W. M. Connolley and J. C. King
British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK
Email: wmc@bas.ac.uk
Using a hierarchy of climate models together with observations from gridded analyses, we examine the atmosphere-only and coupled ocean-atmosphere variability in the general circulation for the region south of 40 øS. Model data are taken from a hierarchy of runs of the Hadley Centre GCM, HADAM2 and HADCM2. Observational data come from the Australian Bureau of Meteorology analyses and the NCEP/NCAR reanalyses. The variability in mean sea level pressure (MSLP) is well simulated by the coupled models. A complication is that the difference between the analyses used for verification is comparable to the analysis-model differences. The model without interannual variations in sea surface temperatures (SSTs) simulates the major observed features of variability, but an increase in variability and fidelity to the observations is seen within the hierarchy of model runs. The temporal variation in MSLP in southern high latitudes has a white spectrum consistent with "random" forcing by weather events and a decoupling from oceanic "integration". In contrast, the spatial pattern of MSLP variability shows large-scale structure that is consistent between observations and various models, even without interannual variation in SSTs. This shows that the models are sufficiently skilful to reproduce the pattern of observed variability and suggests that the pattern of variability is a characteristic of the land-sea distribution and topography.