NASA Decision Support: Monitoring Air Quality Effects of Anthropogenic Emissions Reductions and Estimating Emissions from Natural Sources
May 14, 2013 16:46:16
Description of Problem
An accurate specification of anthropogenic and natural emissions is crucial for determining the impact of emission perturbations on air quality. However, lightning-NO emissions, a substantial contributor to tropospheric NO2 columns over the United States during the summertime, are not included in the Community Multiscale Air Quality (CMAQ) model used by the Environmental Protection Agency. A goal of this project is to add lightning-NO emissions to CMAQ. Simulations with lightning-NO emissions will provide more accurate estimates of nitrogen deposition and will be useful for top down estimates of anthropogenic emissions. A second goal of this project is to use tropospheric nitrogen dioxide (NO2) columns retrieved from the Ozone Monitoring Instrument aboard NASA’s Aura satellite to refine emissions of nitric oxide (NO) by microbial activity in soils calculated by the Biogenic Emission Inventory System (BEIS) that is used within the EPA’s Community Multiscale Air Quality Model (CMAQ). The lightning-NO portion of this project is supported under this Grant.
Scientific Objectives and Approach
Lightning-NO emissions in the CMAQ model will be parameterized using a previously developed method that utilizes the relationship between flash rate and convective precipitation rate. The resulting flash rate distribution will be scaled so that the monthly average model-calculated flash rate matches the observed monthly average flash rate where the “observed” flash rate is determined by scaling National Lightning Detection Network (NLDN) cloud-to-ground (CG) flash rates by climatological IC (intracloud)/CG ratios.
CMAQ simulations will be run with the improved source distributions for lightning-NO. Results will be evaluated and the resulting algorithms will be included as options in future releases of CMAQ.
During the first two years of this project, lightning-NO emissions were prepared for use in CMAQ simulations designed to study the impact of lightning-NO production on tropospheric photochemistry, surface air quality, and nitrogen deposition during the summers of 2004 and 2006.
During year three of this project, we provided a nearly final version of this algorithm to EPA. We are currently working with EPA personnel as they implement this algorithm into CMAQ. It is expected to be available to the scientific community with the next release of CMAQ. We are also analyzing the results of the CMAQ simulations and preparing a paper on our results. As part of this analysis, we are studying the impact of lightning-NO production on wet deposition of oxidized nitrogen over the eastern United States (longitudes east of 100° W). Figures 1a-d compare wet deposition rates from National Acid Deposition Program (NADP) monitoring sites to modeled deposition rates for simulations without (left) and with (right) lightning-NO production and for simulations with unadjusted (top) and adjusted (bottom) precipitation rates. Model-calculated wet deposition is 27.5% too low without lightning-NO production (Figure 1a). Adding lightning-NO production eliminates this low-bias (Figure 2b). However, the resulting fit shows considerable scatter (RMSc=0.13) and correlations between model-calculated and NADP-measured deposition rates are only moderate (R = 0.50). The scatter is reduced and correlations improve when adjustments are made for biases in modeled precipitation with respect to NADP-measured precipitation. When these adjustments are made, RMSc decreases to 0.10 and the correlation increases to 0.76 (Figure 1d).
In the final year of this project, we will finalize the algorithm and work with pilot users at EPA. We will also finalize a research paper that uses the algorithm to study the impact of lightning-NO production on tropospheric photochemistry over the United States.
Other Publications and Conferences
Allen, D. J., K. Pickering, R. Pinder, B. Henderson, W. Koshak, and T. Pierce, Impact of lightning-NO emissions on eastern United States photochemistry during the summer of 2006 as determined using the CMAQ model, 2011 AMS meeting, Seattle, WA.
Allen, D. J., K. Pickering, R. Pinder, B. Henderson, W. Koshak, and T. Pierce, Impact of lightning-NO emissions on eastern United States photochemistry during the summer of 2006 as determined using the CMAQ model, 2010 CMAS meeting, Chapel Hill, NC.
Allen, D. J., K. Pickering, R. Pinder, and T. Pierce, 2010: Impact of lightning-NO emissions on eastern United States photochemistry determined using the CMAQ model. 2010 AMS Meeting, Atlanta, GA.
Allen, D. J., K. Pickering, R. Pinder, and T. Pierce, 2009: Impact of lightning-NO emissions on eastern United States photochemistry during the summer of 2004 as determined using the CMAQ model. 2009 CMAS meeting, Chapel Hill, NC.