Related to the Antarctic ozone depletion, south polar austral spring denotes the season of spring in the southern hemisphere when the greatest amount of ozone is lost, generally beginning in September. Astral relates to the hemisphere that the observer is currently in and the season that relates to the observer, while austral refers to the south.
[Glossary of Astronomy and Astrophysics; Hopkins, Jeanne; pg. 51; 1976; University of Chicago; Chicago.] [ Encyclopedia of Astronomy; Satterwaite, Gilbert; 29; 1971; St. Martins Press; NY.]
Source: Atmospheric Chemistry Glossary