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 ReviewMarch 1, 2007

ASP Research Review March 1, 2007 ice water content [Petersen et al., 2005] or ice flux [Deierling, 2006] precipitation rate [Baker et al., 1995; Soula and Chauzy, 2001] NO x 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] … -To better understand the cloud electrical processes… - Forecasting severe storms (hail, lightning flashes, precipitations) - Lightning flashes can be easily observed  tracers of physical parameters Why to model the lightning flashes ?

ASP Research Review March 1, 2007 Outline 1 – Overview of the electrical scheme in Meso-NH cloud electrification lightning flashes 2 – Lightning-produced NO x 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 How clouds become electrified … at the local scale graupel ice crystal TCR 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 Electric charges carried by hydrometeors (initially neutral) Inductive charging process  Elastic collisions between cloud droplets and graupel in presence of E

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

ASP Research Review March 1, 2007 Lightning flash structure In Meso-NH:  a flash is triggered when the electric field exceeds a threshold that depends 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 Lightning flash structure In Meso-NH:  a flash is triggered when the electric field exceeds a threshold that depends 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 Lightning flash structure In Meso-NH:  a flash is triggered when the electric field exceeds a threshold that depends 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 Lightning flash 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

ASP Research Review March 1, 2007 Charges separation Charges transfer and transport Electric field computation Bidirectional leader Branches Charge neutralization NO x production E > E trig E > E prop Dynamical and microphysical processes yes no yes Barthe et al. [2005] MESO-NH-ELEC – flow chart Vertical extension of the flash Horizontal extension of the flash

ASP Research Review March 1, 2007 Lightning-produced NO x (LiNOx) Lee et al. [1997] Hauglustaine et al. [2001] Lightning = major natural source of NO x but with large uncertainties LiNOx  impact on ozone, oxidizing power of the troposphere…

ASP Research Review March 1, 2007 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]  flash length and depends on the altitude  n NO (P) = a + b x P (10 21 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, H 2 O 2, HNO 3, O 3, CO and NO x ) [ Barth et al., 2001]

ASP Research Review March 1, 2007 Lightning-produced NO x 2202 UTC 0102 UTC Meso-NH : 2048 flashes Defer et al. [2001] : 5428 flashes with 50% short duration flashes (< 1 km)

ASP Research Review March 1, 2007 Lightning-produced NO x NO concentrations measured by the Citation at 11.6 km msl from 2305 to 2311 UTC, km downwind of the core [Dye et al., 2000]  transport of NO x 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 NO x concentration and the total electric charge density (±0.1, ±0.3 and ± 0.5 nC m -3 ) in the multicellular stage

ASP Research Review March 1, 2007 Lightning-produced NO x Intercomparison exercise STERAO: July 10, 1996 Barth et al., in preparation

ASP Research Review March 1, 2007 Lightning-produced NO x 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 LiNOx parameterization in CRM (WRF) Cell identification  Identification of the updrafts (w max > 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  ~ 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 LiNOx parameterization in CRM – flash rate Deierling (2006) Linear relationship between ice mass flux and flash frequency: f = (F i p) (r = 0.96) July 10, 1996 STERAO storm

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