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Electricité atmosphérique et Production d’oxydes d’azote par les éclairs: Etat des lieux et perspectives Christelle Barthe1 et Jean-Pierre Pinty Laboratoire d’Aérologie 1Now at National Center for Atmospheric Research 4th Meso-NH user’s Meeting April 23-24, 2007
Why to model the lightning flashes ? - 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 ? • 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] … 4th Meso-NH user’s Meeting April 23-24, 2007
Meso-NH-elec : flow chart Charges separation Dynamical and microphysical processes Charges transfer and transport Electric field computation no E > Etrig NOx production yes Bidirectional leader Vertical extension of the flash yes E > Eprop no Branches Horizontal extension of the flash Charge neutralization Barthe et al.  4th Meso-NH user’s Meeting April 23-24, 2007
Lightning flashes structure Volume of charge neutralized by an individual flash Barthe and Pinty  Electric charges are neutralized along the flash channel leading to a decrease of the electric field Rison et al.  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] a 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 Dx = Dy = 1 km and Dz 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
0102 UTC 2202 UTC July 10, 1996 STERAO storm: transition from multicell to supercell Meso-NH : 2048 flashes Defer et al.  : 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 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 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) Barthe et al.  4th Meso-NH user’s Meeting April 23-24, 2007
July 10, 1996 STERAO storm: intercomparison exercise Intercomparison exercise STERAO: July 10, 1996 Barth 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… (***) 4th Meso-NH user’s Meeting April 23-24, 2007