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North American Pollutant Export due to Anthropogenic Emissions and Lightning

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North American Pollutant Export due to Anthropogenic Emissions and Lightning. M a t u s M a r t i n i. Dale Allen, Ken Pickering, Georgiy Stenchikov, Ed Hyer Student Seminar November 12, 2008. What am I going to talk about?. Motivation for our study: radiative forcing

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North American Pollutant Export due to Anthropogenic Emissions and Lightning

Matus M artini

Dale Allen, Ken Pickering, Georgiy Stenchikov, Ed Hyer

Student Seminar

November 12, 2008

what am i going to talk about
What am I going to talk about?
  • Motivation for our study: radiative forcing
  • Air quality and long-range transport
  • Impact of anthro emissions, and lightning
  • Challenges to calculate the upper tropospheric NOx so important for long-range transport

Our calculation: UMDCTM, Ming-Dah Chou’s RTM

Radiative Forcing due to O3 resulted from anthropogenic emissions 2002

Tropospheric ozone

is the third most important

greenhouse gas.


Our calculation: UMDCTM, Ming-Dah Chou’s RTM

Radiative Forcing due to O3 resulted from anthropogenic emissions 2004

For comparison, IPCC 2007:

“Global present-day RF

due to tropospheric ozone

is 0.35 Wm-2.”

what is new in this study
What is new in this study?
  • What is the impact of NOx emissions (from power plants and lightning) on tropospheric ozone and the associated radiative forcing as a convenient measure of pollutant long-range export?
  • Are meteorology effects (lightning, convection) more influential than emission effects to long-range export? Important in changing climate.
  • Testing new lightning parameterization scheme with constraints to observations: space-based OTD/LIS, ground-based lightning detection network: NLDN
  • We would like to avoid using the lightning climatology – LNOx not being injected into the model at the same times and locations as where model convection occurs
  • This study is not complete.
  • NOx (NO + NO2) major O3 precursors <- fossil fuel combustion, lightning, soils, biomass burn, aircraft

Anthropogenic NOx sources

  • NOx SIP Call: NOx emissions reduced by 50% (Frost et al. 2006)
  • EPA issued Clean Air Interstate Rule March 2005 - 60% 2003/2015 reductions - reduce the impact on surface AQ (Kim et al. 2006)
  • Emission Database for Global Atmospheric Research (EDGAR):U.S. power generation accounted for one quarter (4.8 Tg NO2) of national NOx emissions (19.4 Tg NO2) which are dominated by mobile sources (road transport 6.3 Tg, international shipping 1.9 Tg and air transport 0.9 Tg of NO2).

In our study we use: state of the art CEMS (Continuous Emission Monitoring) monthly emission inventory (very accurate) over the US for NOx power plants

  • Lightning NOx
  • Abundance of water vapor and surface heating
  • Warmer climate may lead to increases in lightning activity
  • Simulating lightning NOx with satellite and in-situ obs is difficult:

esp. spatial distribution of flashes (Allen, Pickering 2002).

  • We use new LP (based on upward cloud mass flux) with constraints to obs
  • Models used
  • The UMD chemistry transport model - tropospheric chemical mechanism (Park et al. 2004) and is driven by fields from the GEOS-4 DAS.

- We use event-specific biomass burning emissions (Kasischke et al.2005, van der Werf et al. 2006)

  • Radiative transfer model (Chou et al. 1995)
meteorological effects temperature and moisture parameters
Meteorological Effects(temperature and moisture parameters)

In Godowitch et al. (2007),

meteorology has greater impact

than emission changes

on Air Quality

over the north part of

Ohio River Valley!

(20-80 % NOx reduction)

(3-5°C colder temp)

  • N American anthropogenic emissions contributed ~40 ppbV to 8-hr max O3 in UMD-CTM during 2004. Data show improved AQ between 2002 and 2004.
  • Emission reductions and a cooler, wetter summer contributed to lower 8-hr max. O3 in 2004 than 2002
  • Upper troposphere has much stronger lightning signal than the surface
  • Main lightning regions are North of Gulf of Mexico, AZ, AL, etc. not Ohio River Valley
  • Lightning NOx signal from SCIAMACHY is weak, comparable to the measurement uncertainty for tropospheric NO2 (0.5e15 molec NO2 cm-2)
  • Large uncertainty for cloudy scenes – little consequence, since long upper tropospheric NOx lifetime 5-10 days (clouds <-> lightning)
  • Higher measurement sensitivity to NO2 in the lower troposphere
  • Definition of tropopause
  • Major challenge in interpreting satellite obs of tropospheric column is ambiguity in the altitude of gas, dependent on a priori NO2 profile (from a model)
  • More accurate retrieval is needed: Martin et al. 2007
air quality long range transport
Air Quality -> Long-range transport
  • Surface O3 – air quality – importance of anthropogenic emissions
  • Upper troposphere O3 – climate forcing – importance of lightning
  • In 2004 better air quality (at the sfc)!
  • In spite of NOx reductions and colder sfc temperatures, radiative forcing due to tropospheric ozone was greater in summer 2004 than in 2002!
  • Tropo O3 is a GHG. UT has much stronger influence on sfc radiative fluxes (than polluted boundary layer).

