long-distance climatic teleconnection pattems(e.g. the influence of Asian aerosols on land-sea temperature gradients which may affect the Australian monsoon) Simplifications in the representation of ocean processes are likely to be important in determining pattems of climate change in the Australian region, such as changes in the vertical profile of ocean temperature/salinity and the El Nino-Southern Oscillation. The climatic influence of small-scale features such as tropical cyclones and stoms cannot be resolved at this stage Plant physiology is not included, so simulated vegetation does not respond to climate change or increased levels of COz. However, significant bios pheric responses to climate change could occur in the real world, as could changes in land-use, with consequent climatic feedbacks CSIRO Mark 2 global climate model with slab ocean(CSIRO slab) The CSIRO Mark 2 GCM is aspectual model with R21 horizontal resolution grid boxes measuring about 625 km by 350 km) and has 9 vertical levels in the atmosphere(Watterson et al., 1997). This gives 41 grid boxes over Australia. Global atmospheric and biospheric sub-models are coupled to a slab ocean sub-model Simplifications of physical processes such as convection, radiation, gravity wave drag, cloud formation sea- ice formation and biospheric interactions are detailed in Mc gregor et al. (1993), Mc Gregor(1993 Kowalczyk et al. (1994)and O'Farrell ( 1998) Adjusted heat fluxes are applied to the slab ocean to represent heat from the deep ocean and the effect of currents(Watterson et al., 1997). Fluxes are determined from a separate 10-year experiment driven by observed sea-surface temperatures(SSTs). Regional flux adjustments are required to keep simulated sea-surf ace temperatures close to those observed, and these monthly average flux adjustments were saved for use in 1x CO2 and 2x COz experiments. Whenflux adjustments are applied in the 1x CO2 run, the simulated SSTs and other continental-scale climatic features are similar to those observed. The same flux adjustments are applied in the 2x CO2 run, which places an artificial constraint on the variability of sea-surf ace temperature as the climate changes. This limitation may have important implications for projected ocean behaviour and atmospheric circulation patterms. On a CRAY Y-MP computer, climate variables for one model day take 30 seconds to evaluate, so a 10 year run takes 50 hours CSIRO regional climate model (DARLAN) Over the Australasian region(71E-177E, 12N-57S), the CSIRO regional climate model (DARLAM)has been driven at its lateral boundaries by output from the CSIRO Mark 2 GCM(Walsh and Mc Gregor, 1995; McGregor et al., submitted). DARLAM has nine vertical levels in the atmo sphere and grid boxes measuring about 125 km by 125 km, giving 442 grid boxes over Australia
long-distance climatic teleconnection patterns (e.g. the influence of Asian aerosols on land -sea temperature gradients which may affect the Australian monsoon). Simplifications in the representation of ocean processes are likely to be important in determining patterns of climate change in the Australian region, such as changes in the vertical profile of ocean temperature/salinity and the El Niño -Southern Oscillation. The climatic influence of small-scale features such as tropical cyclones and storms cannot be resolved at this stage. Plant physiology is not included, so simulated vegetation does not respond to climate change or increased levels of CO2. However, significant biospheric responses to climate change could occur in the real world, as could changes in land-use, with consequent climatic feedbacks. CSIRO Mark 2 global climate model with slab ocean (CSIRO slab) The CSIRO Mark 2 GCM is a spectral model with R21 horizontal resolution (grid boxes measuring about 625 km by 350 km) and has 9 vertical levels in the atmosphere (Watterson et al., 1997). This gives 41 grid boxes over Australia. Global atmospheric and biospheric sub-models are coupled to a slab ocean sub-model. Simplifications of physical processes such as convection, radiation, gravity wave drag, cloud formation, sea-ice formation and biospheric interactions are detailed in McGregor et al. (1993), McGregor (1993), Kowalczyk et al. (1994) and O’Farrell (1998). Adjusted heat fluxes are applied to the slab ocean to represent heat from the deep ocean and the effect of currents (Watterson et al., 1997). Fluxes are determined from a separate 10-year experiment driven by observed sea-surface temperatures (SSTs). Regional flux adjustments are required to keep simulated sea-surface temperatures close to those observed, and these monthly average flux adjustments were saved for use in 1×CO2 and 2×CO2 experiments. When flux adjustments are applied in the 1×CO2 run, the simulated SSTs and other continental-scale climatic features are similar to those observed. The same flux adjustments are applied in the 2×CO2 run, which places an artificial constraint on the variability of sea-surface temperature as the climate changes. This limitation may have important implications for projected ocean behaviour and atmospheric circulation patterns. On a CRAY Y-MP computer, climate variables for one model day take 30 seconds to evaluate, so a 10 year run takes 50 hours. CSIRO regional climate model (DARLAM) Over the Australasian region (71°E–177°E, 12°N–57°S), the CSIRO regional climate model (DARLAM) has been driven at its lateral boundaries by output from the CSIRO Mark 2 GCM (Walsh and McGregor, 1995; McGregor et al., submitted). DARLAM has nine vertical levels in the atmosphere and grid boxes measuring about 125 km by 125 km, giving 442 grid boxes over Australia
