Mid-Latitude Lightning NOx Production from OMI and WWLLN Data
Thursday, 17 December 2015: 10:35
3008 (Moscone West)
Mid- and upper- tropospheric NOx (NO + NO2) is a trace gas important in atmospheric radiative forcing through its regulation of ozone concentrations. Changes in NOx and ozone result in indirect effects on other greenhouse gases such as methane. Lightning is the dominant source of NOx in the free troposphere, and most estimates of the concentration of lightning NOx (LNOx) require knowledge of the amount of this species produced per lightning flash. We present the largest spatial- and temporal-scale investigation of LNOx to date that combines satellite-based NOx estimates and lightning flash data. The data comprise five northern-hemisphere (NH) summers, including much of the mid-latitude regions in North America and Asia and adjacent waters. NO2 measurements from the Ozone Monitoring Instrument (OMI), selected from cloudy areas, are converted to LNOx and compared with flashes preceding OMI overpass by 1 – 4 hours. The flash counts are derived from ground-based World Wide Lightning Location Network (WWLLN) data that are adjusted for detection efficiency by comparing them with Optical Transient Detector and Lightning Imaging Sensor satellite data. We find reasonable correlation between the number of lightning flashes and the amount of LNOx produced and estimate mean efficiencies for the production of LNOx in various NH regions. Overall results indicate mole/flash values near the low end of those reported in previous LNOx studies, as well as a possible dependence of production efficiency on flash rate. These findings have potential implications for upper tropospheric trace gases and the global NOx budget.