Fundamental Mechanisms of Arctic Summer-time Cyclone Growth and Sea-ice Interaction

由于温室气体增加，气候变暖，9月北极海冰面积最小值急剧减少，夏季北极浮冰的漂移速度加快，这归因于冰层变薄。与此同时，人类活动在北极范围内扩大，更多的居民和游客在夏季利用减少的海冰范围进行航运和海上作业。这推动了对整个北极地区天气、海洋和海冰状态的预测需求，这些预测需要在时间尺度上做出决定，通常从几小时到几周不等。当我们移动到“新北极”，在那里，边缘冰区预计将主导夏季北冰洋，我们预计，表面阻力将增加，由于冰缘边缘，这可能会增强表面与北极天气系统的相互作用。不幸的是，目前北极地区的预报技术比北方中纬度地区的预报技术更多变。预测的新领域是用精确度和技巧来模拟这种耦合系统。然而，由于对北极天气系统物理过程的认识还不完全，北极天气系统的预测还有待改进，北极气旋是夏季影响北极环境的主要灾害性天气系统，也可能对海冰运动产生重要影响。该项目的目的是将北极气旋与研究较多的中纬度气旋区别开来的机制分离出来，并确定这些机制是否使它们的可预测性降低，或者与下面动态海冰表面的结合是否是造成预测能力较低的原因。然后将研究不同的方法，看看是否可以改进预测。该项目将旋风动力学和海冰耦合的模型和理论方法结合起来。我们将使用新的方法来询问预测模型，因为他们运行和确定的机制，通过表面特性改变气旋的增长。主要工具将是欧洲中期天气预报委员会最先进的全球大气模型，有或没有与海冰模型耦合。博士项目将分为三个阶段：1）分析欧洲中期天气预报中心（ECMWF）的业务预报，其中包括延长的YOPP期间（3年）的物理过程趋势，2）使用综合ECMWF模式但在简化配置中进行的实验，以检查气旋发展对变化环境的敏感性;在真实的情况下，通过改变耦合物理和海冰模型本身，改变与海冰的耦合，进行预测。阅读大学与ECMWF和俄克拉荷马州大学合作。ECMWF全球耦合地球系统模型（IFS）将在ECMWF的支持下用于新的实验，以运行模型并使用ECMWF超级计算资源。这将需要在ECMWF工作的机会。除了计算机建模，该项目可能涉及理论发展（建立在现有的中纬度气旋理论上）和使用新的观测结果的组合，这取决于你的技能和优势以及你选择的项目方向。您将接受大气动力学和物理学、全球数值模拟以及ECWMF数值天气预报课程的硕士级培训。该项目与THINICE国际项目相联系，该项目计划在2021年夏季进行飞机实验，旨在观察北极气旋和下面不断变化的海冰状态。学生资助将包括在俄克拉荷马州（美国）大学的研究实习，与THINICE项目团队及其北极和南极研究小组合作。您将有机会加入北极的飞行计划使命团队，进行飞机实验。

As the climate has warmed in response to increasing greenhouse gases, the September minimum in Arctic sea-ice extent has decreased dramatically and the drift speed of summer Arctic pack ice has increased, attributed tothinner ice. At the same time, human activity has expanded within the Arctic, with more residents and visitorsmaking use of the reduced sea ice extent for shipping and offshore operations in summer. This has drivendemand for forecasts of weather, ocean and sea-ice state across the Arctic on timescales needed to makedecisions, typically ranging from hours to weeks. As we move to the "new Arctic", where the marginal ice zoneis projected to dominate the summer Arctic Ocean, we anticipate that surface drag will increase due to the icefloe edges and this may enhance surface interactions with Arctic weather systems. Unfortunately, currentforecast skill is more variable in the Arctic than the northern mid-latitudes. The new frontier in prediction is tomodel this coupled system with fidelity and skill. However, improvements in Arctic weather system prediction have yet to be realized because understanding of the physical processes is incomplete.Arctic cyclones are the dominant type of hazardous weather system affecting the Arctic environment in summerand can also have critical impacts on sea-ice movement. The aim of the project will be to isolate the mechanisms that distinguish Arctic cyclones from the much studied mid-latitude cyclones and to determine whether these mechanisms render them less predictable, or whether the coupling with the dynamic sea ice surface beneath is responsible for the lower forecast skill. Different approaches will then be investigated to see if prediction can be improved.The project brings together modelling and theoretical approaches to cyclone dynamics and coupling with sea-ice. We will use novel approaches to interrogate forecast models as they run and determine the mechanisms through which the surface properties alter cyclone growth. The primary tool will be the state-of-the-art ECMWF global atmospheric model with and without coupling to a sea ice model. The PhD project will evolve in 3 stages: 1) analysis of operational ECMWF forecasts archived with physical process tendencies for the extended YOPP period (3 years), 2) experiments using the comprehensive ECMWF model but in simplified configurations to examine sensitivity of cyclone development to varying environment and 3) re-forecasts in real cases varying the coupling with the sea ice through changes in the coupling physics and sea ice model itself.The project will be based in the Department of Meteorology, University of Reading and partnerwith the ECMWF and University of Oklahoma. The ECMWF global coupled earth system model (IFS) will beused for new experiments with support from ECMWF to run the model and use of ECMWF supercomputingresources. This will entail occasions working at the ECMWF.In addition to the computer modelling, the project could involve a combination of the development of theory(building on existing theory for mid-latitude cyclones) and use of new observations, depending on your skill setand strengths and the direction you chose to take the project. You will receive masters-level training in thedynamics and physics of the atmosphere, global numerical modelling, as well as the ECWMF course onNumerical Weather Prediction.The project links in with the THINICE international project which plans an aircraft experiment in summer 2021aiming to observe Arctic cyclones and the evolving sea ice state below. The studentship funding will involve aresearch placement at the University of Oklahoma (USA), with the THINICE project team and their Arctic andAntarctic Research Group. You will have the opportunity to join the flight planning mission team in the Arctic to conduct the aircraft experiment.