Understanding the Role of Mesoscale Atmosphere-Ocean Interactions in Seasonal-to-Decadal Climate Prediction

对逐年气候变化的熟练预测将具有巨大的价值，例如，干旱的提前预警将有助于农民、水资源管理者和救济机构科普水资源短缺的困难。气候变化在多大程度上是可预测的尚不清楚，但厄尔尼诺现象的例子表明，可预测的变化可能来自大气和海洋之间的相互作用。最近的研究表明，可预测的气候变化也可能是与墨西哥湾流和黑潮海流有关的大气-海洋耦合的结果。假设耦合的一个关键方面是小的空间尺度的参与，特别是大气响应的墨西哥湾流和黑潮电流和周围冷水的温暖沃茨之间的强烈和狭窄的温度对比。 同时，海洋对大气的响应可能涉及到海洋锋面的中尺度动力学，通过这些锋面，表面风可以引起深层垂直运动。 深部运动很重要，因为它们可以将大气与变化缓慢发生的海洋水平联系起来，从而创造出熟练的长期预测的潜力。这里进行的研究探索了与海气耦合相关的可预测性的潜力，使用气候模型模拟在足够高的分辨率下进行，以捕捉机制。该研究还着眼于高分辨率捕捉与气候变化相关的极端天气的潜力，例如与厄尔尼诺事件相关的飓风和大气河流分布的变化。具体而言，主要研究人员（PI）使用社区地球系统模型（CESM，版本1.3）进行模拟，大气层网格间距为0.25度，海洋网格间距为0.1度。这些模拟包括1920年至2100年未初始化的10人瞬态气候模拟集合，以及从1982年至2016年开始的回顾性5年气候预测集合。 为了探索小规模机制的影响，采取了一些战略，例如在海洋模型产生的海面温度输入大气模型之前进行平滑处理的实验，从而使小规模相互作用机制失效。因此，努力确定气候系统实际上可预测的程度以及决定其可预测性的物理机制，具有广泛的影响。该项目的更广泛影响还得益于开放获取该项目产生的模拟，这使世界各地的研究人员能够参与气候系统可预测性的研究。 PI还通过包括名为“海洋”的广播节目和国际CLIVAR暑期学校在内的场地与研究界和公众进行外联。 更广泛的教育影响来自于PI参与其部门的本科生研究经验计划，并通过支持和培训博士后助理和研究生。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Skillful predictions of year-to-year climate variations would have tremendous value, for instance advanced warning of droughts would help farmers, water managers, and relief agencies cope with the hardships of water scarcity. The extent to which climate variations are predictable in general is not known, but the example of El Nino shows that predictable variations can arise from interactions between the atmosphere and the ocean. Recent research suggests that predictable climate variations could also result from atmosphere-ocean coupling associated with the Gulf Stream and the Kuroshio Current. A critical aspect of the hypothesized coupling is the involvement of small spatial scales, in particular the atmospheric response to the strong and narrow temperature contrasts between the warm waters of the Gulf Stream and Kuroshio currents and the surrounding cold water. Meanwhile the ocean's response to the atmosphere could involve the mesoscale dynamics of sharp ocean fronts, through which surface winds can induce deep vertical motions. Deep motions are important as they can connect the atmosphere with levels in the ocean where variability takes place slowly, thus creating the potential for skillful long-lead prediction.Research conducted here explores the potential for predictability associated with air-sea coupling using climate model simulations performed at high enough resolutions to capture the mechanisms. The research also looks at the potential for high resolution to capture the weather extremes associated with climate variability, for example changes in the distribution of hurricanes and atmospheric rivers associated with El Nino events. Specifically, the Principal Investigators (PIs) perform simulations using the Community Earth System Model (CESM, version 1.3) with 0.25 degree grid spacing for the atmosphere and 0.1 degree spacing for the ocean. The simulations include a 10-member ensemble of uninitialized transient climate simulations from 1920 to 2100, as well as an ensemble of retrospective 5-year climate predictions starting from years between 1982 and 2016. A number of strategies are pursued to explore the impact of small-scale mechanisms, such as experiments in which the sea surface temperatures produced by the ocean model are smoothed before they are fed into the atmospheric model, thereby disabling small-scale interaction mechanisms.Skillful predictions of climate variability could have tremendous societal value, as noted above, thus work to establish the extent to which the climate system is in fact predictable, and the physical mechanisms that determine its predictability, has substantial broader impacts. The broader impacts of the project are also served by open access to the simulations generated in the project, which allows researchers around the world to engage in research on climate system predictability. The PIs also engage in outreach to the research community and the general public through venues including a radio program titled "On the Ocean" and International CLIVAR summer schools. Educational broader impacts come from the PIs' participation in their department's Research Experiences for Undergraduates program, and through the support and training of a postdoctoral associate and a graduate student.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.