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On the Relationship Between Observed NLDN Lightning Strikes and Modeled Convective Precipitation Rates: Parameterization of Lightning NOx Production in CMAQ
Citation:
Kang, D., N. Heath, K. Foley, J. Bash, S. Roselle, AND R. Mathur. On the Relationship Between Observed NLDN Lightning Strikes and Modeled Convective Precipitation Rates: Parameterization of Lightning NOx Production in CMAQ. Chapter 65, Air Pollution Modeling and its Application XXV. Springer International Publishing AG, Cham (ZG), Switzerland, , 413-419, (2018).
Impact/Purpose:
The Community Multiscale Air Quality Model (CMAQ) parameterizes the lightning NO emissions using local scaling factors adjusted by the convective precipitation rate that is predicted by the upstream meteorological model; the adjustment is based on the observed lightning strikes from the National Lightning Detection Network (NLDN). For this parameterization to be valid, the existence of an a priori reasonable relationship between the observed lightning strikes and the modeled convective precipitation rates is needed. In this study, we present an analysis leveraged on the observed NLDN lightning strikes and the Weather Research and Forecasting (WRF) model (the model used to create meteorological inputs for CMAQ) simulations over the continental United States for a time period spanning over a decade. Based on the analysis, new parameterization scheme for lightning NOX is proposed and the results are being evaluated. The proposed scheme will be beneficial to modeling exercises where the observed lightning strikes are not generally available, such as air quality forecasts. Results show distinctive spatial patterns for the relationship between observed lightning strikes and modeled convective precipitation rates over the continental United States. Based on this analysis, a reasonable parameterization for the lightning NOX production and distribution for use in regional air quality models are developed.
Description:
In the middle and upper troposphere, lightning is the most important source of nitrogen oxides (NO X = NO + NO 2), which play an essential role in the production of ozone (O 3) and influence the oxidizing capacity of the troposphere (Murray 2016). Despite much effort in both observing and modeling lightning NO X during the past decade, considerable uncertainties still exist with the quantification of lightning NO X (LTNOX) production and distribution in the troposphere. Further, it is challenging for regional chemistry and transport models to parameterize LTNOX production and distribution in time and space accurately. Most studies estimate global LTNOX production ranging from 2 to 8 Tg (N) year −1 or about 10–15% of the total NO x budget (Pickering et al. 2014). However, owing to the concerted effort to reduce anthropogenic NO x emissions in recent decades, it is expected that the relative burden of LTNOX and its associated impact on atmospheric chemistry will increase. As a result, it is important to include LTNOX even when modeling ground level air quality and the interaction of air-surface exchange processes.
