P43  Parameterizing Lightning-Generated NOx at Resolutions with       Convective Parameterization for Upper Tropospheric Ozone Simulations

Wong, John, The University of Colorado, Boulder, and Mary Barth, NCAR, and David Noone, The University of Colorado, Boulder

Upper tropospheric ozone has been shown to be sensitive to lightning-generated NOx (LNOx), especially during monsoon seasons when an upper-air anticyclone forms providing a region in which ozone precursors are accumulated over an extended period of time. The parameterization of LNOx emissions in chemistry transport models (CTMs) is based on three parts: 1) prediction of lightning flash rate based on model variables, 2) prediction of the intracloud to cloud-to-ground flash ratio based on model variables to locate the LNOx emission altitudes, and 3) estimation of the amount of NO produced per flash. In this study, we evaluate the ability of the widely-used Price and Rind (1992) lightning flash rate parameterization, which is based on cloud-top height, using the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) by comparing model-predicted lightning flashes with data from the National Lightning Detection Networks (NLDN) and from the Earth Networks Total Lightning Networks (ENTLN) for the contiguous United States. The WRF-Chem model reasonably predicts both integrated total and CG flash counts at 36 km resolution when compared against observational data for summer 2006 and 2011. However, the Price and Rind (1993) IC:CG ratio parameterization, which is based on the depth of the cold cloud, does not give IC:CG ratios similar to those determined from the ENTLN observations. Further, when WRF-Chem was run at 12 km horizontal resolution, the Price and Rind (1994) resolution dependency factor did not scale well to produce similar lightning flash frequency. Based on these results, recommendations are made regarding any further utilization of the Price and Rind parameterizations. WRF-Chem sensitivity simulations are also being conducted to estimate the influence of LNOx on ozone during the North American monsoon period. The model results are evaluated with data sets from satellite-borne and balloon-borne instruments, and their sensitivities to varying levels of NO per flash and other parameters are quantified in this study.