Simulated changes in daily rainfall intensity due to the enhanced greenhouse effect: Implications for extreme rainfall events
- CSIRO Division of Atmospheric Research, Victoria (Australia); and others
This study presents rainfall results from equilibrium 1x- and 2xCO{sub 2} experiments with the CSIRO 4-level general circulation model. The 1xCO{sub 2} results are discussed in relation to observed climate. Discussion of the 2xCO{sub 2} results focuses upon changes in convective and non-convective rainfall as simulated in the model, and the consequences these changes have for simulated daily rainfall intensity and the frequency of heavy rainfall events. The significant shortcomings of GCM simulations of precipitation processes are recognized. Generally, the model results show a marked increase in rainfall originating from penetrative convection and, in the mid-latitudes, a decline in large-scale (non-convective) rainfall. It is argued these changes in rainfall type are a consequence of the increased moisture holding capacity of the warmer atmosphere simulated for 2xCO{sub 2} conditions. Related to changes in rainfall type, rainfall intensity (rain per rain day) increases in the model for most global regions. Increases extend even to regions where total rainfall decreases. Indeed, the greater intensity of daily rainfall is a much clearer response of the model to increased greenhouse gases than the changes in total rainfall. We also find a decrease in the number of rainy days in the middle latitudes of both the Northern and Southern Hemispheres. To further elucidate these results daily rainfall frequency distributions are examined globally and four selected regions of interest. In all regions the frequency of high rainfall events increases, and the return period of such events decreases markedly. If realistic, the findings have potentially serious practical implications in terms of an increased frequency and severity of floods in most regions. However, we discuss various important sources of uncertainty in the results presented, and indicate the need for rainfall intensity results to be examined in enhanced greenhouse experiments with other GCMs. 31 refs., 20 figs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 181902
- Journal Information:
- Climate Dynamics, Vol. 8, Issue 1; Other Information: PBD: Oct 1992
- Country of Publication:
- United States
- Language:
- English
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