Federal, state and local air quality agencies use the U.S. Environmental Protection Agency (EPA) Community Multiscale Air Quality (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 commercial and government industries forced to comply with the standards. Costly health, environmental and socioeconomic problems can result from concentration underestimates.

We describe a robust NASA lightning model to obtain a realistic representation of lightning NOx (= NO + NO2) emissions for the CMAQ model. Currently, emissions from lightning are either omitted or are poorly represented in CMAQ. 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 with field campaign and laboratory results. It uses NASA satellite lightning data in conjunction with ground-based lightning detection systems to assure that a realistic representation of lightning is obtained. Special attention is given to several important lightning variables including: the frequency and geographical distribution of lightning, lightning channel length, channel altitude, channel peak current, and the number of strokes per flash.