Greenland Flow Distortion.

格陵兰岛对北大西洋-西欧区域的大气环流有重大影响；决定了格陵兰海岸周围中尺度（100公里尺度）天气系统的位置和强度，并直接影响当地和欧洲下游的天气尺度（1000公里尺度）天气系统。人们可以想象这个3000米高的巨大屏障会使其上方和周围的气流偏转，也就是说，会扭曲大气气流，产生局部和远程的后果。与当地天气系统相关的飓风强度的风可以在一个对热盐环流（世界海洋的主要环流）的翻转至关重要的区域诱发巨大的海气热通量（每平方米超过600瓦，超过太阳的日平均通量）、水分和动量。因此，气流畸变在控制大气-海洋耦合气候系统中起着关键作用。该项目将通过飞机观测和数值模拟方案，调查格陵兰在确定当地和下游天气系统的结构和可预测性方面的作用。格陵兰流动扭曲实验（GFDex）将提供一些被认为对改变该地区海洋很重要的强烈大气强迫事件（但目前知之甚少）的第一次详细的现场观测：即尖端射流、屏障风和中尺度气旋。尖端射流形成于格陵兰岛的南端，在弗莱尔角，通过强迫流动越过和周围的地形。当大规模气流堆积在格陵兰岛东南海岸时，就会产生障碍风，迫使风与海岸平行。而在东南海岸附近是一个中尺度气旋形成频繁的地区。GFDex还将通过开展上游观测来调查格陵兰岛在大气流量可预测性中的作用，这些观测的“目标”是调查下游流量对上游流量细节的敏感性，并改进随后对欧洲的预测。格陵兰岛的气流扭曲可以引发大规模的大气“罗斯比”波，影响数千公里外和几天后的天气系统。这些波浪本质上是可预测的，因此通过调整我们的观测策略以针对特定区域，可以改进对英国的后续预测。实地活动后的数值模拟实验将用于评估额外的“目标”观测所带来的任何改进。同时，将利用基于飞机的观测对高影响的本地天气系统的进一步数值模拟研究进行评估和改进。这将增加我们对这些系统的了解，并通过与其他观测和数据集的比较，为驱动海洋和气候模型提供准确的海热和水分通量场。

Greenland has a major influence on the atmospheric circulation of the North Atlantic-Western Europe region; dictating the location and strength of mesoscale (100-km scale) weather systems around the coastal seas of Greenland and directly influencing synoptic-scale (1000-km scale) weather systems both locally and downstream over Europe. One can think of this sizeable 3000-m high barrier deflecting flow both over and around itself, i.e. distorting the atmospheric flow, with both local and remote consequences. Hurricane-stength winds associated with the local weather systems can induce large air-sea fluxes of heat (over 600 Watts per square metre, more than the daily average from the sun), moisture and momentum in a region that is critical to the overturning of the thermohaline circulation (the primary circulation of the world's oceans). Hence the flow distortion plays a key role in controlling the coupled atmosphere-ocean climate system. This project will investigate the role of Greenland in defining the structure and the predictability of both local and downstream weather systems, through a programme of aircraft-based observation and numerical modelling. The Greenland Flow Distortion Experiment (GFDex) will provide some of the first detailed in situ observations of the intense atmospheric forcing events that are thought to be important in modifying the ocean in this area (but are presently poorly understood): namely tip jets, barrier winds and mesoscale cyclones. Tip jets form at the southern tip of Greenland, at Cape Farewell, through the forcing of flow over and around the topography. Barrier winds occur when the large-scale flow is piled up against the southeast coast of Greenland, forcing winds parallel to the coast. While located off this southeast coast is an area of frequent mesoscale cyclogenesis. GFDex will also investigate Greenland's role in atmospheric flow predictability by carrying out upstream observations that are 'targeted' at investigating the sensitivity of the downstream flow to the details of the upstream flow and at improving subsequent forecasts over Europe. Greenland's flow distortion can trigger large-scale atmospheric 'Rossby' waves which influence weather systems thousands of kilometres away and several days later. These waves are by nature predictable, so by adapting our observing strategy to target specific areas, improvements in subsequent forecasts over the United Kingdom are possible. Numerical modelling experiments after the field campaign will be used to assess any improvements from the additional 'targeted' observations. While further numerical modelling studies of the high impact local weather systems will be evaluated and refined using the aircraft-based observations. This will increase our understanding of these systems and, through comparisons with other observations and data sets, provide accurate fields of air-sea heat and moisture fluxes for driving ocean and climate models.