Total flashrate

IC (intracloud) + CG (cloud to ground)

National Lightning Detection Network (NLDN) observes Cloud-to-Ground (CG) flashes which are then multiplied by climatological IC:CG (Z) ratio

Day of year


Total flash rate

IC (intracloud) + CG (cloud to ground)


Summer US lightning flashrate is

one half of

what’s over the global flashrate:

44 flashes / second

Day of year


Adjusted IC:CG ratios for June

IC:CG ratios for June, Boccippio et al. 2001

Our adjustment:

1.exclude offshore high-values

2. smooth some more

3. interpolate


1. dependence on altitude


2. high anomaly CO

3.CA and New England anomaly

We are not confident about

anomaly 3


Lightning parameterization

  • needs to be consistent with parameterized convection
  • Flash rate parameterization
  • Average NO production per flash
  • Vertical distribution (Pickering et al. 1998)

cloud top height, convective precipitation rate, upward cloud mass flux

our lightning parameterization
Our lightning parameterization
  • Combining NLDN (Cummins et al., 1998) flash rates with climatological IC/CG ratios (Boccippio et al., 2001), it is possible to estimate total U.S. flash rates.

total flash rate is proportional to (zmmu – threshold)**2

  • The lightning flashes are further scaled for each month to match:
  • OTD/LIS (climatology),
  • NLDN CG (year specific) * Z (IC:CG climatology)

and 44 flashes/second globally – consistent with OTD/LIS climatology (Christian et al. 2003)

- 240 moles NO/flash everywhere (close to Huntrieser et al 2007)

- 480 moles NO/flash in midlatitudes (close to Ott et al. 2008 – constraint by anvil aircraft obs)

  • 500 used in Hudman et al. 2007 showed better agreement with aircraft obs – however it was still low!

Constraining total flashrates to OTD/LIS, NLDN*Z




(Z = IC / CG)

Total flashrate per 2x2.5 grid box per minute

Updraft mass flux

[Pa s-1]

Input for



Constraining total flashrates to OTD/LIS, NLDN*Z




(Z = IC / CG)

Updraft mass flux

[Pa s-1]



Input for



Constraining total flash rates to OTD/LIS, NLDN*Z




(Z = IC / CG)

Note a large difference between

LIS/OTD and NLDN*Z field

Updraft mass flux

[Pa s-1]



Input for


concluding remarks na pollutant export
Concluding remarks: NA pollutant export
  • To investigate NA pollutant export, emission inventory has to be as accurate as possible, we are doing the difference (with anthro CTM run – w/o anthro run)
  • Important role plays also the lightning NOx (longer chemical lifetimes aloft and greater wind speeds can then lead to significant large-scale transport)
  • First look showed that the RF (as convenient measure of pollutant export) was interestingly larger in summer 2004 than in summer 2002.

- stronger convection in 2004 ?? (zmmu+hketa significantly larger only in May – not shown), pollutant transport to UT- enhanced lightning NOx production ?? (due to deep convection, instability)

?? both lightning and convection is parameterized, we only tune LP since we have observations available (NLDN, OTD/LIS)

- enhanced forest fires over Canada and Alaska 2004, more UT O3 (Pfister et al. 2005)

  • What’s next?
what s next
What’s next?
  • Is the use of Z ratio climatology reasonable (gives high total flash rates)??
  • Z ratios are based on OTD/LIS – years 1995-1999. How large is the interannual variability in OTD/LIS data??
  • Should be Z ratio climatology updated – should we spend the money for the new instrument (currently LIS observes lightning only in 35 degrees South and 35 degrees North latitude)?? Recall that based on the current Z ratio climatology: in the summer half of the lightning occurs over the US!!
  • Decide what to use in order to constrain the model calculated total flash rates (model uses cloud mass flux from reanalyzed metfields)
  • Look directly at NO, NOx INTEX aircraft profiles rather than at ozone-sondes profiles
  • Separate the individual signals: meteorology (lightning), anthro emissions (‘cross’ simulations’)
  • Recalculate the RF fields