<title>Measurement of atomospheric nitrogen dioxide column density by solar spectroscopic method</title>

Abstract

Nitrogen Dioxide (NO₂) column density was studied by solar spectroscopic method. In the retrieval of NO₂ column density the Kitt Peak Solar Flux Atlas provides a standard reference of the extraterrestrial solar spectrum. However in order to eliminate the Fraunhofer features from the solar spectrum the ground-level solar spectrum needs to be re-scaled for wavelength correction and resolution matching to the reference Kitt Peak Solar spectrum. The analysis procedure becomes much simplified if both the reference and the ground-level solar spectra are captured by the same instrument. A portable miniature charge-coupled device (CCD) spectrometer was employed to acquire both the reference and ground-level solar spectra. The reference spectrum was captured in Xinjiang (42.107°N 83.750°E), the People's Republic of China during a flight in a plane. The altitude ofthe reference solar spectrum is 11 meters above the sea level. The ground-level solar spectrum was acquired in the campus of City University of Hong Kong (22.336°N, 114.173°E) using a computer-controlled solar tracker. By analyzing the solar spectra obtained at two different locations and altitudes NO₂ total column density can be deduced.