The atmospheric sub-model interacts with a slab ocean sub-model and uses descriptions of physical processes which are similar to those in the csIRo Mark 2 GCM. Ho wever, DARLAM uses a modified convection scheme, a different soil moisture scheme and excludes gravity wave drag. Sensitivity experiments showed that results were not greatly affected by the change in convection scheme On a CRAY Y-MP computer, climate variables for one model day take 130 seconds to evaluate, so a 10 year run takes 132 hours CSIRo global coupled ocean-atmosphere-sea-ice model(CSIRO coupled) The CSIRo coupled model involves global atmospheric, oceanic, sea- ice and biospheric sub-models (Gordon and OFarrell, 1997; Hirst et al., 1997). The atmospheric, biospheric and sea-ice sub-models are the same as those used in the cSIRo Mark 2 GCM. Atmospheric and oceanic components use a spectral R21 horizontal grid(each gridbox measuring about 625 km by 350 km)with 9 vertical levels in the atmosphere and 21 levels in the ocean. The ocean model has a heat trans port scheme whi ch significantly reduces problems associated with excessive mixing in the Southem Ocean. On a CRAY Y-MP computer, climate variables for one model day take 60 seconds to evaluate, so a 10 year run takes 61 hours Coupling the atmosphere to the ocean is technically challenging because the ocean has a much longer timescale of variability than the atmosphere. The coupled model requires adjustments to the fluxes of heat salinity and wind stress which link the atmospheric and oceanic components. Adjusting the heat fluxes at the ocean/atmosphere/ice interface is performed by running the ocean and atmosphere models independently and computing()the fluxes required by the ocean model when driven by observed SST, sea-surf ace surface salinity(sSS)and wind stress, and (i) the heat fluxes generated by the atmosphere/ice model with observed SST and SSS. The flux adjustment is the difference between() and(i). These adjustments were used in the fully coupled model which generates its own SST, SSS and wind stress The same flux adjustments are applied to the transient CO2 run Hirst et al., 1997), which places an artificial constraint on the variability of sea-surface temperature as the climate changes. Flux adjustments in the coupled experiment are much smaller than the Q- fluxes in the csIRO slab experiment. Experiments conducted This section describes three CSIRO enhanced greenhouse experiments. Provision of output from these experiments is intended to give users an intemally consistent set of detailed climatic variables for use in sensitivity studies. Those wishing to undertake impact assessments or sens itivity studies which incorporate a wider range of future climates should use the simplified scenarios of csiRo (1996)which are based on consensus results of five intemational global climate models
The atmospheric sub-model interacts with a slab ocean sub-model and uses descriptions of physical processes which are similar to those in the CSIRO Mark 2 GCM. However, DARLAM uses a modified convection scheme, a different soil moisture scheme and excludes gravity wave drag. Sensitivity experiments showed that results were not greatly affected by the change in convection scheme. On a CRAY Y-MP computer, climate variables for one model day take 130 seconds to evaluate, so a 10 year run takes 132 hours. CSIRO global coupled ocean-atmosphere-sea-ice model (CSIRO coupled) The CSIRO coupled model involves global atmospheric, oceanic, sea-ice and biospheric sub-models (Gordon and O'Farrell, 1997; Hirst et al., 1997). The atmospheric, biospheric and sea-ice sub-models are the same as those used in the CSIRO Mark 2 GCM. Atmospheric and oceanic components use a spectral R21 horizontal grid (each gridbox measuring about 625 km by 350 km) with 9 vertical levels in the atmosphere and 21 levels in the ocean. The ocean model has a heat transport scheme which significantly reduces problems associated with excessive mixing in the Southern Ocean. On a CRAY Y-MP computer, climate variables for one model day take 60 seconds to evaluate, so a 10 year run takes 61 hours. Coupling the atmosphere to the ocean is technically challenging because the ocean has a much longer timescale of variability than the atmosphere. The coupled model requires adjustments to the fluxes of heat, salinity and wind stress which link the atmospheric and oceanic components. Adjusting the heat fluxes at the ocean/atmosphere/ice interface is performed by running the ocean and atmosphere models independently and computing (i) the fluxes required by the ocean model when driven by observed SST, sea-surface surface salinity (SSS) and wind stress, and (ii) the heat fluxes generated by the atmosphere/ice model with observed SST and SSS. The flux adjustment is the difference between (i) and (ii). These adjustments were used in the fully coupled model which generates its own SST, SSS and wind stress. The same flux adjustments are applied to the transient CO2 run (Hirst et al., 1997), which places an artificial constraint on the variability of sea-surface temperature as the climate changes. Flux adjustments in the coupled experiment are much smaller than the Q-fluxes in the CSIRO slab experiment. Experiments conducted This section describes three CSIRO enhanced greenhouse experiments. Provision of output from these experiments is intended to give users an internally consistent set of detailed climatic variables for use in sensitivity studies. Those wishing to undertake impact assessments or sensitivity studies which incorporate a wider range of future climates should use the simplified scenarios of CSIRO (1996) which are based on consensus results of five international global climate models