Impact of Lightning-NO Emissions on Eastern United States NOx and O3 Determined Using the CMAQ Model
Abstract
Production of NO by lightning (LNOx) is an important part of the summertime tropospheric NOx budget over the United States, but it is also its most uncertain component. Global model simulations indicate that LNOx increases summertime upper tropospheric NOx mixing ratios over the eastern United States by 60-75%. A regional simulation with the Community Multiscale Air Quality Model (CMAQ) that did not include lightning-NO emissions greatly underestimated upper tropospheric NOx concentrations measured during NASA’s INTEX-A field campaign. These large biases made it difficult to constrain ground-level NOx emissions using SCIAMACHY retrievals and CMAQ output. A lightning-NO parameterization has been developed that can be used with the CMAQ model. Flash rates in this scheme are assumed to be proportional to convective precipitation rates from the driving meteorological model (MM5 or WRF) and scaled so that monthly average flash rates in each grid box match National Lightning Detection Network (NLDN) observed flash rates after adjusting for climatological intracloud to cloud-to-ground (IC/CG) ratios. Production of 500 moles of NOx is assumed per flash, which results from cloud-resolved simulations of individual midlatitude and subtropical thunderstorm constrained by aircraft observations. The LNOx emissions are distributed in the vertical according to the climatological histogram of VHF lightning sources from Lightning Mapping Arrays. The contribution of lightning-NO emissions to eastern United States NOx and ozone distributions during the summers of 2004 and 2006 will be evaluated by comparing results of CMAQ simulations with and without lightning-NO emissions to measurements from aircraft field campaigns, to ozone profiles from the IONS ozonesonde campaigns, and to satellite NO2 retrievals from the SCIAMACHY and OMI satellite instruments.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.A31D0130P
- Keywords:
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- 0322 ATMOSPHERIC COMPOSITION AND STRUCTURE / Constituent sources and sinks;
- 0365 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: composition and chemistry;
- 0368 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: constituent transport and chemistry;
- 3324 ATMOSPHERIC PROCESSES / Lightning