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

点击翻译按钮获取中文摘要

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.