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Impact of lightning-NO emissions on eastern United States photochemistry during the summer of 2004 as determined using the CMAQ model. Dale Allen – University of Maryland, College Park, MD Ken Pickering – NASA GSFC, Greenbelt, MD Rob Pinder – US EPA, RTP, NC Tom Pierce – US EPA, RTP, NC

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slide1

Impact of lightning-NO emissions on eastern United States photochemistry during the summer of 2004 as determined using the CMAQ model

Dale Allen – University of Maryland, College Park, MD

Ken Pickering – NASA GSFC, Greenbelt, MD

Rob Pinder – US EPA, RTP, NC

Tom Pierce – US EPA, RTP, NC

2009 CMAS Meeting

October 19-21, 2009

motivation for including lightning no x in cmaq
Motivation for Including Lightning NOx in CMAQ
  • In the summer over the US, production of NO by lightning (LNOx) is responsible for 60-80% of upper tropospheric (UT) NOx and 20-30% of UT ozone.
  • Mid- and upper-tropospheric ozone production rates are highly sensitive to NOx mixing ratios.
  • Inversion-based estimates of NO emissions from CMAQ simulations without lightning-NO emissions have large errors at rural locations.
  • CMAQ-calculated nitrogen deposition is much too low when lightning-NO emissions are not included (e.g., Low-bias in CMAQ-calc nitric acid wet dep at NADP sites cut in half when lightning-NO was added).
  • Lightning-NO emissions can add several ppbv on average to summertime surface ozone concentrations
outline
Outline
  • Describe method used to parameterize lightning-NO emissions within CMAQ.
  • Use CMAQ with and without lightning-NO emissions to simulate the tropospheric distribution of atmospheric trace gases over the US during the summer of 2004
  • Compare CMAQ-calculated trace gas distributions with

NOx and ozone measurements from INTEX-A field campaign

tropospheric NO2 columns from SCIAMACHY

  • Estimate the contribution of lightning-NO emissions to 8-hour maximum ozone
cmaq setup
CMAQ setup
  • Continental US 36-km domain with 24 vertical layers from the surface to 100 hPa.
  • Meteorological fields from MM5
  • Emissions from SMOKE processing of 2002 NEI for use with CB-05 chemical mechanism
  • Year-appropriate point source emissions from CEMS
  • Mobile emissions processed by Mobile6
  • Meteorologically adjusted biogenic emissions from BEIS 3.13
cmaq lightning no emission parameterization
CMAQ Lightning-NO emission Parameterization

LNOx = k* PROD*LF, where

k: Conversion factor (Molecular weight of N / Avogadros #)

PROD: Moles of NO produced per flash

LF: Total flash rate (IC + CG), where

LF = G * αi,j * (preconi,j – threshold), where

Precon: Convective precipitation rate from MM5

threshold: Value of precon below which the flash rate is set to zero.

G: Scaling factor chosen so that domain-avg MM5 flash rate matches domain averaged observed flash rate.

αi,j: Local scaling factor chosen so that monthly avg model- calc flash rate for each grid box equals local observed flash rate

For these retrospective simulations, the observed flash rate is the NLDN-based total flash rate for June, July, and August 2004.

Operational forecasts could use satellite-retrieved or NLDN-based climatological flash rates for a season as observations.

what is the nldn based total flash rate
What is the NLDN-based total flash rate?
  • Hourly cloud-to-ground flash rates (CG) from the National Lightning Detection Network (US only) are mapped onto the CMAQ grid.
  • Hourly total flash rates (CG +IC) are estimated by multiplying the CG flash rate by (Z+1), where Z is the climatological IC/CG ratio Boccippio et al. [2001] determined by comparing satellite-retrieved (Optical Transient Detector instrument) total flash rates with NLDN CG flash rates.
  • Cautionary note:
  • Errors in NLDN-based total flash rate can be substantial as 1) IC flashes > CG flashes , 2) 1995-1999 data set, 3) OTD only samples a few percent of total flashes
slide7

Boccippio et al., 2001

Mean IC/CG ~3. Adds uncertainty to NLDN-based total flash rate

slide8

Impact of local scaling on CMAQ-calculated flash rate

CMAQ-

Based

CG+IC

(without

α)

NLDN

Based

CG+IC

flash

rate

Local scaling compensates

for regional biases in

convective precipitation and

for continental-marine

differences in the relationship

between flash rate and precip

CMAQ

Based

CG+IC

(With

α)

slide9

Day-to-day and diel fluctuations in flash rate over the

Eastern US (110°-70°W, 25°-45° N)

