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

随着气候因温室气体增加而变暖，北极海冰面积9月最小值大幅减少，夏季北极浮冰漂移速度加快，这归因于冰层变薄。与此同时，人类在北极的活动也在扩大，越来越多的居民和游客利用减少的海冰面积在夏季进行航运和海上作业。这导致了对北极地区天气、海洋和海冰状况的预报的需求，做出决策所需的时间尺度通常从几个小时到几周不等。随着我们转移到“新北极”，那里的边缘冰带预计将主导夏季北冰洋，我们预计由于冰川边缘，表面阻力将增加，这可能会加强地面与北极天气系统的相互作用。不幸的是，目前的预报技能在北极地区比在北中纬度地区更具变数。预测的新前沿是对这一耦合系统进行建模，并具有保真度和技巧。然而，由于对物理过程的了解还不完全，北极天气系统预报的改进尚未实现。北极气旋是夏季影响北极环境的主要危险天气系统类型，也可能对海冰运动产生关键影响。该项目的目的将是将北极气旋与研究较多的中纬度气旋区分开来的机制区分开来，并确定这些机制是否使它们更难预测，或者是否与下方动态海冰表面的耦合导致预测技能较低。然后将研究不同的方法，以确定是否可以改进预测。该项目将气旋动力学和与海冰耦合的建模和理论方法结合在一起。我们将使用新的方法来询问预报模型的运行情况，并确定表面特性改变气旋增长的机制。主要的工具将是最先进的ECMWF全球大气模式，包括与海冰模式耦合和不耦合的模式。PHD项目将分三个阶段进行：1)分析与延长的YOPP周期(3年)的物理过程趋势存档的ECMWF业务预报，2)使用综合的ECMWF模式但在简化的配置中进行实验，以检查气旋发展对不同环境的敏感性，以及3)在真实情况下通过耦合物理和海冰模式本身的变化来改变与海冰的耦合。该项目将设在雷丁大学气象系，并与ECMWF和俄克拉荷马大学合作。ECMWF全球耦合地球系统模式将被用于新的实验，在ECMWF的支持下运行该模式并使用ECMWF超级计算资源。这将需要在ECMWF工作的场合，除了计算机模拟，该项目可能涉及理论的发展(建立在现有的中纬度气旋理论基础上)和使用新的观测，这取决于你的技能和优势以及你选择的项目方向。你将接受大气层动力学和物理、全球数值模拟以及ECWMF数值天气预测课程的硕士级培训。该项目与薄冰国际项目相联系，该项目计划在2021年夏天进行一项飞机实验，旨在观察北极气旋和下面不断变化的海冰状态。学生基金将包括在美国俄克拉何马大学的研究安置，与薄冰项目团队和他们的北极和南极研究小组。您将有机会加入北极飞行计划任务团队，进行飞机试验。

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.