An interpretation of Australian rainfall projections

The majority of climate models project a winter rainfall reduction over south‐eastern Australia (SEA), while some show a tendency for a summer rainfall increase. The dynamics for these rainfall changes are not clear. Using outputs from a climate model, we show that a summer rainfall increase is consistent with a large Tasman Sea warming promoting convection, and an upward trend of the Southern Annular Mode (SAM) promoting onshore flows; these processes dominate over a rainfall decrease from an El Niño‐like warming pattern. In winter, similar effects from a Tasman Sea warming and an upward SAM trend operate along Australia's east coast, however, the rain‐reducing impact of an Indian Ocean Dipole‐like warming pattern dominates. In both seasons, the upward SAM trend causes a rainfall reduction over southern Australia. Summer rainfall over north‐western Australia is projected to decrease, due to an unrealistic relationship with the El Niño‐Southern Oscillation. Possible uncertainties are discussed.