Global distributions of OH and O2 (1.27 μm) nightglow emissions observed by TIMED satellite

In order to investigate the global distributions of temporal variations of OH and O2 nightglow emissions, we statistically analyzed their variations with altitude, local time, and season, using the OH and O2 airglow emission rate data observed by the TIMED satellite between 2002 and 2009. The results indicated that the OH nightglow emission was stronger than dayglow emission and the O2 nightglow emission was weaker than dayglow emission. In the tropics, the OH nightglow intensity reached its maximum near midnight; at higher latitudes, the OH nightglow intensities after sunset and before sunrise were much strong. At the equinoxes, the O2 nightglow intensity in the tropics decreased with local time; at the solstices, the local time-latitude distribution of the O2 nightglow intensity had a valley (with weak emission). As for the altitude-latitude distributions of nightglow emission rates, the distribution for OH nightglow at the equinoxes had one peak (with strong emission) at the equator, with a peak height around 85 km; the peak for the March equinox was stronger than that for the September equinox. The distribution for O2 nightglow at the equinoxes had three peaks, lying at 30° in the spring and autumn hemispheres and at the equator, and the peak height at the equator was the lowest. The distributions for both OH and O2 nightglow emissions at the solstices had three peaks. Both nightglow intensities in the tropics had obvious annual and semi-annual variations, the peaks and valleys for semi-annual variations appeared near the equinoxes and solstices, respectively, and the peak at the March equinox was larger than that at the September equinox. The distributions of both OH and O2 nightglow intensities showed a hemispheric asymmetry.