This project supports the Air Quality application area of the NASA Applied Sciences Program. A robust NASA lightning model will be applied to obtain a realistic representation of lightning NOx (= NO + NO2) emissions for the Community Multiscale Air Quality (CMAQ) model. Currently, emissions from lightning are either omitted or are poorly represented; this reduces the accuracy of CMAQ model predictions of important trace gases linked to NOx emissions, such as ozone. The NASA lightning model optimally combines state-of-the-art lightning measurements (including NASA satellite lightning observations) with field campaign and laboratory results to assure that a realistic representation of lightning is obtained. Special attention is given to several important variables: the frequency and geographical distribution of lightning, lightning channel length, channel altitude, channel peak current, and the number of strokes per flash. To assess improvements to CMAQ, the lightning model and associated lightning data will be applied to a baseline CMAQ run for the continental US for the calendar year 2006. Federal, state and local air quality agencies use the U.S. Environmental Protection Agency (EPA) CMAQ modeling system to determine compliance with the National Ambient Air Quality Standards (NAAQS). Because emission reduction scenarios are tested using CMAQ with an aim of determining the most efficient and cost effective strategies for attaining the NAAQS, it is very important that trace gas concentrations derived by CMAQ are accurate. Overestimating concentrations can literally translate into billions of dollars lost by industries forced to comply with the standards. Costly health, environmental and socioeconomic problems can result from concentration underestimates. We hypothesize that this project will show improvement in CMAQ trace gas concentration predictions over various regions (e.g., eastern United States). We anticipate that these improvements will have a direct impact on decision makers responsible for establishing the NAAQS and assuring its compliance.