HR: 08:30h
AN: GC11A-03    [Abstracts]
TI: Australian Climate and its Potential Changes Simulated by IPCC AR4 Coupled GCMs
AU: * Moise, A F
EM: a.moise@bom.gov.au
AF: Bureau of Meteorology Research Centre, PO Box 1289, Melbourne, VIC 3054 Australia
AB: The purpose of this paper is to present an evaluation of 14 recently submitted coupled model simulations for the fourth IPCC scientific assessment. The analysis is focused on the Australian region. Monthly rainfall and surface air temperature climatologies over the Australian region have been derived from the IPCC-CMIP 20th century simulations and compared with observations from the Australian Bureau of Meteorology. The gross spatial patterns of austral summer rainfall (DJF) are reasonably simulated by the majority of the models. However, there are significant model errors in simulating the intensity and location of the heavy Australian monsoon rainfall in the north and eastern parts of the continents, with more than half of the models showing a substantial underestimation of the rainfall climatology across tropical Australia leading to a negative bias in the ensemble mean model of around 40 mm/month. A number of models are simulating wrong locations of the monsoon rainfall. The seasonal cycle of the surface temperature is also quite reasonably reproduced in the models although there are biases of around 2°C present in the model simulated surface air temperature climatology. Based on the 100-year model simulations of future climate change, with varying yearly increase of atmospheric greenhouse gas concentrations for three different emission scenarios B1, A1B and A2, the changes of surface air temperature and precipitation have also been analyzed. The average surface temperature change in the last 20-year period of the three climate change simulations (yrs 2081-2100) against the model 20th century simulations (yrs 1981-2000) over the entire Australian continent is 1.7 ± 0.1 °C (B1), 2.8 ± 0.2 °C (A1B), and 3.5 ± 0.3 °C (A2) for the model ensemble mean. The temperature range covered by the suit of model simulations within each scenario is 0.8°C, 1.7°C, and 1.2°C respectively. Results for three Australian subregions will also be discussed. The spatial distribution of the model-simulated surface temperature and precipitation changes have been analyzed. Surface temperature is warmed over the whole continent in all models, while the changes in precipitation show large spatial variations, with some models simulating more than 20mm/month increase while others show more than 8 mm/month decrease. Among the model simulations under different emission scenarios, there is a consistent signal of decreased rainfall over most southern parts of Australia, especially South-West Western Australia.
DE: 1600 GLOBAL CHANGE
DE: 1626 Global climate models (3337, 4928)
DE: 1630 Impacts of global change (1225)
DE: 1637 Regional climate change
SC: Global Climate Change [GC]
MN: Fall Meeting 2005