Electricité atmosphérique etProduction d’oxydes d’azote par les éclairs:

Etat des lieux et perspectives

Christelle Barthe1 et Jean-Pierre Pinty

Laboratoire d’Aérologie1Now at National Center for Atmospheric Research

4th Meso-NH user’s Meeting April 23-24, 2007

4th Meso-NH user’s Meeting April 23-24, 2007

ice water content [Petersen et al., 2005] ice flux [Deierling, 2006] precipitation rate [Baker et al., 1995; Soula and Chauzy, 2001] NOx production [Lee et al, 1997; Huntrieser et al., 1998] water vapor in the upper troposphere [Price, 2000] climate change index [Reeve and Toumi, 1999] tropical cyclones intensification [Molinari et al., 1994; Fierro et al., 2007] …

- A better understanding of a cloud natural process …

- An index of storm severity : hail, heavy precipitations, gust winds and … lightning flashes

- Lightning flashes are routinely detected tracers of physical parameters ?

Why to model the lightning flashes ?

4th Meso-NH user’s Meeting April 23-24, 2007

Meso-NH-elec : flow chart

Charges separation

Charges transfer and transport

Electric field computation

Bidirectional leader

Branches

Charge neutralization

NOx production

E > Etrig

E > Eprop

Dynamical and microphysical processes

yes

no

no

yes

Barthe et al. [2005]

Vertical extension of the flash

Horizontal extension of the flash

4th Meso-NH user’s Meeting April 23-24, 2007

Lightning flashes structure

Volume of charge neutralized by an individual flash

Barthe and Pinty [2007]

Rison et al. [1999]

Electric charges are neutralized along the flash channel leading to a decrease of the electric field

4th Meso-NH user’s Meeting April 23-24, 2007

Lightning-produced NOx – July 10, 1996 STERAO storm

Physical packages• transport : MPDATA• microphysics : ICE3 [Pinty et Jabouille, 1998]• electrical scheme [Barthe et al., 2005]• gas scavenging [C. Mari]• LiNOx [Barthe et al., 2007] flash length and depends on the altitude nNO(P) = a + b x P (1021 molecules m-1) [Wang et al., 1998]• turbulence 3D : TKE [Cuxart et al., 2000]

Initialization• 10 July STERAO storm• 160 x 160 x 50 gridpoints with x = y = 1 km and z variable• initial sounding + 3 warm bubbles [Skamarock et al., 2000]• chemical species profiles (HCHO, H2O2, HNO3, O3, CO and NOx) [Barth et al., 2001]

4th Meso-NH user’s Meeting April 23-24, 2007

July 10, 1996 STERAO storm: transition from multicell to supercell

2202 UTC 0102 UTC

Meso-NH : 2048 flashes

Defer et al. [2001] : 5428 flashes with 50% short duration flashes (< 1 km)

4th Meso-NH user’s Meeting April 23-24, 2007

July 10, 1996 STERAO storm: LNOx production

NO concentrations measured by the Citation at 11.6 km msl from 2305 to 2311 UTC, 10 - 15 km downwind of the core [Dye et al., 2000]

transport of NOx from the boundary layer to the upper troposphere (~ 200 pptv)

LNOx production between 7500 and 13,500 m (peak value ~ 6000 pptv) and dilution (~ 1000 pptv)

Vertical cross section of the NOx concentration and the total electric charge density (±0.1, ±0.3 and ± 0.5 nC m-3) in the multicellular stage

Barthe et al. [2007]

4th Meso-NH user’s Meeting April 23-24, 2007

July 10, 1996 STERAO storm: intercomparison exercise

Intercomparison exerciseSTERAO: July 10, 1996Barth et al., to be submitted to ACPD

4th Meso-NH user’s Meeting April 23-24, 2007

Conclusions

Full electric charge cycle in a mesoscale model • charges separation, transfer, transport and neutralization

Lightning flash treatment• original branching scheme with wide horizontal extension• good neutralization efficiency of the flash scheme

Explicit formation of lightning-produced NOx

• great potential for gaseous chemistry

Simulations in different idealized convective conditions • squall line, supercell, multicell storms in 2D and 3D

Cloud electrification• crucial to reproduce the cloud polarity• high sensitivity to the treatment of the NI processes [Barthe and Pinty, J. Geophys. Res., in revision]• part of the code is implemented in the UK MetOffice LEM

Ensemble simulations of electrified clouds• [Pinty and Barthe, submitted to Month. Wea. Rev.]

4th Meso-NH user’s Meeting April 23-24, 2007

Perspectives

Parallelization efficiency of the lightning algorithm Integration of the full electrical scheme in the next (4.8) version of Meso-NH ? (***)

Explicit treatment of the ions (**)

Sensitivity to surface properties for coronae effects (*)

Real case simulations: MAP, TELEX, STEPS, AMMA, Mediterranean storms, COPS … (***)

LNOx impact on some chemical species: HNO3, O3… (***)