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 E xperiment (HALOE) on the Upper Atmosphere Research Satellite (UARS) is anal yzed for the entire year of 1993 and compared to the seasonal and global li ghtning distributions inferred from the Optical Transient Detector (OTD). T he results suggest a link between lightning activity and observed high leve ls of NO2 in the upper troposphere and lower stratosphere. Enhanced NO2 mix ing 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 So uthern Hemispheres. Moreover, the results show that background levels of NO 2 mixing ratios generally correspond to areas of little or no lightning act ivity.