Retrieval of stratospheric O3 and NO2 vertical profiles using zenith scattered light observations

G. S. Meena, C. S. Bhosale, D. B. Jadhav
2006 Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences  
Daily zenith scattered light intensity observations were carried out in the morning twilight hours using home-made UV-visible spectrometer over the tropical station Pune (18 • 31 , 73 • 51 ) for the years 2000-2003. These observations are obtained in the spectral range 462-498 nm for the solar zenith angles (SZAs) varying from 87 • to 91.5 • . An algorithm has been developed to retrieve vertical profiles of ozone (O 3 ) and nitrogen dioxide (NO 2 ) from ground-based measurements using the
more » ... e iteration method. This retrieval method has been checked using measured and recalculated slant column densities (SCDs) and they are found to be well matching. O 3 and NO 2 vertical profiles have been retrieved using a set of their air mass factors (AMFs) and SCDs measured over a range of 87-91.5 • SZA during the morning. The vertical profiles obtained by this method are compared with Umkehr profiles and ozonesondes and they are found to be in good agreement. The bulk of the column density is found near layer 20-25 km. Daily total column densities (TCDs) of O 3 and NO 2 along with their stratospheric and tropospheric counterparts are derived using their vertical profiles for the period 2000-2003. The total column, stratospheric column and tropospheric column amounts of both trace gases are found to be maximum in summer and minimum in the winter season. Increasing trend is found in column density of NO 2 in stratospheric, tropospheric and surface layers, but no trend is observed in O 3 columns for above layers during the period 2000-2003. Ground-based measurements include the Umkehr technique for measuring the profile of ozone concentration with the Dobson spectrophotometer at twilight (Gotz et al 1934) . The Umkehr technique provides ∼ 5 km vertical resolution for altitudes between 25 and 40 km along with low-resolution estimates above and below these altitudes. Ground based UV-visible spectrometer Keywords. Ozone; nitrogen dioxide; vertical profile; total column density; air mass factor; solar zenith angle.
doi:10.1007/bf02702046 fatcat:vq6zef3lvfachornj4j5eswjhy