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BMRC is now part of CAWCR: The Centre for Australian Weather and Climate Research.
For more information on The Centre please go to http://www.cawcr.gov.au
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The Land Surface and Climate Change: Uncertainties |
| Simulation of climate change is subject to many
uncertainties. One of these is due to the land surface.
As yet there is no “optimum” method of
incorporating the land surface into a climate model. In BMRC we are attempting to understand the uncertainties in climate projections for the Australian Region due to different assumptions about the land surface. We have run the BMRC climate model in “time-slice” (i.e. SST forced) mode for 1*CO2 and 2*CO2 using four different specifications of the water holding capacity of the land surface. (This was part of an experiment conducted under the experimental conditions of a European Union climate change initiative). |
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| Water Budget The surface water budget equation (1) is used as a method of checking conservation of water in the model. The straight lines indicate that water is conserved in the model. Equation (1) :- (1/R) * (dW/dt) ~ = 0 = (P/R) - (E/R) - 1
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| Comparison with Observations The surface air temperature averaged over all of Australia is plotted for each experiment and for each month of the year. The model is seen to be too warm compared to the observations (this has now been diagnosed as due to a too large amount of low cloud which has reduced the short wave radiation of the surface). The precipitation averaged over all of Australia is plotted for each experiment and for each month of the year. The model agrees with observations quite well. Seasonal variation in sensible heat fluxesin each model experiment.    |
| Experimental Results The differences in precipitation (2 * CO2 - 1 * CO2 ) is shown for each experiment (e.g. A2A1). The results indicate that, except possibly during the Austral summer, the change in precipitation forced by the change in CO2 is similar to the change due to the land surface. The differences in surface air temperature results indicate that the warming due to CO2 increases is much larger than any change due to the land surface; it is noteworthy that the actual CO2 induced change in temperature is quite sensitive to the specification of the land surface. |
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For more information, please contact:
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BMRC, Bureau of
Meteorology Research Centre
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| Experimental results described in these pages are from research systems developed in BMRC and are not part of the Bureau of Meteorology's operational products & services. |
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