Abstract

MEENA, G. S.  and  JADHAV, D. B.. Study of diurnal and seasonal variation of atmospheric NO₂, O₃, H₂O and O₄ at Pune, India. Atmósfera [online]. 2007, vol.20, n.3, pp.271-287. ISSN 0187-6236.

Study of diurnal and seasonal variation of atmospheric trace gases is essential to understand our atmosphere. For this, daily zenith-sky scattered light observations have been made by UV-visible spectrometer during the period 2000-2003. Slant column densities (SCD) from morning (solar zenith angle SZA = 90º) to evening (SZA = 90º) were retrieved to see the diurnal variation of NO₂, O₃, H₂O and O₄. For the study of seasonal behavior of NO₂ and O₃, vertical column densities (VCD) were retrieved during the above period. For the whole period, NO₂ and O₃ VCD are found in a positive correlation of r = 0.72 for the morning data and r = 0.79 for the evening data. Satellites borne observations are compared with the spectroscopic observations, which are found in good correlation. It is seen that highest NO₂ and O₃ VCD are found in summer months (May and June) and lowest in winter months (December and January). Evening NO2 VCD are found higher compared to morning. There is found an interesting seasonal change that at Pune (18º32' N, 73º51' E), the evening-to-morning (PM/AM) ratios of NO₂ as well as temperature maximum/minimum ratios are higher in winter months and lower in summer months during the above period. In winter months NO₂ PM/AM ratio goes up to 3.8 and in summer months lowest ratio is 1.25. During the day, N₂O₅ can be photolyzed to regenerate NO₂, which reflects in the evening hours. In the winter, nights are longest; therefore, during night NO₂ to N₂O₅ conversion is more, hence in the morning NO₂ value will be less that leads to high PM/AM ratio. O₃ PM/AM ratio is slightly higher in winter months compared to summer months.

Keywords : Ozone; nitrogen dioxide; vertical column density; solar zenith angle; diurnal and seasonal variation.

        · abstract in Spanish     · text in English     · English ( pdf )