NSFGEO-NERC: Large-Scale Atmospheric Circulation Response to Oyashio Extension Frontal Variability

北太平洋的冬季以无休止的锋面风暴为特征，这些风暴在日本附近形成，并在穿越海洋到达北美时不断增加。即使海表面温度(SST)保持不变，模式模拟也能产生真实的北太平洋风暴，这表明风暴的存在是由于强大的高空急流和伴随的南北大气温度差异，而不是海气相互作用。然而，有耐人寻味的迹象表明，风暴行为可能会受到底层SST变化的影响，一些迹象表明，缓慢变化的SST可能会改变风暴路径和行为，这可能被证明对做出长期天气预报有用。人们感兴趣的海温变化是黑潮-Oyashio延伸(KOE)蜿蜒的结果，KOE是一种从日本海岸延伸到太平洋的狭窄洋流。KOE是一种暖流，当KOE向北或向南移动时，海流与其以北的冷水之间的强烈温差会产生较强的SST变化。但首席调查员(PI)和其他人最近的工作表明，捕捉大气响应的关键是大幅提高用于此目的的大气模型的分辨率。特别是，私营部门开发了社区大气模式第六版(VR-CAM6)的可变分辨率版本，该版本利用光谱元素动力核心来提高北太平洋的分辨率(框从北纬20N到北纬60N，东经130W到西经110W)。北太平洋以外的较低分辨率使模式的运行成本足够低，可以进行大量的模拟，对每个施加的SST异常模式进行60个或更多的单独模拟，从而即使是微弱的大气响应也可以被捕获和分析。在确定大气对与KoE相关的SST变化的响应方面的另一个优势是一个简化的海洋模型，它允许近地表海洋对地面风和其他大气强迫的变化做出反应。该模型被称为“铅笔”海洋模型，或PenOM，因为它代表了表层大气每个网格框下方的一列海洋中热量的上下传递。PEOM没有模拟洋流中水的横向运动，但该奖项下的工作增加了表示由于埃克曼输送引起的SST变化的能力，这意味着由科里奥利力作用于水面风推动的水造成的侧向漂移。由于其与上面提到的长期天气预报的相关性，该工作具有社会和科学兴趣。此外，具有Ekman传输的PenOM配置将通过共同体地球系统模型提供给全球研究社区，作为其更简单的模型配置套件的一部分。这项工作通过与伦敦帝国理工学院Arnaud Chaaja博士的合作，通过下文所述的安排，促进了大气研究方面的国际合作。此外，该项目还支持若干外联活动，包括制作一个以模型模拟和研究结果为特色的教育短片。该项目还为博士后研究协会提供支持和培训。该项目由国家科学基金会地球科学局(NSF/GEO)和英国国家环境研究委员会(NERC)通过NSF/GEO-NERC牵头机构协议共同资助。该协定允许美国和英国提交一个单一的联合提案，并由该机构进行同行审查，该机构的调查员在预算中所占比例最大。在成功地共同确定一个奖项后，每个机构将为与其本国相关的预算和调查人员的比例提供资金。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Winter over the North Pacific features an endless parade of frontal storms, forming near Japan and building as they cross the ocean to reach North America. Model simulations can produce realistic North Pacific storms even if the sea surface temperatures (SSTs) are held fixed, indicating that the storms owe their existence to the strong upper-level jet stream and accompanying north-south atmopsheric temperature contrast rather than air-sea interactions. Nevertheless there are intriguing hints that storm behavior can be influenced by variations in the underlying SSTs, and some indications that slowly varying SSTs may change storm paths and behavior in ways that could prove useful for making long-range weather predictions. The SST variations of interest occur as a result of the meandering of the Kuroshio-Oyashio Extension (KOE), a narrow ocean current that extends into the Pacific from the coast of Japan. The KOE is a warm current and the sharp temperature contrast between the current and the cold water north of it produces relatively strong SST variations when the KOE shifts to the north or south.Attempts to identify and analyze the influence of KOE-related SST variations on storms and atmospheric circulation have had mixed results. But recent work by the Principal Investigators (PIs) and others suggests that the key to capturing the atmospheric response is to dramatically increase the resolution of atmospheric models used for this purpose. In particular the PIs have developed a variable resolution version of the Community Atmosphere Model version 6 (VR-CAM6) which takes advantage of the spectral element dynamical core to increase resolution over the North Pacific (a box from 20N to 60N and 130E to 110W). The lower resolution outside the North Pacific allows the model to be run cheaply enough to allow large ensembles of simulations, with 60 or more separate simulations for each imposed SST anomaly pattern, so that even weak atmospheric responses can be captured and analyzed.A further asset in identifying the atmospheric response to KOE-related SST variations is a simplified ocean model which allows the near-surface ocean to respond to changes in surface winds and other atmospheric forcing. The model is referred to as a "pencil" ocean model, or PenOM, because it represents the up and down transfer of heat in a column of the ocean below each grid box of the surface atmosphere. PenOM does not simulate the lateral movement of water in ocean currents, but work under this award adds the capability to represent changes in SST due to Ekman transport, meaning the sideways drift caused by the Coriolis force acting on water pushed along by the surface wind.The work is of societal as well as scientific interest due to its relevance to long-term weather prediction as noted above. Also, the PenOM configuration with Ekman transport will be made available to the worldwide research community through the Community Earth System Model as part of its suite of simpler model configurations. The work promotes international collaboration in atmospheric research through its collaboration with Dr. Arnaud Czaja at Imperial College London, through the arrangement noted below. Also, the project supports several outreach activities including the production of a short educational video featuring model simulations and research results. The project also provides support and training to a postdoctoral research associate.This project is jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF/GEO) and the National Environment Research Council (NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. The Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own country.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.