August 1 to August 31, 2004

slide11

Day-to-day fluctuations in flash rate

(110°-70°W, 25°-45° N) well captured

August 1 to August 31, 2004

lno x production per flash
LNOx Production Per Flash
  • Globally, lightning produces 2-8 Tg N / year with a 5 Tg N / year source corresponding to a mean source of ~250 moles of N / flash.
  • However, recent cloud resolved chemistry modeling (DeCaria et al., 2000; 2005; Ott et al., 2005; 2007) of observed convective events (STERAO, EULINOX, CRYSTAL-FACE) and recent modeling of the INTEX-A period using GEOS-Chem, FLEXPART, REAM and other models [Singh et al., 2007] indicates that midlatitude and subtropical lightning has a mean source of ~500 moles of N / Flash.
  • In these simulations both IC and CG flashes are assumed to produce 500 moles of N.
  • Note: Lightning-NO production is proportional to flash channel length. W. Koshak of NASA-MSFC is calculating frequency distributions of flash channel lengths from the Lightning Mapping Array (LMA). In future simulations, we hope to use flash channel length PDFs to add variability to the lightning-NO produced per flash.
slide24

Vertical Distribution of VHF

Sources – Northern Alabama

Lightning Mapping Array

Apr.-Sept. 2003-2005

Vertical distribution of

VHF sources from

Alabama LMA

is used along with a

direct relationship with

pressure to determine

the fraction of

emissions to put into

each layer from the

surface to the CMAQ-

predicted cloud top

When available, vertical

distributions of flash

channel length from the

LMA may provide more

accurate vertical

distribution information

Vertical

Distribution of

LNOx

Emissions

Used in CMAQ

D. Buechler, NASA/MSFC

slide25

Comparison of CMAQ-calc NOx with INTEX-A measurements

NOx DC-8 Flight 12 July 25, 2004

CMAQ

Without

Lightning

NO

CMAQ

With

Lightning

NO

slide26

Comparison of CMAQ-calc ozone with INTEX-A observations

CMAQ

Without

lightning

CMAQ

With

lightning

slide28

Comparison with INTEX-A ozone measurements

Low-bias in UT CMAQ-calc ozone also due to lack of

Stratospheric ozone and aircraft NOx emissions

slide29

CMAQ

No

Lightning

SCIA

10:00 AM LT CMAQ output used

Tropp = 150 hPa

No averaging kernel applied

CMAQ

With

Lightning

slide30

Bias in

No Lightning

Run

Bias in

Run with

lightning

summary
Summary
  • Lightning-NO emission algorithm was added to CMAQ
  • Lightning-NO algorithm captures diel and day-to-day fluctuations in lightning flash rate
  • Addition of lightning-NO to CMAQ reduces low-bias between CMAQ-calc and measured NOx in UT. However, substantial low-bias still remains. Low-bias could be due to remaining errors in the source per flash but could also indicate that the NOx lifetime in the UT is too short in CMAQ and in other models.
  • Addition of lightning-NO reduces low-bias wrt SCIAMACHY in CMAQ-calculated tropospheric NO2 column from 22% to 5%.
  • Lightning-NO emissions in CMAQ contribute less than 2 ppbv of ozone to 8-hour maximum ozone on 75% of high ozone days
future work
Future Work
  • Lightning-NO algorithm suitable for operational forecasts will be developed and tested (constrain using climatological flash rates)
  • Simulations with variable lightning-NO production per flash will be run (channel length PDFs of Koshak)
  • Simulations with more realistic vertical distribution of lightning-NO flashes will be run (addition of vertical layers in CMAQ; incorporation of vertical distribution of flash channel length information from Koshak)
  • Simulations including aircraft NO emissions will be run
  • Simulations of additional periods including 2006
  • Output from simulations will be used in inverse studies to constrain NO emissions and in nitrogen deposition investigations
  • Test WRF-Chem LNOx scheme of A. Hansen (FSU) – more microphysically based
  • Note: Support for this project provided by NASA’s Applied Sciences Air Quality Decision Support System Program.
missing no 2 aloft
When paired with aloft measurements from NASA INTEX, CMAQ underpredicts NO2 above the mixed layer

Consistent on all flights during the summer of 2004

On average 1.07 (1015 molecules cm-2)

Missing NO2 Aloft

Pinder et al., 2008

slide37

Lightning NO Production Scenarios

Summary of Five Midlatitude and Subtropical Storms

Orville et al., 2002

Means: 500 moles/flash

0.93 ratio

For global rate of 44

flashes/sec, this implies

~9 Tg N/yr

slide46

Note: CMAQ does not include a stratospheric source of ozone.

Upper tropospheric low-biases are expected.

slide49

Comparison with IONS ozonesondes over Houston, TX

Blue (No Lightning); Red (with Lightning), Black (IONS)