Harold Peterson

Variability of CONUS Lightning in 2003–12 and Associated Impacts

AbstractChanges in lightning characteristics over the conterminous United States (CONUS) are examined to support the National Climate Assessment (NCA) program. Details of the variability of cloud-to-ground (CG) lightning characteristics over the decade 2003–12 are provided using data from the National Lightning Detection Network (NLDN). Changes in total (CG + cloud flash) lightning across part of the CONUS during the decade are provided using satellite Lightning Imaging Sensor (LIS) data. The variations in NLDN-derived CG lightning are compared with available statistics on lightning-caused impacts to various U.S. economic sectors. Overall, a downward trend in total CG lightning count is found for the decadal period; the 5-yr mean NLDN CG count decreased by 12.8% from 25 204 345.8 (2003–07) to 21 986 578.8 (2008–12). There is a slow upward trend in the fraction and number of positive-polarity CG lightning, however. Associated lightning-caused fatalities and injuries, and the number of lightning-caused wild...

The kinematic and microphysical control of lightning rate, extent, and NOX production

The purpose of this study is to investigate the kinematic and microphysical control of lightning properties, particularly those that may govern the production of nitrogen oxides via lightning (LNOx), such as flash rate, type and extent. The NASA Lightning Nitrogen Oxides Model (LNOM) is applied to lightning observations following ordinary convective cells through their lifecycle. LNOM provides estimates of flash rate, flash type, channel length distributions, lightning segment altitude distributions (SADs) and LNOX production profiles. For this study, LNOM is applied in a Lagrangian sense to multicell thunderstorms over Northern Alabama on 21 May 2012 during the Deep Convective Clouds and Chemistry (DC3) experiment. The LNOM lightning characteristics and LNOx production estimates are compared to the evolution of updraft and precipitation properties measured from a dual-Doppler and polarimetric radar network.

A Return Stroke NOx Production Model

AbstractA model is introduced for estimating the nitrogen oxides (NOx = NO + NO2) production from a lightning return stroke channel. A realistic modified transmission line model return stroke current is assumed to propagate vertically upward along a stepped leader channel of 0.1-cm radius. With additional assumptions about the initial radial expansion rate of the channel, the full nonlinear differential equation for the return stroke channel radius r(z, t) is solved numerically using Mathematica V9.0.1.0. Channel conductivity and channel air density are adjustable constants, and the model employs typical atmospheric profiles of temperature, pressure, and density. The channel pressure is modeled by a dynamic pressure expression. Channel temperature is extracted from the pressure by a minimization technique that involves a generalized gas law appropriate for high temperatures where dissociation and ionization are important. The altitude and time variations of the channel energy density are also obtained. Th...