A GCM study on the maintenance of the June 1982 blocking in the Southern Hemisphere

GCM experiments are used to study several possible mechanisms associated with the maintenance of the June 1982 blocking in the Southern Hemisphere. The mechanisms considered include changed orography, sea surface temperature anomalies, tropical heating, regional heating in the Pacific area, land-sea contrast, and sensible heating in the Antarctic area. It is concluded that asymmetric heating due to land-sea contrast was the most important boundary forcing associated with maintenance of the block. A 'no Australia' experiment confirms this result and suggests that local land-sea contrast kept the block stationary. High-latitude sensible heating associated with cold air outbreaks from Antarctica was also important in maintaining the block.