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
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 ?
ASP Research Review March 1, 2007
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
How clouds become electrified … at the local scale
graupel
ice crystal
TCR
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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
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Williams [1988]
Stolzenburg et al. [1998]
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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 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]
ASP Research Review March 1, 2007
Lightning flash structure
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
Barthe and Pinty [2007]
ASP Research Review March 1, 2007
Lightning flash structure
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
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
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/
ASP Research Review March 1, 2007
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…
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 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]
ASP Research Review March 1, 2007
Lightning-produced NOx
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 NOx
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
ASP Research Review March 1, 2007
Lightning-produced NOx
Intercomparison exerciseSTERAO: July 10, 1996Barth et al., in preparation
ASP Research Review March 1, 2007
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
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
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