Climate Dynamics ( IF 4.6 ) Pub Date : 2020-04-28 , DOI: 10.1007/s00382-020-05235-0 François P. D. Delage , Scott B. Power
The El Niño-Southern Oscillation (ENSO) drives substantial variability in precipitation and drought risk over Australia. Understanding the combined effect of anthropogenic forcing and ENSO on Australian precipitation extremes over the coming century can assist adaptation efforts. Here we use 24 CMIP5 climate models to examine externally forced changes in the frequency of “droughts”, when precipitation falls below the pre-industrial Decile 1 threshold. We focus on June to November (i.e., southern hemisphere Winter–Spring season) because precipitation during this period is important for agricultural production and recharging reservoirs in many parts of the country. The analysis in this paper is based on two 90-year simulations (1900–1989 and 2010–2099) for Historical and RCP8.5 scenarios. We show that the frequency of droughts, including droughts occurring in consecutive Winter–Spring seasons, is projected to increase in the twenty-first century under the RCP8.5 scenario in all eight Natural Resource Management (NRM) “clusters”. Approximately 60% of years are projected to be drought years in Perth, 35% in Adelaide, 30% in Melbourne, and approximately 20–25% of years in Sydney, Canberra and Brisbane. The relative frequency distributions of seasonally averaged Winter–Spring precipitation shift to lower values in all NRM clusters. However, apart from the Southern and Southwestern Flatlands, the shifts are accompanied by changes in the shape of the distributions whereby the high end of the distributions do not shift as much as other parts of the distribution and the wettest seasons become marginally wetter. This means that in most locations generally drier conditions are projected to be infrequently punctuated by seasons that are just as wet or wetter than the wettest years experienced during the twentieth century. While the models generally do a poor job in simulating ENSO precipitation teleconnections over Australia, an increase in ENSO-driven variability is suggested for the Wet Tropics, the Monsoonal North, the Central Slopes and the Southern and Southwestern Flatlands.
中文翻译:
全球变暖和厄尔尼诺-南方涛动对澳大利亚季节性极端降水的影响
厄尔尼诺-南方涛动(ENSO)导致澳大利亚降水和干旱风险的巨大差异。了解人为强迫和ENSO对即将来临的澳大利亚极端降水的综合影响可以帮助适应工作。在这里,我们使用24个CMIP5气候模式来检验当降水量降到工业化前十进制1阈值以下时,外部干旱在“干旱”频率上的变化。我们集中在6月至11月(即南半球冬春季节),因为这段时期的降水对于该国许多地区的农业生产和蓄水库很重要。本文的分析基于对历史和RCP8.5场景的两个90年模拟(1900–1989和2010–2099)。我们证明干旱的频率,在RCP8.5情景下,所有八个自然资源管理(NRM)“集群”中,包括连续冬冬季出现的干旱在内的二十一世纪,预计都会增加。珀斯预计约有60%的干旱年份,阿德莱德约为35%,墨尔本为30%,悉尼,堪培拉和布里斯班约为20-25%。在所有NRM聚类中,季节性平均冬春季降水的相对频率分布都向较低的值转移。但是,除了南部和西南平原地区,这些变化还伴随着分布形状的变化,从而分布的高端变化不如分布的其他部分那么多,最湿的季节变得略微湿润。这意味着,在大多数地区,预计较干燥的环境很少会出现与20世纪最湿润的季节一样潮湿或潮湿的季节。虽然这些模型在模拟澳大利亚全国ENSO降水遥相关方面通常做得很差,但建议对热带地区,季风北部,中部斜坡以及南部和西南平原的ENSO驱动的变异性增加。