Measurement of atomospheric nitrogen dioxide column density by solar spectroscopic method

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.