Tropospheric Ozone Production from Lightning

As part of the INTEX Ozonesonde Network 2006 Study (IONS-06) ozonesondes were launched from a network of 22 stations stretching from Mexico to Canada in August and September of 2006. Vertical profiles of ozone, temperature and relative humidity were measured up to altitudes that usually exceeded 30 km. The ozone profiles from four of these stations, Barbados, Mexico City, the Ron Brown and Houston, have been evaluated with respect to lightning events that take place upwind of the profiles. The lightning is measured with the World Wide Lightning Location (WWLL) Global Network.The ozone profiles at each location were averaged over the entire measurement period and the standard deviations calculated as a function of altitude. Deviations from the averages, for each station, were calculated for the individual sounding and divided by the standard deviation to provide vertical profiles of ozone anomalies.Eighteen hour back trajectories were calculated using the NOAA HYSPLIT program to determine the history of the air mass that arrived at 10 different altitudes through which the individual sondes passed. At each hour in a back trajectory, the location was compared with the lightning frequency data base for that day and the number of lightning events, if any, was determined. Anomalies in ozone of greater than one standard deviation from the average are compared to the number of lightning events upwind and their distance from the location of the ozone measurements. A clear, positive correlation is seen between positive ozone anomalies and the frequency of lightning events.