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Modeling Lightning NOx Emissions over the Contiguous United States and the Northern Hemisphere with NLDN and WWLLN data
Citation:
Kang, D., M. Madden, C. Hogrefe, G. Sarwar, R. Mathur, AND B. Henderson. Modeling Lightning NOx Emissions over the Contiguous United States and the Northern Hemisphere with NLDN and WWLLN data. 103rd Annual AMS Conference, Denver, CO, January 08 - 12, 2023.
Impact/Purpose:
Lightning is one of the major natural sources to produce nitrogen oxides (NOx) which contribute to the tropospheric ozone (O3) formation and other air quality related processes. It is important to incorporate the most up-to-date science and observational data for lightning NOx productions in time and space in air quality models. This research is to investigate the burden of LNOx emissions over the contiguous United States and the Northern Hemisphere using lightning flash data from ground-based networks and the climatological LNOx emissions in the Global Emissions InitiAtive (GEIA) dataset.
Description:
Lightning induced nitrogen oxides (LNOx) emissions are estimated to be in the range of 2 to 8 Tg N yr−1 and contribute 10-15% of the total global NOx emissions budget derived through limited observational and modeling approaches. The 2 to 8 Tg N yr-1 range has become a de facto constraint for LNOx emissions allocation of a constant total (e.g., 5 Tg N yr−1) in many global modeling studies. We analyze the impact of using lightning flash data observed by the National Lightning Detection Network (NLDN) and World Wide Lightning Location Network (WWLLN) as input to the Community Multiscale Air Quality (CMAQ) model’s inline LNOx emissions module. We apply CMAQ over the contiguous United States (CONUS) and Northern Hemisphere to analyze the spatial and temporal distributions of LNOx emissions and the contributions to the nitrogen oxide (NOx) budget. Comparisons to the LNOx emissions in the Global Emissions InitiAtive (GEIA) dataset are made to examine the differences and similarities between the observation-based dynamic emissions and the static climatology-based emissions inventory in latitudinal and regional distributions. Preliminary results indicate that the GEIA LNOx emissions are comparable to the observation-based LNOx emissions in North America and Europe (when the WWLLN lightning flashes are scaled by those from NLDN), but large differences are present in other regions. In generating LNOx emissions, large uncertainty is associated with lightning production efficiency, a parameter used to convert lightning flashes into LNOx emissions. Our estimates of LNOx emissions over different regions fall with the range of values reported in the recent literature for modeling studies on LNOx impact on air quality. Taking advantage of the EPA’s Air QUAlity TimE Series (EQUATES) project, we investigate decadal-scale trends in the relative contribution of the regional to hemispheric LNOx burdens to total NOx emissions in the context of decreasing trends of anthropogenic NOx emissions.