Effect of Solar Activity on Atmospheric Ozone

Abstract

THE ozone layer in the atmosphere constitutes a physical link of considerable importance between the upper atmosphere on one hand, and the lower atmosphere on the other. The former is known to respond directly to variations in the ultra-violet and corpuscular radiation from the Sun as evidenced by ionospheric and geomagnetic variations. On the other hand, the response of terrestrial weather and climate to solar activity has not been established with any degree of certainty; indeed, many of the solar-weather relationships investigated from time to time have remained controversial. The possible effect of solar activity on the ozone layer itself is thus of considerable importance in the context of the general problem of solar-terrestrial relationships. Ever since systematic measurements of total ozone by the Dobson spectro-photometer commenced, numerous attempts have been made to seek a relation between long-period variations in total ozone and solar activity, but the results obtained so far have been inconclusive. Among recent investigations on this problem may be mentioned that of Willet¹, who after a study of world-wide ozone for a period of about 27 years came to the conclusion that there is a significant negative correlation between world-wide monthly average of total ozone and the monthly mean sunspot number. Mitchell² has, however, reviewed Willet's statistical results and expressed doubts about the significance of the results. London and Haurwitz³ have also re-examined Willet's data and method of analysis and have shown that the correlations have no significance. The behaviour of total ozone in response to geomagnetic activity at individual stations has been examined by Ahmed and Halim⁴, who did not find any significant correlation. Kulkarni⁵, however, after studying the meridional gradient of total ozone during severe magnetic storms, has shown that in association with such storms the total ozone in high latitudes tends to decrease and that in middle latitudes it tends to increase. All this work refers to the total ozone. The relationship between solar activity and the fractional amount of ozone that is in photochemical equilibrium in the upper stratosphere appears not to have been examined.