm properties (e.g. graupel mass, updraft volume)

  30. Merci!Thank you!Gracias!Danke!Interrogations?Questions?¿Preguntas?Fragen?

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