ATMOSPHERIC NO3 OBSERVATIONS OVER LOW-LATITUDE NORTHERN-HEMISPHERE DURING NIGHT

Nighttime column abundance of NO3 has been measured in the low latitude region by visible absorption spectroscopy technique. For that, direct moonlight irradiance on the surface of the Earth has been measured near full Moon in the 655.0- to 667.0-nm region. Errors due to solar Fraunhofer effect, atmospheric aerosol and Rayleigh scattering, atmospheric water vapor and ozone contents have been removed. High zenith angle direct solar spectrum and low zenith angle lunar spectrum have been used as background spectra. The vertical column abundance of NO3 was found to be about 10 times higher than that reported earlier by others for a low latitude region.