ECHAM4

The ECHAM climate model was developed from the ECMWF atmospheric model and a comprehensive parameterisation package developed at Hamburg which allows the model to be used for climate simulations. The model is a spectral transform model with 19 atmospheric layers and the results used here derive from experiments performed with spatial resolution T42 (which approximates to about 2.8º longitude/latitude resolution). The model has also been used at resolutions in the range T21 to T106. ECHAM4 is the current generation in the line of ECHAM models (Roeckner, et al., 1992). A summary of developments regarding model physics in ECHAM4 and a description of the simulated climate obtained with the uncoupled ECHAM4 model is given in Roeckner et al. (1996). The ocean model is an updated version of the isopycnal model (OPYC3) developed by Josef Oberhuber (Oberhuber, 1993) at the Max-Planck-Institute for Meteorology, Hamburg, Germany.

The experiments from which results are used here consist of a climate change simulation in which historical greenhouse gas forcing from 1860 to 1990 is followed by a 1% per annum increase in radiative forcing (CO2 equivalent concentration) from 1990 to 2099. We acquired the results from this experiment from the IPCC Data Distribution Centre in 1999. The greenhouse gas only change fields used in SCENGEN are calculated as the difference in climate between the 30-year means of years 2071-2100 and 1961-90 in the greenhouse gas only forced simulation. The global warming by 2071-2100, with respect to 1961-90, was 3.0deg C and the increase in global precipitation was 1.97%, yielding a global precipitation sensitivity of 0.7% per degree Celsius warming. The climate sensitivity of the same atmospheric model, coupled to a mixed-layer ocean, was estimated to be 2.6deg C.

Several papers describe results using this version of the model - see Bacher et al. (1998), Oberhuber et al. (1998), Zhang et al. (1998).

Mean monthly precipitation pattern correlation coefficient = 0.74

References

Bacher,A., Oberhuber,J.M. and Roeckner,E. (1998) ENSO dynamics and seasonal cycle in the tropical Pacific as simulated by the ECHAM4/OPYC3 coupled general circulation model Climate Dynamics, 14, 431-450.

Oberhuber,J.M. (1993) Simulation of the Atlantic circulation with a coupled sea-ice mixed layer-isopycnal general circulation model. Part I: model description J. Phys. Oceanogr., 13, 808-829.

Oberhuber,J.M., Roeckner,E., Christoph,M., Esch,M. and Latif,M. (1998) Predicting the '97 El Niño event with a global climate model Geophys. Res. Letts., 25, 2273-2276.

Roeckner,E., Arpe,K., Bengtsson,L., Brinkop,S., Dümenil,L., Esch,M., Kirk,E., Lunkeit,F., Ponater,M., Rockel,B., Suasen,R., Schlese,U., Schubert,S. and Windelband,M. (1992) Simulation of the present-day climate with the ECHAM4 model: impact of model physics and resolution Max-Planck Institute for Meteorology, Report No.93, Hamburg, Germany, 171pp.

Roeckner,E., Arpe,K., Bengtsson,L., Christoph,M., Claussen,M., Dümenil,L., Esch,M., Giorgetta,M., Schlese,U. and Schulzweida,U. (1996) The atmospheric general circulation model ECHAM-4: model description and simulation of present-day climate Max-Planck Institute for Meteorology, Report No.218, Hamburg, Germany, 90pp.

Zhang,X-H., Oberhuber,J.M., Bacher,A. and Roeckner,E. (1998) Interpretation of interbasin exchange in an isopycnal ocean Climate Dynamics, 14, 725-740.