Role of ozone in sun weather relationships

Abstract

This thesis comprises analytical studies of the relationships between solar/geomagnetic activity and the day-to-day variation of total atmospheric ozone at five selected stations — Resolute, Churchill, Hohenpeissenberg, Wallops Island, and New Delhi — during the period November 1975 to December 1979. Based on these studies, attempts have been made to look for evidence supporting certain possible mechanisms for sun–weather relationships.

A study of the photochemistry of ozone reveals that solar activity has both short-term as well as long-term influences on atmospheric ozone. To distinguish between these influences, a rank deviation technique has been developed. This technique separates the ozone data into two groups, which are then related to various indices of solar and geomagnetic activity.

Using the rank deviation technique, a study of the relationship between total atmospheric ozone and solar activity (by the indices of sunspot number and solar 10.7 MHz radio flux) reveals that a significant change in their relationship occurs between the sunspot minimum year (1976) and the sunspot maximum year (1979). This change, attributable to the more frequent occurrence of solar proton events in the sunspot maximum years, tends to indicate that solar cycle modulation is an unlikely mechanism for sun–weather relationships. An analysis of summer ozone data supports this general conclusion.

A winter analysis of the relationship between solar activity and total atmospheric ozone, however, reveals significant departures from the previous results. These departures are attributable to significant planetary wave activity in the winter stratosphere. A strong suggestion of an influence of solar activity on planetary wave activity is further supported by the observed relationship between solar activity and stratospheric warmings. These studies generally support the planetary wave mechanism for sun–weather relationships.