Vertical distribution of atmospheric ozone in low latitudes

Abstract

Observations of the light scattered from the clear blue zenith sky were made with Dobson’s photo-electric spectrophotometer at Delhi (28° 35′ N.) and Poona (18° 31′ N.) during the periods November 1945 to March 1947 and February–March 1948, and these have been used to determine the height distributions of atmospheric ozone at these places. After using Dobson’s method A in an exploratory way, the more detailed method B was used to calculate the vertical distributions from the observed Umkehr curves. Agreement between the observed and calculated points was obtained by trial and error at various zenith angles of the sun in the range 50°–90° where the effect of large particle scattering is negligible. Distributions of ozone are given for total ozone amounts varying from 0·155 cm. to 0·217 cm. at Delhi, the average heights of ozone for these being from 26·3 km. to 25·1 km. A decrease in the total ozone amount is found to cause a rise in the centre of gravity. At Poona, distributions for ozone amounts 0·164 cm. and 0·174 cm. give a more or less fixed height of 28·0 km. for the centre of gravity. The paper concludes with a brief survey of the distribution of ozone in the earth’s atmosphere both in the horizontal and the vertical and shows that it is easier to understand the regional, seasonal and day-to-day variations of ozone if we separately consider the contributions to total ozone content over any place from the photo-chemical action of sunlight and from transport in the horizontal and vertical directions of the accumulated ozone below the level of primary ozone formation.