Understanding how drivers of climate change affect precipitation remains an important area of research. Although several robust precipitation responses have been identified under continued increases in greenhouse gases (GHGs), considerable uncertainty remains. This is particularly the case at regional scales, including the West Coast of the United States and California. Here, we exploit idealized, single forcing simulations from the Precipitation Driver Response Model Intercomparison Project (PDRMIP) to address how climate drivers impact California wintertime precipitation. Consistent with recent work, GHGs including carbon dioxide and methane, as well as solar forcing, yield a robust increase in California wintertime precipitation. We also find robust California precipitation responses to aerosols but with opposite responses for sulfate versus black carbon aerosol. Sulfate aerosol increases California wintertime precipitation, whereas black carbon reduces it. Moreover, California precipitation is more sensitive to aerosols, particularly regional emissions from Europe and Asia, than to GHGs. These precipitation responses are consistent with shifts in the jet stream and altered moisture fluxes. Although the idealized nature of PDRMIP simulations precludes a formal attribution, our results suggest that aerosols can perturb precipitation and fresh water resources along the West Coast of the United States.

中文翻译：

---

评估加利福尼亚对各种气候驱动因素的冬季降水响应

了解气候变化的驱动因素如何影响降水仍然是重要的研究领域。尽管在温室气体（GHGs）持续增加的情况下已经确定了几种强有力的降水响应，但是仍然存在很大的不确定性。在区域规模上尤其如此，包括美国的西海岸和加利福尼亚。在这里，我们利用降水驱动程序响应模型比较项目（PDRMIP）的理想化的单强迫模拟来解决气候驱动程序如何影响加利福尼亚州冬季降水的问题。与最近的工作一致，包括二氧化碳和甲烷在内的温室气体以及太阳强迫，使加利福尼亚州的冬季降水大幅增加。我们还发现加利福尼亚州对气溶胶的降水响应很强，但硫酸盐和黑碳气溶胶的响应却相反。硫酸盐气溶胶会增加加利福尼亚州冬季的降水量，而黑碳会减少它。此外，加州的降水对气溶胶，特别是欧洲和亚洲的区域排放，比对温室气体更为敏感。这些降水响应与射流的变化和湿气通量的变化是一致的。尽管PDRMIP模拟的理想性质无法正式归因，但我们的结果表明，气溶胶会扰乱美国西海岸的降水和淡水资源。加利福尼亚州的降水对气溶胶，特别是欧洲和亚洲的区域排放，比对温室气体更为敏感。这些降水响应与射流的变化和湿气通量的变化是一致的。尽管PDRMIP模拟的理想性质无法正式归因，但我们的结果表明，气溶胶会扰乱美国西海岸的降水和淡水资源。加利福尼亚州的降水对气溶胶，特别是欧洲和亚洲的区域排放，比对温室气体更为敏感。这些降水响应与射流的变化和湿气通量的变化是一致的。尽管PDRMIP模拟的理想性质无法正式归因，但我们的结果表明，气溶胶会扰乱美国西海岸的降水和淡水资源。