An understanding of past hydroclimatic variability is critical to resolving the significance of recent recorded trends in Australian precipitation and informing climate models. Our aim was to reconstruct past hydroclimatic variability in semi-arid northwest Australia to provide a longer context within which to examine a recent period of unusually high summer-autumn precipitation. We developed a 210-year ring-width chronology from Callitris columellaris, which was highly correlated with summer-autumn (Dec–May) precipitation (r = 0.81; 1910–2011; p < 0.0001) and autumn (Mar–May) self-calibrating Palmer drought severity index (scPDSI, r = 0.73; 1910–2011; p < 0.0001) across semi-arid northwest Australia. A linear regression model was used to reconstruct precipitation and explained 66% of the variance in observed summer-autumn precipitation. Our reconstruction reveals inter-annual to multi-decadal scale variation in hydroclimate of the region during the last 210 years, typically showing periods of below average precipitation extending from one to three decades and periods of above average precipitation, which were often less than a decade. Our results demonstrate that the last two decades (1995–2012) have been unusually wet (average summer-autumn precipitation of 310 mm) compared to the previous two centuries (average summer-autumn precipitation of 229 mm), coinciding with both an anomalously high frequency and intensity of tropical cyclones in northwest Australia and the dominance of the positive phase of the Southern Annular Mode.
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机译:了解过去的水文气候变异性对于解决澳大利亚降水最近记录的趋势和告知气候模式的重要性至关重要。我们的目的是在澳大利亚西北半干旱地区重建过去的水文气候变异性,以提供更长的时间范围,以研究近期异常高的夏季-秋季降水。我们从Callitris columellaris开发了210年的环宽年表,这与夏秋季(12月至5月)的降水(r = 0.81; 1910-2011; p <0.0001)和秋季(3月至5月)的自相关高度相关。在澳大利亚西北半干旱地区校准帕尔默干旱严重度指数(scPDSI,r = 0.73; 1910-2011; p <0.0001)。线性回归模型用于重建降水,并解释了观测到的夏秋季降水的66%的方差。我们的重建揭示了过去210年间该地区水气候的年际至数十年尺度变化,通常显示降水低于平均水平的时期为一到三十年,降水高于平均水平的时期通常少于十年。我们的结果表明,与前两个世纪(夏秋季平均降水量为229 mm)相比,最近二十年(1995-2012)异常潮湿(夏季秋季平均降水量为310 mm),这两者都异常高澳大利亚西北部热带气旋的频率和强度,以及南部环形模式正相的优势。
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