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Toward a new parameterization of nitrogen oxides produced by lightning flashes

Toward a new parameterization of nitrogen oxides produced by lightning flashes in the WRF-AqChem model. Christelle Barthe NCAR/ACD Previously at Laboratoire d’Aerologie, Toulouse, France. ASP Research Review. March 1, 2007. Why to model the lightning flashes ?.

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Toward a new parameterization of nitrogen oxides produced by lightning flashes

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  1. Toward a new parameterization of nitrogen oxides produced by lightning flashes in the WRF-AqChem model Christelle Barthe NCAR/ACD Previously at Laboratoire d’Aerologie, Toulouse, France ASP Research Review March 1, 2007

  2. Why to model the lightning flashes ? • To better understand the cloud electrical processes… • Forecasting severe storms (hail, lightning flashes, precipitations) • - Lightning flashes can be easily observed •  tracers of physical parameters • ice water content [Petersen et al., 2005] or ice flux [Deierling, 2006] • precipitation rate [Baker et al., 1995; Soula and Chauzy, 2001] • NOx production by lightning flashes [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 [Fierro et al., in press] … ASP Research Review March 1, 2007

  3. Outline • 1 – Overview of the electrical scheme in Meso-NH • cloud electrification • lightning flashes • 2 – Lightning-produced NOx in cloud resolving models • the July 10 STERAO storm simulated with Meso-NH • models intercomparison • future LiNOx parameterization for WRF ASP Research Review March 1, 2007

  4. + graupel - TCR - + ice crystal How clouds become electrified … at the local scale Electric charges carried by hydrometeors (initially neutral) Non-inductive charging process  Elastic collisions between more or less rimed particles • The separated charge depends on: • temperature • supercooled water content TCR = Temperature Charge Reversal Inductive charging process  Elastic collisions between cloud droplets and graupel in presence of E ASP Research Review March 1, 2007

  5. How clouds become electrified … at the cloud scale • charge transfer between particles during microphysical processes Pinty and Jabouille [1998] • charge transport at the cloud scale (gravity and convection) ASP Research Review March 1, 2007

  6. + + - - + + Different electrical cloud structures Stolzenburg et al. [1998] - - Williams [1988] + + - - + + - + ASP Research Review March 1, 2007

  7. Lightning flash structure In Meso-NH: • a flash is triggered when the electric field exceeds a threshold thatdepends on the altitude [Marshall et al., 1995] • Vertical extension of the flash Bidirectional leader Segments propagate in the directions // and anti// to the electric field • Horizontal extension of the flash Branching algorithm  dielectric breakdown model Fractal law to describe the number of branches Barthe and Pinty [2007] ASP Research Review March 1, 2007

  8. Lightning flash structure In Meso-NH: • a flash is triggered when the electric field exceeds a threshold thatdepends on the altitude [Marshall et al., 1995] • Vertical extension of the flash Bidirectional leader Segments propagate in the directions // and anti// to the electric field • Horizontal extension of the flash Branching algorithm  dielectric breakdown model Fractal law to describe the number of branches Barthe and Pinty [2007] http://www.lightning.nmt.edu/nmt_lms/ ASP Research Review March 1, 2007

  9. Lightning flash structure In Meso-NH: • a flash is triggered when the electric field exceeds a threshold thatdepends on the altitude [Marshall et al., 1995] • Vertical extension of the flash Bidirectional leader Segments propagate in the directions // and anti// to the electric field • Horizontal extension of the flash Branching algorithm  dielectric breakdown model Fractal law to describe the number of branches Barthe and Pinty [2007] http://www.lightning.nmt.edu/nmt_lms/ ASP Research Review March 1, 2007

  10. Lightning flash structure Volume of charge neutralized by an individual flash Barthe and Pinty [2007] Electric charges are neutralized along the flash channel leading to a decrease of the electric field Rison et al. [1999] ASP Research Review March 1, 2007

  11. 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. [2005] http://mesonh.aero.obs-mip.fr/mesonh/ ASP Research Review March 1, 2007

  12. Lightning-produced NOx (LiNOx) Lee et al. [1997] Lightning = major natural source of NOx but with large uncertainties LiNOx  impact on ozone, oxidizing power of the troposphere… Hauglustaine et al. [2001] ASP Research Review March 1, 2007

  13. LiNOx production in the 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] ASP Research Review March 1, 2007

  14. 0102 UTC 2202 UTC Lightning-produced NOx Meso-NH : 2048 flashes Defer et al. [2001] : 5428 flashes with 50% short duration flashes (< 1 km) ASP Research Review March 1, 2007

  15. Lightning-produced NOx 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) ASP Research Review March 1, 2007

  16. Lightning-produced NOx Intercomparison exercise STERAO: July 10, 1996 Barth et al., in preparation ASP Research Review March 1, 2007

  17. Lightning-produced NOx • Parameterized LiNOx [Pickering et al., 1998] • (WRF, GCE, Wang, RAMS) • overestimation of the LiNOx production in the lower part of the cloud • can’t represent the peaks of fresh NO • volumic distribution of NO Explicit LiNOx / lightning scheme (SDSMT, Meso-NH) • LiNOx are produced between 7 and 13 km • distribution of NO along the flash path  important for transport and chemistry ASP Research Review March 1, 2007

  18. LiNOx parameterization in CRM (WRF) • Cell identification • Identification of the updrafts (wmax > 10-15 m s-1  electrification) • horizontal extension of the cell – based on microphysics • Temporal evolution of the flash frequency • Strong correlation between flash frequency and microphysics at the cloud scale (Blyth et al., 2001; Deierling, 2006) • Flash length •  ~ 20-50 km but high variability from observations (Defer et al., 2003; Dotzek et al., 2000…) and modeling studies (Pinty and Barthe, 2007) • Spatial distribution of the NO molecules •  bilevel distribution of IC flashes (MacGorman and Rust, 1998; Shao and Krehbiel, 1996; Krehbiel et al, 2000; Thomas et al, 2000, 2001) •  random choice of the segments to mimic the tortuous and filamentary aspect of the flashes where presence of both ice crystals and graupel • Amount of NO produced per flash •  proportional to the flash length and depends on the pressure ASP Research Review March 1, 2007

  19. LiNOx parameterization in CRM – flash rate Deierling (2006) Linear relationship between ice mass flux and flash frequency: f = 2.47 10-15 (Fip) + 14.14 (r = 0.96) July 10, 1996 STERAO storm ASP Research Review March 1, 2007

  20. LiNOx parameterization in CRM – flash rate Simulation of the July 10 STERAO storm - WRFV2 - Microphysical scheme : Lin et al. (1983) ASP Research Review March 1, 2007

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