Enhanced NOx by lightning in the upper troposphere and lower stratosphere inferred from the UARS global NO2 measurements

This paper reveals a possible connection between lightning activity and the UARS NO2 data on a global scale. NO2 measured by the Halogen Occultation Experiment (HALOE) on the Upper Atmosphere Research Satellite (UARS) is analyzed for the entire year of 1993 and compared to the seasonal and global lightning distributions inferred from the Optical Transient Detector (OTD). The results suggest a link between lightning activity and observed high levels of NO2 in the upper troposphere and lower stratosphere. Enhanced NO2 mixing ratios significantly above the background level are consistently found in areas of elevated lightning activity. This relation is strongest in the tropical regions during the summer and spring months of the Northern and Southern Hemispheres. Moreover, the results show that background levels of NO2 mixing ratios generally correspond to areas of little or no lightning activity.