Airborne quantification of upper tropospheric NOx production from lightning in deep convective storms over the United States Great Plains

The reported range for global production of nitrogen oxides (NOx = NO + NO₂) by lightning remains large (e.g., 32 to 664 mol NOx flash⁻¹), despite incorporating results from over 30 individual laboratory, theoretical, and field studies since the 1970s. Airborne and ground-based observations from the Deep Convective Clouds and Chemistry experiment in May and June 2012 provide a new data set for calculating moles of NOx produced per lightning flash, P(NOx), in thunderstorms over the United States Great Plains. This analysis utilizes a combination of in situ observations of storm inflow and outflow from three instrumented aircraft, three-dimensional spatial information from ground-based radars and satellite observations, and spatial and temporal information for intracloud and cloud-to-ground lightning flashes from ground-based lightning mapping arrays. Evaluation of two analysis methods (e.g., a volume-based approach and a flux-based approach) for converting enhancements in lightning-produced NOx from volume-based mixing ratios to moles NOx flash⁻¹ suggests that both methods equally approximate P(NOx) for storms with elongated anvils, while the volume-based approach better approximates P(NOx) for storms with circular-shaped anvils. Results from the more robust volume-based approach for three storms sampled over Oklahoma and Colorado during DC3 suggest a range of 142 to 291 (average of 194) moles NOx flash⁻¹ (or 117-332 mol NOx flash⁻¹ including uncertainties). Although not vastly different from the previously reported range for storms occurring in the Great Plains (e.g., 21-465 mol NOx flash⁻¹), results from this analysis of DC3 storms offer more constrained upper and lower limits for P(NOx) in this geographical region.