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/ACDPreviously at Laboratoire d’Aerologie, Toulouse, France

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]

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] …

-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 ?


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


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


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)


Different electrical cloud structures

+

+-

+

+-

Williams [1988]

Stolzenburg et al. [1998]

+-

-++-

-+

+

-


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 flashBidirectional leaderSegments propagate in the directions // and anti// to the electric field

Horizontal extension of the flashBranching algorithm dielectric breakdown modelFractal law to describe the number of branches

Barthe and Pinty [2007]



http://www.lightning.nmt.edu/nmt_lms/

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 flashBidirectional leaderSegments propagate in the directions // and anti// to the electric field

Horizontal extension of the flashBranching algorithm dielectric breakdown modelFractal law to describe the number of branches




Volume of charge neutralized by an individual flash


Rison et al. [1999]

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


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]

MESO-NH-ELEC – flow chart

Vertical extension of the flash

Horizontal extension of the flash

http://mesonh.aero.obs-mip.fr/mesonh/


Lightning-produced NOx (LiNOx)

Lee et al. [1997]

Hauglustaine et al. [2001]

Lightning = major natural source of NOx but with large uncertainties

LiNOx impact on ozone, oxidizing power of the troposphere…


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 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]


Lightning-produced NOx

2202 UTC 0102 UTC

Meso-NH : 2048 flashes

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



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



Intercomparison exerciseSTERAO: July 10, 1996Barth et al., in preparation



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


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


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


LiNOx parameterization in CRM – flash rate

Simulation of the July 10 STERAO storm- WRFV2 - Microphysical scheme : Lin et al. (1983)

toward a new parameterization of nitrogen oxides produced by lightning flashes

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