Lightning NO Productionin the GMI Model

Kenneth E. Pickering

Dale J. Allen

Department of Meteorology

University of Maryland

College Park, MD

Outline

• Current procedure in GMI model• Necessity of co-locating lightning NO with

convective transport• Available parameterizations• What can be done in the GMI model?

Current Procedure• Climatological monthly spatial distributions of total

(CG+IC) lightning flashes (Price et al., 1997) based on ISCCP deep convective cloud top heights (Price and Rind, 1992).

• CG fraction based on cold cloud depth (Price and Rind, 1993)

• PCG = 10 PIC ; PCG= 6.7 x 1026 molec/flash (Price et al., 1997)

• Grid cell NO production values scaled such that global production equals a specified value (e.g., 5 TgN/yr)

• Vertically distributed according to C-shape profiles derived from cloud-resolving model simulations of Pickering et al. (1998)

Lightning NO and Convective Transport

• Use of climatological lightning NO production results in lightning NO not being injected into the model at same times and locations as at which the model convective transport occurs

• Therefore, lightning NO and convectively-transported species (HOx precursors, NO, CO, NMHC) are introduced to the upper troposphere in different locations

• Results in “fuzzy” middle and upper tropospheric chemistry

• Lightning and convection need to be co-located!

Lightning and Convection

• Therefore, it is not advisable to use climatological lightning based on ISCCP or based on OTD/LIS observations

• Also, should not try to use OTD/LIS daily data (in addition to same location problem, daily data is a tiny, very unrepresentative sample of actual lightning

• LIGHTNING FLASH RATES MUST BE PARAMETERIZED IN TERMS OF VARIABLES FROM THE MODEL CONVECTIVE SCHEME

Available Parameterizations

• Cloud-height-based approach

Price and Rind (1992)• Cloud-mass flux based approach

Allen and Pickering (2002) • Convective precipitation based approach

Allen and Pickering (2002)

All using fields from driving GCM/DAS

IC/CG ratios calculated using cold cloud depths as before

Available Parameterizations

• IC/CG ratio from cold-cloud depth method vs. from OTD/NLDN measurements

• NO production per flash: PCG = 10 PIC ???- NO spikes observed from aircraft (mostly associated with IC flashes) show 2 orders of magnitude variability in terms of molecules NO per meter of flash length

- STERAO-A results (DeCaria et al, 2000) show average NO production per IC flash nearly equal to that per CG flash

Author Production (molecules NO per m flash length)

Field Project

Stith et al. [1999] 2 x 1020 – 1.0 x 1022 STERAO

Skamarock et al. [2002] 1.0 x 1021 STERAO

Höller et al. [1999] 1 – 4 x 1022 LINOX

Huntrieser et al. [2002] 2.7 x 1021 EULINOX

Analyses of Observed NO Spikes

For the midpoint of this range (3 x 1021) and a 30-km flash length ~1 x 1026 molecules NO/flash

CG: 460IC:46

CG: 460

IC: 460

CG: 460 IC: 345

CG: 460

IC: 690

Moles NOPer Flash

Model-simulated vs. Measured NOx ProfilesFor Four Lightning NO Production Scenarios

DeCaria et al. (2000)460 moles NO/flash ~3 x 10 26 molecules NO/flash

STERAO-A July 12, 1996 NE Colorado

What can be done in the GMI model?

• Run a flash rate parameterization for the year of interest, producing IC and CG flash rates for every meteorological data interval (e.g., 6 hours)

• Calculate NO production for each grid cell for each meteorological data interval

• Compute total global annual production• Scale time series of gridded production values to

some reasonable desired global annual production• Input the scaled time series to the CTM

Which flash rate parameterizationshould be used?

• Cloud-top height method does not yield realistic variability in flash rates when implemented with GEOS-DAS data

• Cloud mass flux method underpredicts flash rates in Africa and overpredicts flash rates in Western Pacific when used with GEOS/STRAT data

- GEOS-3 cloud mass fluxes smaller than in GEOS-STRAT

- GEOS-3 TRMM assimilation of precipitation over oceans (1998 – present)

- Rondonia Brazil lightning network (’99-’01)

GEOS-3 Control and GEOS-3 TRMM vs. OTD

Lightning Activity - Daily Detections(31 day moving average)

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

J F M A M J J A S O N D

Month

Sit

e D

ete

cti

on

s (

~s

tro

ke

s)

1999 2000 2001

Apply cloud-top height and cloud mass flux parameterizations with:

• GEOS-3/TRMM -DAS• GEOS-4 DAS • GISS• CCM3• Others?

Perform sensitivity runs in the GMI model and make a decision on the formulation to be used

Time Line1) Nov. 03 – Jan. 04: Work with GEOS-3

TRMM DAS and Brazil observed lightning at U. of MD to improve parameterizations in tropics

2) Feb 04 – Mar. 04: Compute lightning NO source using CLDHT and MFLUX parameterizations for each set of met. fields and perform sensitivity testing (collaboration of U. of MD and GMI Core Team)

3) Apr. 04 – June 04: Work on paper(s) concerning changes in model chemistry resulting from change to co-located lightning and convection (Chatfield, Pickering, Allen, others)