The Barometer Coefficient and Air Mass Effects on Cosmic Rays at Macquarie Island

Abstract

The changes in cosmic ray intensity associated with the passage of weather fronts over the observing station have been investigated, using data from Macquarie Island. The effects can be explained in terms of the different way in which the height of the production layer for mesons varies with surface pressure for warm moist and cold dry air masses. The barometer coefficients found for these air masses are respectively ?0�120 � 0�058 per cent. per mb and ?0�220�0�041 per cent. per mb for the penetrating component. These results indicate that the frequently observed fluctuations in short-term barometer coefficients may be traceable to changes in air mass types.