Recent Results from Storm Electrification Modeling
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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
description
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. - PowerPoint PPT Presentation
Transcript of Recent Results from Storm Electrification Modeling
Recent Results from Storm Electrification Modeling
Edward MansellCIMMS/Univ. of Oklahoma/NSSL, Norman, OK
co-investigators Donald MacGorman, Conrad Ziegler National Severe Storms Laboratory, Norman, OK
Jerry Straka, Kristin KuhlmanUniversity of Oklahoma, School of Meteorology
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)
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)
Electrification Options:• Five noninductive charging
parameterizations (graupel-crystal):5. Brooks et. al (1997, AR)6. Saunders and Peck (1998, JGR)7. Saunders et al. (1991)/Helsdon et al. (2001)8. Gardiner et al. (1985)/Ziegler et al. (1991)9. Takahashi (1978,1984, JAS)
• Inductive charging (graupel-droplet) (Ziegler et al., 1991, JGR)
Noninductive Charge Separation
Before After
–
+
Inductive Charge Separation
Before After
E
Segment-by-segment development of
lightning channelsAdvantage: 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.
Stochastic Lightning Model:
−∇2φ=ρε
Lightning Propagation Grid
Positive leader
Negative leader
InitialBreakdown
Intracloud flash
Positive CG Flash
Negative CG flash
Small storm simulation (Florida)
Positiveleaders
Negativeleaders
InitialBreakdown
25 km
30 flashes in 1 hour
Supercell storm simulation (STEPS)
(K. Kuhlman)80 km
10,000 flashes in 3 hours
What effects does inductive charging have?(in the model, at least)
Look at a multicell storm with and without inductive charging.
Using Takahashi noninductive charge separation scheme:
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.
Charge density
No Inductive
Charge density
Noninductive charging rate Inductive charging rate
36 Min With Inductive
Decaying cell
New cell
Neg. Charge to graupel
Pos. Charge to graupel
NIC only NIC+IC
Graupel Mix. Rat.
Wind vectors
First cell decaying, new cell growing
Charge density Charge density
Noninductive charging rate Inductive charging rate
NIC only NIC+IC40 Min
New cell growing; recylcing graupel from old cell
Charge density Charge density
Noninductive charging rate Inductive charging rate
NIC only NIC+IC44 Min
New cell maturing; has ‘dipole’ charge structure
Charge density Charge density
Noninductive charging rate Inductive charging rate
NIC only NIC+IC48 Min
Mature cell; strong inductive chargingLPC
Charge density Charge density
Noninductive charging rate Inductive charging rate
NIC only NIC+IC52 Min
Second cell mature; flashes with LPC
Charge density Charge density
Noninductive charging rate Inductive charging rate
NIC only NIC+IC56 Min
Second cell decaying; third cell growing
Charge density Charge density
Noninductive charging rate Inductive charging rate
NIC only NIC+IC60 Min
Third cell explosive growth; recylces graupel
Charge density Charge density
Noninductive charging rate Inductive charging rate
NIC only NIC+IC64 Min
Strong inductive charging in third cell, -CG flashes
Time-height lightningNo inductive charging
With inductive charging
Positive leaders
Negative leaders
Lightning correlations
Positive CG flash
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)
Merci!Thank you!
Gracias!Danke!
Interrogations?Questions?¿Preguntas?
Fragen?
