Orographic Flows off Greenland and their Impact on the Ocean

科学背景格陵兰岛在大气中扮演着屏障的角色，因此迫使许多地形风，例如在其侧翼的屏障流和在冰盖最陡峭部分的垂直流。屏障流平行于山脉，低于山脉高度，大致处于地转平衡状态。倾斜流大致沿坡而下，很浅，受地表净冷却的密度梯度的强迫。这些地形流极大地影响了邻近的格陵兰海、冰岛海和伊尔明格海的大尺度大气环流和空气-海冰相互作用。此外，格陵兰岛周围的海冰和冰盖本身都因人为气候变化而发生了巨大变化，这正在改变这些地形流在气候系统中的作用。格陵兰海和冰岛海目前是人们关注的焦点，因为它们承载着产生大西洋经向翻转环流源头的关键过程。最近已经证明，格陵兰岛东部的变率主导着AMOC的变率；这里海冰的消退正在影响这一地区致密水的生成。研究计划在这个项目中，你将研究格陵兰岛东北部的障碍风和垂直气流，这是一个从未被研究过的地区。您将使用最先进的数值模型和观测模拟来检查几个案例研究。您将使用最新的气象再分析产品将这些放入气候环境中。您将对耦合气候模型的输出进行分析，以确定这些流在不同海冰条件下对海洋的气候影响。你的研究将集中在格陵兰岛东南部的障碍风和垂直气流上，2007年和20世纪90年代末在那里进行了飞机观测。但请关注格陵兰岛东北部，那里的研究要少得多，但现在这里的海冰面积在夏季和冬季都有所减少。您将研究这些地形流对海洋和气候系统的变化作用。培训和技能你将接受培训，运行和分析大气的数值模拟；并分析气候模式的大气和海洋成分的输出。数值模型将是MetUM（英国气象局大气统一模型）和HadGEM3（英国气象局气候模型的一个配置）。MetUM是英国气象局最先进的数值天气预报模型，用于业务天气预报、研究和所有气候模型的一部分。管理团队在使用和开发MetUM方面拥有丰富的经验。您需要成为使用Python和/或Matlab进行数据分析的专家。最近的冰岛-格陵兰海洋项目和2007年的格陵兰流动扭曲实验的飞机观测结果将可用，2021年8月资助的夏季北极气旋野外运动的新飞机观测结果也将相关。首席主管将共同领导这次活动，并将建议飞行一些地形流任务作为次要目标。此外，格陵兰海岸为数不多的气象站将提供例行观测。

Scientific backgroundGreenland acts as a barrier in the atmosphere so forces a number of orographic winds, such as barrier flows at its flanks and katabatic flows over the steepest parts of the ice sheet. Barrier flows run parallel to the mountains, below mountain height and approximately in geostrophic balance. Katabatic flows run approximately down slope, are shallow and are forced by density gradients from net cooling at the surface. These orographic flows dramatically affect the large-scale atmospheric circulation and the air-sea-ice interactions in the adjacent Greenland, Iceland and Irminger Seas. Furthermore, both the sea-ice around Greenland and the ice sheet itself are changing dramatically in response to anthropogenic climate change and this is changing the role of these orographic flows in the climate system. The Greenland and Iceland Seas are currently a major focus of attention as they host key processes that generate the headwaters of the Atlantic Meridional Overturning Circulation. It has recently been demonstrated that variability to the East of Greenland dominates the variability of the AMOC; and that the retreating sea-ice here is impacting the generation of dense water in this region. Research plansIn this project, you will examine barrier winds and katabatic flows over Northeast Greenland - a region where they have never been studied. You will examine several case studies using simulations from a state-of-the-art numerical model and observations. You will place these into a climatological context using the latest meteorological reanalyses products. And you will carry out an analysis of coupled climate model output to determine the climatological impact of these flows on the ocean under different sea-ice conditions. You will build on research focused on barrier winds and katabatic flows off SE Greenland, where aircraft-observations were made in 2007 and the late 1990s. But focus on NE Greenland, which has been far less studied, but is now the location of reduced sea-ice extents in both summer and winter. You will investigate the changing role of these orographic flows on the ocean and the climate system. Training and skills You will be trained to run and analyse numerical simulations of the atmosphere; and analyse output from both the atmospheric and oceanic components of a climate model. The numerical models will be the MetUM (the Met Office Unified Model of the atmosphere) and HadGEM3 (a configuration of the Met Office's climate model). The MetUM is the Met Office's state-of-the-art numerical weather prediction model, used for operational weather forecasting, research and as part of all of their climate models. The supervisory team have extensive experience of using and developing the MetUM. You will need to become an expert in data analysis using Python and/or Matlab. Aircraft observations from the recent Iceland Greenland Seas Project - and the Greenland Flow Distortion Experiment in 2007 - will be available and new aircraft observations from a funded Summertime Arctic Cyclones field campaign in August 2021 should also be relevant. The lead supervisor is co-leading this campaign and will suggest flying some orographic flow missions as secondary objectives. In addition, routine observations from the few meteorological stations on the coast of Greenland will be available.