Remote sensing ‘ground-based automatic UV / visible spectrometer’ for the study of atmospheric trace gases

Abstract

An advance remote sensing instrument, the ‘ground-based automatic UV / visible spectrometer’, has been developed indigenously at Pune (18° 31′ N, 73° 55′ E) to cover the spectra (462–498 nm) of zenith sky scattered light. A spectrometry technique is used to find out the vertical column density (VCD) of many atmospheric trace gases, such as NO₂, O₃, H₂O and O₄. The VCDs of these gases are extracted from observed spectra by comparing the magnitude of the differential optical depth (DOD) of each species in the 462–498 nm spectral range. Slant column densities (SCDs) of each species are found to increase with solar zenith angle (SZA), due to the approaching higher path length of sunlight. The VCDs of O₃ and NO₂ derived by the UV / visible spectrometer are compared with the ozone monitoring instrument (OMI) Aura satellite and ground-based Brewer spectrometer data. The compared VCD values are found to be close to satellite and ground-based measurements.

Acknowledgements

The authors are grateful to Professor B.N. Goswami, Director, IITM, and Dr. P.C.S. Devara, Head of PM&A division, for their encouragement. The authors are also grateful to the OMI satellite team for providing data at the site, and to the Department of Science and Technology, New Delhi, Government of India for the financial support during the tenure of this work.