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Regional climate models nested in global climate models are now being used in Aus- tralia to produce high resolution climate change scenarios for use in impact assessments. This paper describes the development of such scenarios for the State of Victoria in Southeastern Australia using the CSIRO Division of Atmospheric Research Limited Area Model (DARLAM) at a horizontal resolu- tion of 60 km nested in the slab ocean version of the CSIRO global climate model (GCM). Rainfall and temperature over Victoria are substantially better simulated in DARLAM than they are in the host GCM, although some poor features of the simulation of the seasonal cycle of rainfall have not been improved with the increase in resolution. There is evidence to suggest that some of these errors are due to errors in the simulation of atmospheric circulation provided by the host GCM. Under 2 × CO2 conditions, DARLAM simulates patterns of rainfall and temperature change which differ significantly from those provided by the host GCM and which appear more physically plausible. In particular, winter rainfall in southern Victoria increases in the DARLAM simulation, but decreases in the host GCM. Although the DARLAM scenario could be considered the best single scenario available for Victoria at the time of its production, it is noted that different, but equally plausible, scenarios could be obtained by nesting DARLAM in other GCMs, or by increasing the simulation sample size. Our assessment is that the rainfall changes simulated by DARLAM in summer may be most sensitive to such changes. In general, it is concluded that there is great potential to increase the realism of climate change scenarios in the Victorian region through careful use of nested regional modelling.

Atmospheric circulations, and related climate conditions, exert a strong influence on the transport and ultimate deposition of atmospheric pollutants. One potential outcome of climate change is alteration of atmospheric circulation patterns. The first stage in the development of a downscaling methodology to assess the influence of these possible future atmospheric circulation changes on trans- port and deposition of atmospheric pollutants over Europe is described. Firstly, the main modes of regional-scale circulation over a domain covering the North Atlantic and Europe are determined using principal components analysis of sea level pressure patterns. To determine whether the principal com- ponents represent circulation types found in reality, and show realistic relationships with surface temperature and precipitation amount, they are compared to the Lamb Weather Types, Central Eng- land Temperature, and England and Wales Rainfall. There are statistically significant relationships between some of the principal components and aqueous and ambient pollutant concentrations at 5 selected stations from the European Monitoring and Evaluation Programme monitoring network. Although, for any one combination of principal component and pollutant variable, the level of expla- nation can be quite small, notwithstanding some levels of variance explained for individual combina- tions being up to 69% (45% for the winter season, described in detail here). Because the pollution cli- mate at any one location is a function of many combinations of circulation/pollution relationships, despite the relatively small magnitude of variance explained for individual combinations in this study, the results confirm the utility of atmospheric circulation principal components in deriving downscaling relationships for surface pollution behaviour (via eventual multiple regressions, not reported in this paper), as well as giving further insight into the climatic influences on air and precipitation chemistry over Europe.