1. and NM Tech team & many HyMeX participants
Explicit simulations in a mesoscale model of electrified clouds observed by a LMA during HyMeX-SOP1 experiment
J.-P. Pinty(1), C. Bovalo(1), E. Defer(2), E. Richard(1),
P. Krehbiel(3), W. Rison(3), R. Thomas(3)
and NM Tech team & many HyMeX participants
(1) Lab. Aérologie, Toulouse,, France
(2) LERMA, Observatoire de Paris France
(3) New Mexico Tech., Socorro, USA
Motivations:
High-quality observations of the cloud electrical activity with a LMA(*) during the HyMeX SOP1 field experiment (Fall 2012)
Simulation of real cases to evaluate the explicit «electrical» module of MesoNH by comparison with LMA lightning data
(*) LMA: Lightning Mapping Array is manufactured by the New Mexico Tech., Socorro, NM
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

2. 9th HyMeX workshop, Mykonos, Greece, Sept, 2015
Outlines of the presentation
Short overview of the electrical scheme used to simulate real electrified clouds with MesoNH: focus on the links between cloud physics and cloud electricity
Simulations of meteorological «HyMeX» cases: Sept, 5th (isolated convection) and Sept, 26th, (moderate precip event) over the Cévennes area in the South of France and sensitivity experiments for the Sept, 24th case (IOP6).
Ref: Barthe et al., GMD, 2012; Pinty et al., AR, 2012; Defer et al., AMT, 2015
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

3. Electrical scheme of MesoNH
3 CRM (Mansell et al., 2002; Barthe et Pinty, 2007; Fierro et al., 2013) with a complete explicit 3D electrical scheme.
electrical charges electric field lightning flashes
||E||>Etrig
Numerical method
Coupling with cloud
μphysics (NI charging process TAKAH/SAUND)
and physics of the ions
Conceptual model
leaders & branches
 Partial charge
neutralization
(Eq. is solved for with
I and BC)
Continuous charging
(μphysics)
Discrete discharging
(flashes)
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

4. Electrical charging rate vs
Mass growth rate (1)
r: mixing ratio, q: electrical charge (bulk quantities)
Transfer terms, i.e. riming, melting  parametric model
Sedimentation  analytical integration
is provided by physics
where Vx is the fall speed
 Charge separation at cloud scale (at the origin of E)
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

5. Electrical charging rate vs
Mass growth (2)
 Charge separation at micro-scale (at the origin of qx)
Non-Inductive charging  physical model with 3 types of «ice-ice» interactions (ICE3 scheme)
where Kxy is the collision kernel
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

6. Electrical charging rate vs
Mass growth (2)
Jayaratne et al. (1983)
Takahashi (1978)
Saunders & Peck (1998)
Saunders et al. (1991)
 Charge separation at micro-scale (at the origin of qx)
Non-inductive charging  physical model with 3 types of «ice-ice» interactions (ICE3 scheme)
Look-up tables or
Expressions (LWC,T)
where Kxy is the collision kernel
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

7. Electrical charging rate vs
Mass growth (2)
Jayaratne et al. (1983)
Takahashi (1978)
Saunders & Peck (1998)
Saunders et al. (1991)
 Charge separation at micro-scale (at the origin of qx)
Non-inductive charging  physical model with 3 types of «ice-ice» interactions (ICE3 scheme)
Look-up tables or
Expressions (LWC,T)
where Kxy is the collision kernel
Exy: collection efficiency  r
1-Exy: rebounding efficiency  q
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

8. Electrical charging rate vs
Mass growth (2)
Jayaratne et al. (1983)
Takahashi (1978)
Saunders & Peck (1998)
Saunders et al. (1991)
 Charge separation at micro-scale (at the origin of qx)
Non-inductive charging  physical model with 3 types of «ice-ice» interactions (ICE3 scheme)
Look-up tables or
Expressions (LWC,T)
where Kxy is the collision kernel
Exy: collection efficiency  r
1-Exy: rebounding efficiency  q
NO Non-Inductive charging when hail is involved explicitly (4 types of ice particles: ICE4 scheme)
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

9. Known uncertainties when simulating
explicitly the electrical state of the clouds
CHARGING PHASE
Tuning of the parent microphysical scheme : 3-4 ice particle types and amount of supercooled water
Choice of the adequate charge separation diagram qxy as several diagrams are available from lab. experiments
DISCHARGING PROCESS
Choice of the fractal dimension to represent the spread of the flashes (in our electrical scheme CELLS)
Selection of IntraCloud vs Cloud-to-Ground flashes
 HyMeX LMA dataset to test the electrical scheme
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

10. The 05 Sept. 2012 Case Synoptic situation
(Low-level situation at 15 UTC, after 9 h run from _06UTC AROME analysis)
Grid-nested simulation: 192x192 4km and 384x384 1km
950 hPa equiv. Pot. Temp. and Wind
Radar (dBZ) at z=2000m
Massif
Central
(4 km horiz. resolution)
Alps
Reflectivity composite
Pyrenees
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

