Synoptic aspects of wet and dry conditions in central Australia: Observations and GCM simulations for 1 {times} CO{sub 2} and 2 {times} CO{sub 2} conditions
- CSIRO Division of Atmospheric Research, Victoria (Australia)
Synoptic climatological patterns that produce anomalous wet conditions in central Australia during the period form September to April have been studied. The analysis was done by using observed daily rainfall data at a number of stations, wind and mean sea level pressure from the European Centre for Medium Range Weather Forecasts (ECMWF), Tropical Ocean and Global Atmosphere (TOGA) data form 1985 to 1991, and the CSIRO 9-level (CSIRO9) global climate model (GCM) simulated data for 1 {times} CO{sub 2} and 2 {times} CO{sub 2} experiments. For rainfall values above 99.5 percentile in observed and simulated data, wet days have been selected to study the synoptic-scale weather systems that produce anomalous wet events in central Australia. As the vast majority of days in central Australia are dry, the same number of days with no rainfall for both observed and simulated conditions have been selected randomly. A comparison between CSIRO9 simulated synoptic patterns and observed synoptic patterns reveals that the model fairly well captures the synoptic climatological characteristics which produce anomalous wet and contrasting dry weather conditions during the period from September to April. Under enhanced greenhouse experiments, the main features of the synoptic patterns are intensified both for wet and dry conditions, which result in an increase in extreme-weather conditions, an increase in rainfall intensity, a spatial expansion of the heavy rainfall region during wet days, and an expansion of the dry area during dry days. During anomalous wet conditions, the low pressure area is intensified, monsoonal winds and southeasterlies are strengthened and strong wind shear over tropical Australia is simulated. During this condition, the monsoon shear line moves poleward particularly over the Northern Territory. In contrast, during dry conditions, the anticyclonic circulation over the continent is strengthened.
- OSTI ID:
- 456813
- Journal Information:
- Climate Dynamics, Vol. 10, Issue 8; Other Information: PBD: Nov 1994
- Country of Publication:
- United States
- Language:
- English
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