Australia and the Pacific

Australian and Pacific climates are the product of the moderating influence and atmospheric pressure features of the world’s largest ocean. The atmospheric circulation is controlled by the Hawaiian-Pacific High, the South Indian Ocean High, and the South Pacific High. The associated tropical trade winds converge on the inter-tropical convergence zone (ITCZ), oscillating northward and southward with the seasons. Converging winds from anticyclones situated over Australia with those from the South Pacific High create the South Pacific convergence zone (SPCZ). Ocean currents, particularly the West Australian and Leeuwin Currents, bring moderating and also varying conditions to mainland Australia. Temperatures are tropical to subtropical over nearly all of the region, with excessively high temperatures in the arid Australian Outback. Coastal Australia has moderate temperatures and abundant precipitation. New Zealand has topography and a position that allows for relatively abundant precipitation and moderate temperatures. Both the ITCZ and SPCZ create precipitation for much of the Pacific islands, but variability in their position, especially for the SPCZ and associated with El Niño-Southern Oscillation (ENSO) and the Quasi-biennial Oscillation (QBO), makes precipitation inconsistent. Inhabitability of the islands is directly related to consistency of water availability.