Impact of lightning-NO on eastern United States photochemistry during the summer of 2006 as determined using the CMAQ model D. J. Allen1, K. E. Pickering2, R. W. Pinder3, B. H. Henderson4, K. W. Appel3, and A. Prados5 1Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD, USA 2Atmospheric Chemistry and Dynamics Laboratory, Code 614 NASA-Goddard, Greenbelt, MD, USA 3Atmospheric Modeling and Analysis Division, US EPA, Research Triangle Park, NC, USA 4University of North Carolina Chapel Hill, NC, USA 5Joint Center for Earth Sciences Technology (JCET), University of Maryland Baltimore County, Baltimore, MD, USA
Abstract. A lightning-nitrogen oxide (NO) algorithm is implemented in the Community
Multiscale Air Quality Model (CMAQ) and used to evaluate the impact of
lightning-NO emissions (LNOx) on tropospheric photochemistry over the
United States during the summer of 2006.
For a 500 mole per flash lightning-NO source, the mean summertime
tropospheric NO2 column agrees with satellite-retrieved columns to
within −5 to +13%. Temporal fluctuations in the column are moderately
well simulated; however, the addition of LNOx does not lead to a better
simulation of day-to-day variability. The contribution of lightning-NO to
the model column ranges from ∼10% in the northern US to >45%
in the south-central and southeastern US. Lightning-NO adds up to 20 ppbv to
upper tropospheric model ozone and 1.5–4.5 ppbv to 8-h maximum surface
layer ozone, although, on average, the contribution of LNOx to model
surface ozone is 1–2 ppbv less on poor air quality days. LNOx increases
wet deposition of oxidized nitrogen by 43% and total deposition of
nitrogen by 10%. This additional deposition reduces the mean magnitude of
the CMAQ low-bias in nitrate wet deposition with respect to National
Atmospheric Deposition monitors to near zero.
Differences in urban/rural biases between model and satellite-retrieved
NO2 columns were examined to identify possible problems in model
chemistry and/or transport. CMAQ columns were too large over urban areas.
Biases at other locations were minor after accounting for the impacts of
lightning-NO emissions and the averaging kernel on model columns.
In order to obtain an upper bound on the contribution of uncertainties in
NOy chemistry to upper tropospheric NOx low biases, sensitivity
calculations with updated chemistry were run for the time period of the
Intercontinental Chemical Transport Experiment (INTEX-A) field campaign
(summer 2004). After adjusting for possible interferences in NO2
measurements and averaging over the entire campaign, these updates reduced
7–9 km biases from 32 to 17% and 9–12 km biases from 57 to 46%. While
these changes lead to better agreement, a considerable unexplained NO2
low-bias remains in the uppermost troposphere.
Citation: Allen, D. J., Pickering, K. E., Pinder, R. W., Henderson, B. H., Appel, K. W., and Prados, A.: Impact of lightning-NO on eastern United States photochemistry during the summer of 2006 as determined using the CMAQ model, Atmos. Chem. Phys., 12, 1737-1758, doi:10.5194/acp-12-1737-2012, 2012.