Abstract
Abstract. In this paper regional (synoptic) and large-scale climate drivers of rainfall are investigated for Victoria, Australia. A non-linear classification methodology known as self-organizing maps (SOM) is used to identify 20 key regional synoptic patterns, which are shown to capture a range of significant synoptic features known to influence the climate of the region. Rainfall distributions are assigned to each of the 20 patterns for nine rainfall stations located across Victoria, resulting in a clear distinction between wet and dry synoptic types at each station. The influence of large-scale climate modes on the frequency and timing of the regional synoptic patterns is also investigated. This analysis revealed that phase changes in the El Niño Southern Oscillation (ENSO), the Indian Ocean Dipole (IOD) and/or the Southern Annular Mode (SAM) are associated with a shift in the relative frequency of wet and dry synoptic types on an annual to inter-annual timescale. In addition, the relative frequency of synoptic types is shown to vary on a multi-decadal timescale, associated with changes in the Inter-decadal Pacific Oscillation (IPO). Importantly, these results highlight the potential to utilise the link between the regional synoptic patterns derived in this study and large-scale climate modes to improve rainfall forecasting for Victoria, both in the short- (i.e. seasonal) and long-term (i.e. decadal/multi-decadal scale). In addition, the regional and large-scale climate drivers identified in this study provide a benchmark by which the performance of Global Climate Models (GCMs) may be assessed.
Highlights
Managing a highly variable climate alongside increasing demand for natural resources represents one of the most significant challenges for sustainable water resources management in many parts of the world
This paper aims to identify the key regional synoptic patterns that are related to rainfall variability in Victoria and to determine how the regional patterns are modulated by the large-scale climate modes
It is clear that Pacific, Indian and Southern Ocean climate variability plays an important role in modulating the regional synoptic systems that deliver rainfall to Victoria
Summary
Managing a highly variable climate alongside increasing demand for natural resources represents one of the most significant challenges for sustainable water resources management in many parts of the world. The IPO/PDO has been found to be a dominant climate mode in the Pacific sector since at least the 15th Century (Verdon and Franks, 2006) and is likely to continue to influence climate in the future It appears that during the mid-1990’s southeastern Australia, in particular Victoria, experienced a step change towards a drier climate, resulting in lower than average rainfall and streamflows over the past decade, placing. This paper aims to identify the key regional synoptic patterns that are related to rainfall variability in Victoria and to determine how the regional patterns are modulated by the large-scale climate modes (including IPO, ENSO, IOD and SAM). The link between these synoptic patterns and Victorian rainfall is assessed, followed by an analysis of the relationship between large-scale climate phenomena and the frequency of occurrence of the key regional synoptic patterns
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