The role of topography on projected rainfall change in mid-latitude mountain regions
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Change to precipitation in a warming climate holds many implications for water management into the future, and an enhancement of a precipitation decrease or increase on or around mountains would have numerous impacts. Here, an intermediate resolution regional climate model (RCM) ensemble projects enhanced precipitation decrease on the windward slopes of over many mid-latitude mountains in winter, consistent with theory and model studies of idealised mountain ranges. This ensemble projects that an increase in convective rainfall determines the sign of total rainfall change in many regions in summer, only some of which are on or near mountains such as the European Alps. These same projected changes are present in inland slopes of the Australian Alps compared to surrounding regions as simulated by three RCM ensembles (the intermediate resolution and two high resolution ensembles), which agree on an enhanced precipitation decrease on the windward slopes in winter and spring, as well as an enhanced precipitation increase in summer driven by an increase in convective rainfall. The ensembles disagree on an enhanced precipitation decrease in autumn. The results represent regional-scale added value in the climate change signal of projections from high resolution models in cooler seasons, but suggest that the specific model components such as convection schemes strongly influence projections of summer rainfall change. Confidence in the simulation of change in convective rainfall, or convection-permitting modelling may be needed to raise confidence in summer rainfall projections over mountains.
KeywordsRegional climate models Added value Rainfall Climate change
This work was supported by the Australian Government’s National Environmental Science Program’s Earth System and Climate Change hub, the Victorian Government’s Department of Environment Land Water and Planning climate projections 2019 project (VCP19), Queensland Climate Adaptation Strategy (Q-CAS) and the Wine Australia Institute climate project. We thank John McGregor and Jack Katzfey from CSIRO for additional modelling support, helpful advice and assistance.
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