Periods of water surplus and deficit in Northern California follow a pronounced quasi-decadal cycle. This cycle is largely driven by the frequency of atmospheric rivers (ARs), affecting the region’s wet and dry periods. Our analyses demonstrate that the quasi-decadal cycle of AR frequency relies on moisture transport associated with the position and intensity of the Aleutian Low. In observations, the Aleutian Low is shown to covary with tropical Pacific sea surface temperature anomalies. A modeling experiment, which incorporates ocean observations from the equatorial Pacific into the fully coupled climate model, provides support that the quasi-decadal cycle of the Aleutian Low is forced by the tropical Pacific. Subsequently, the tropical Pacific modulates the wet season moisture transport toward California on decadal time scales, affecting AR frequency. These results provide metrics for improving interannual-to-decadal prediction of AR activity, which drives hydrological cycles in Northern California.

中文翻译：

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影响北加州的大气河流表现出准年代际频率

北加利福尼亚州的水资源过剩和短缺时期遵循明显的准十年周期。这个循环主要由大气河流 (AR) 的频率驱动，影响该地区的干湿期。我们的分析表明，AR 频率的准年代际循环依赖于与阿留申低压的位置和强度相关的水分输送。在观测中，阿留申低压显示出与热带太平洋海面温度异常共变。一项模拟实验将赤道太平洋的海洋观测纳入完全耦合的气候模型，支持阿留申低压的准年代际周期受热带太平洋强迫。随后，热带太平洋在十年时间尺度上调节了向加利福尼亚的湿季水分输送，影响 AR 频率。这些结果为改进 AR 活动的年际到年代际预测提供了指标，该活动推动了北加州的水文循环。