11. The 5 Sept. 2012 Case: 15:00-21:00 RADAR Observation
6 hour RESTART with ELEC scheme
15: : : : :00
RADAR
Grid-nested simulation: 192x192 4km and 384x384 1km
Observation
Simulation: 384x384
FLASHES
« Montpellier » storm
Spurious cells
LMA flashes (color) and EUCLID impacts (black)
IC cover (color) and CG impacts (black)
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

12. The 5 Sept. 2012 Case Close view of “Montpellier” storm
Data
Simulation
LMA & EUCLID data
IC density & IC trig. locations
Simulation:
+ accurate location and
duration of the storm
+ flash rate (SAUN2 & SAP98)
- lack of CG
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

13. The 5 Sept. 2012 Case Electrical charges : 05 Sept 17:45
+2nC/kg
Pristine ice
High & Low level flashes
-2nC/kg
+2nC/kg
Snow-Aggr.
 Tripole charge structure
-2nC/kg
Total charge & ||E||
Graupel
+2nC/kg
-2nC/kg
+2nC/kg
Rain
||E|| max ~ 100 kV/m
-2nC/kg
LMA & EUCLID data
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

14. The 5 Sept. 2012 Case Electrical state at ground level
Charge of the raindrops
+2nC/kg
-2nC/kg
Electric field: Ez
+10kV/m
+1kV/m
-1kV/m
-10kV/m
Ground Level
LMA & EUCLID data
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

15. The 26 Sept. 2012 Case Synoptic situation
(Low-level situation at 04 UTC, after 4 h run from _00UTC AROME analysis)
Grid-nested simulation: 192x192 4km and 384x384 1km
950 hPa equiv. Pot. Temp. and Wind
Radar (dBZ) at z=2000m
Alps
Massif
Central
(4 km horiz. resolution)
Precip rate (mm/h) at GL
Pyrenees
(4 km horiz. resolution)
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

16. The 26 Sept. 2012 Case Rainfall (log scale)
8 hours RESTART with ELEC scheme
{26 Sept 04:00}-{26 Sept 12:00}
Max=89 mm (Ardèche)
MesoNH: Max=76 mm
8 h grid-nested run with explicit «Electricity» module
Initial state = 4 h model run from :00UTC «Arome» analysis
4-km 3-h External Lateral forcing with «Arome» analyses (at 2.5 km)
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

17. The 26 Sept. 2012 Case ELEC results MesoNH: 00-04 then 04-12 with ELEC
Grid-nested simulations: 192x192 4km and 384x384 1km
05: : : : :30
LMA data 04-12
26 Sept CASE
MesoNH: then with ELEC
TAKAH: 5734 IC,
1093 CGN
SAUND: IC
396 CGP
SAP98 : IC
241 CGP
3030 fl.
EUCLID 2178 fl.
04: :00
TRIG. Loc.
04: :00
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

18. The 26 Sept. 2012 Case ELEC results MesoNH: 00-04 then 04-12 with ELEC
Grid-nested simulations: 192x192 4km and 384x384 1km
05: : : : :30
LMA data 04-12
26 Sept CASE
MesoNH: then with ELEC
TAKAH: 5734 IC,
1093 CGN
SAUND: IC
396 CGP
SAP98 : IC
241 CGP
Red color means CGP
3030 fl.
EUCLID 2178 fl.
04: :00
TRIG. Loc.
04: :00
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

19. The 24 Sept. 2012 Case a sensitivity study (6 hours)
ICE3 Precip
Reference simulation ICE3
Additional simulations: ICE4 : 4 categories of ice (hail) and flash fractal dimension 2.0<<2.5
Flash observation: 13,138 (LMA) and 20,917 (Euclid)
6h Precip
Number of flashes
Simulation
TAKAH
SAUND
SAP98
ICE3
13,748
ICE4
12,293
7,861
3,801
=2.0
20,122
=2.5
11,788
ICE4 Precip
 Less flashes when hail is considered explicitly and when the flash fractal dimension is increased
9th HyMeX workshop, Mykonos, Greece, Sept, 2015

20. 9th HyMeX workshop, Mykonos, Greece, Sept, 2015
Conclusion
The electrical module CELLS of the Cloud-Resolving Mesoscale Model MesoNH is able to simulate explicitly 3D electrified clouds on multiprocessor computers over complex terrain at km scale for several hours
The meteorological «HyMeX» simulations are encouraging for an evaluation of the scheme against LMA data (and other lightning detection networks). The accuracy of the convective cells location is a first limitation but simulations with Saunders et al., (1991) separation rate seem to perform the best
LMA data: total flash count, flash horizontal extension, polarity of the cloud layers, triggering & propagation altitudes, etc. are useful features to check in the model
Perspectives of the modeling work in cloud electricity: The electrical scheme was run intensively for many «HyMeX» cases encompassing the LMA network for data comparison  work to do:
to check carefully the 3D electrical state of the simulated clouds
to improve the IC/CG flash selection criteria for better results
9th HyMeX workshop, Mykonos, Greece, Sept, 2015