This study investigates the role that sea surface temperature (SST) variability plays in modulating the relationship between decadal-scale mean precipitation and monthly-scale extreme precipitation using the Australian Community Climate and Earth System Simulator Earth System model (ACCESS ESM1.5) climate model. The model large ensemble successfully reproduces the observed strong co-variability between monthly mean rainfall and wet extreme rainfall, defined as monthly rainfall totals above the 95th percentile. Removing SST variability in the ACCESS ESM1.5 model significantly weakens the co-variability between mean and wet extremes over most of the globe, showing that SSTs play a key role in modulating this co-variability. The study identifies Pacific and Atlantic SST patterns as the main drivers of the decadal scale co-variability in mean and extreme wet precipitation. On the other hand, observations and model results show that co-variability between mean and dry extremes is generally weaker than for wet extremes, with highly regional signals. Model experiments also show that SST variability plays a weaker role in modulating the co-variability between the mean precipitation and dry extremes as compared to wet extremes. These results suggest that stochastic atmospheric variability plays a stronger role in generating dry precipitation extremes compared SST forcing.

中文翻译：

---

海面温度驱动的平均和极端降水年代际协变性的调节

本研究利用澳大利亚共同体气候和地球系统模拟器地球系统模型（ACCESS ESM1.5）气候模型，研究了海面温度（SST）变化在调节十年尺度平均降水量和月尺度极端降水量之间的关系中所起的作用。 。该模型大型集合成功地再现了观察到的月平均降雨量和极端潮湿降雨量之间的强协变性，定义为月降雨量总量高于 95%。消除 ACCESS ESM1.5 模型中的海表温度变异性会显着削弱全球大部分地区的平均和潮湿极端值之间的协变性，表明海表温度在调节这种协变性方面发挥着关键作用。该研究确定太平洋和大西洋海温模式是平均和极端潮湿降水十年尺度协变性的主要驱动因素。另一方面，观测和模型结果表明，平均极端干旱天气之间的协变性通常弱于极端潮湿天气，具有高度区域性信号。模型实验还表明，与极端湿润天气相比，海温变异性在调节平均降水量与极端干旱之间的协变性方面的作用较弱。这些结果表明，与海温强迫相比，随机大气变率在产生极端干燥降水方面发挥着更强的作用。