Daily Variation of Amount of Ozone in the Atmosphere

Abstract

THE improved form of Dobson's spectrophotometer using an RCA 1P28 photo-multiplier tube enables measurements of atmospheric ozone to be made with the light from the moon. Dobson's own measurements¹ made at Oxford during November–December, 1948, showed variations of ozone on some nights, and he concluded that they could be attributed to changes in meteorological conditions. As the day-to-day variations of amount of ozone in middle latitudes are large, it would be difficult to find without prolonged observation whether there is any systematic difference between the ozone amounts during day- and night-hours. In low latitudes, however, both the total amount as well as the day-to-day variations are small during a large part of the year, and if a regular daily variation exists as might be expected from the photochemical theory of atmospheric ozone, it could be determined from a short series of observations. Accordingly, observations were made at Mount Abu and Ahmedabad in the period November 1952–April 1953, and these show clearly that there is a substantial increase of ozone during night-hours, as compared to day-hours.