Impact of lightning-NO on eastern United States photochemistry during the summer of 2006 as determined using the CMAQ model

Abstract

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 (LNO x ) 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 NO 2 column agrees with satelliteretrieved columns to within −5 to +13 %. Temporal fluctuations in the column are moderately well simulated; however, the addition of LNO x 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 LNO x to model surface ozone is 1-2 ppbv less on poor air quality days. LNO x 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 NO 2 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 NO y chemistry to upper tropospheric NO x 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 NO 2 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 NO 2 low-bias remains in the uppermost troposphere.

First estimates of global free-tropospheric NO<sub>2</sub> abundances derived using a cloud-slicing technique applied to satellite observations from the Aura Ozone Monitoring Instrument (OMI)

“…The profile shapes suggest that NO 2 sources, presumably lightning, are located primarily in the upper troposphere in these regions. This is consistent with aircraft measurements (e.g., Huntrieser et al, 2009) and modeling studies (e.g., Allen et al, 2010Allen et al, , 2012Martini et al, 2011) of lightning-generated NO x . In contrast, NO 2 VMR profiles are more uniform in winter, possibly owing to less frequent lightning activity associated with convection in the shifting intertropical convergence zone (ITCZ).…”

“…C1 in Appendix C) in these regions are indicative of frequent convection. In particular, extensive enhancements in summertime NO 2 VMRs over NH tropical and subtropical oceans, are similar to modeled lightning NO x enhancements in previous studies (e.g., Choi et al, 2008;Allen et al, 2012;Martini et al, 2011;Walker et al, 2010). This suggests that lightning is a major source of freetropospheric NO 2 in tropical and subtropical regions in summer.…”

“…Model studies show that lightning NO x production contributes to free-tropospheric NO 2 abundances, but magnitudes and distributions are still largely unknown; in particular, vertical distributions of lightning NO x are dependent upon the characteristics of the convection parameterizations in the models (Choi et al, 2005(Choi et al, , 2008Allen et al, 2012;Martini et al, 2011). The NO 2 lifetime in the free troposphere (up to a week or more) allows for intercontinental transport of uplifted anthropogenic and lightning-generated NO 2 (e.g., Li et al, 2004;Wang et al, 2006;Zhang et al, 2008;Walker et al, 2010).…”

Multi-year downscaling application of two-way coupled WRF v3.4 and CMAQ v5.0.2 over east Asia for regional climate and air quality modeling: model evaluation and aerosol direct effects

“…Soil NO x emissions were also calculated by the in-line BEIS3 module. Lightning NO x emissions were inline calculated by estimating the number of lightning flashes based on the simulated convective precipitation (Allen et al, 2012).…”

Urban Emissions and Regional Air Quality in India

“…India, in the tropics, is prone to a significant number of annual lightning flashes across the entire country, including regions which already exhibit a high bias compared to OMI [Cecil et al, 2014]. However, regional average low biases between OMI NO 2 tropospheric columns and regional and global chemistry models are common [Allen et al, 2012;Kemball-Cook et al, 2015]. In the case of this study, we find that low biases exist in many Eq.…”