Nitrogen oxides (NOx) produced by lightning (LNOx) play an important role in atmospheric chemistry, including the formation of tropospheric ozone (O3). Chemical transport models such as the Weather Research and Forecasting (WRF-Chem) model can simulate some aspects of ozone chemistry, but to produce accurate O3 concentrations, it is important to accurately specify the LNOx. WRF-Chem currently only includes lightning and the production of the resulting NOx when run at cloud scale resolution. These cloud scale parameterizations are based on previous studies that have shown that lightning flash rate is strongly correlated with radar-derived storm height, updraft strength, the vertical flux of ice, and other storm parameters. We will describe a new way to parameterize lightning occurrence and the formation of LNOx when WRF-Chem is run at the regional scale (e.g., 36 or 12 km).

We present a comparison of three regional scale lightning parameterizations during NASA's Intercontinental Chemical and Transport Experiment (INTEX-A, 2004). Two of the parameterizations use previously reported relations between lightning flash rate and radar-derived storm top height. We recently developed the third parameterization which uses a relationship between convective precipitation, depth of the mixed phase layer, and flash rate.

The predicted flash rates and a NOx production term determine the two dimensional pattern of LNOx. The LNOx then is vertically distributed using our previously calculated climatological vertical distributions of lightning sources measured by the Lightning Detection and Ranging (LDAR) network at Kennedy Space Center that are functions of storm top.

Results from the three regional scale lightning NOx parameterizations are presented and validated using NLDN total lightning data as well as in situ NOx observations from five INTEX-A flights.