Evaluating the role of latent heating in extratropical cyclone development using a new cyclone climatology

在中纬度地区，人们观察到北大西洋会形成气旋。这些气旋可能会爆炸性地发展，在英国和西欧造成洪水和严重的风灾。在东大西洋形成的气旋由于其规模小和发展迅速，特别难以预测。研究表明，一系列广泛的过程可能对它们的发展很重要。然而，导致其发展的主要机制仍不清楚。一个这样的过程是释放潜热进入旋风。当空气上升时，它会冷却，如果水蒸气凝结，这种能量就会以凝结潜热的形式释放到大气中。大量的热量因此释放到大气中，导致空气上升。垂直速度的增加伴随着低层辐合和高层辐散的增加，这导致气旋环流的增加，从而导致气旋加强。观测案例研究表明，潜热加热本身不能形成气旋，但它可以在气旋的发展中发挥重要作用。理论研究表明，气旋越小，潜热加热的潜在影响越大。因此，据推测，东大西洋气旋，通常发生在较小的规模，将强烈影响潜热的释放。此外，有证据表明，未来东大西洋气旋的数量和强度可能增加，潜热的作用可能发挥更重要的作用。因此，了解控制东大西洋气旋发展的因素对于改进当前的气旋预报和气候变化预测都至关重要。在这个项目中，将确定造成中纬度气旋发展的过程;特别是将调查对东大西洋风暴中潜热作用的评价。该项目有三个主要目标：计算新获得的气旋数据集的结构演变;根据其结构演变对这些气旋进行分类;以及确定潜热在其发展中的相对贡献。研究结果将与区域气候预测界有关，他们将能够使用由此产生的数据集来验证气候模型模拟的气旋。这是了解当前模型性能和使模型旋风用于未来影响研究的重要一步。了解气旋结构及其相关影响对保险业和灾难建模者也有好处。

In the mid-latitudes cyclones are observed to form in the north Atlantic. These cyclones can develop explosively causing flooding and severe wind damage in the UK and Western Europe. Cyclones that form in the east Atlantic can be particularly hard to forecast owing to their small scales and rapid development. Studies have shown that a wide range of processes may be important for their development. However, the dominant mechanism responsible for their development remains unclear. One such process is the release of latent heat into the cyclone. As air rises, it cools and, if water vapour condenses, this energy is released into the atmosphere as latent heat of condensation. A large amount of heat is thus released into the atmosphere causing air to rise. The increase in vertical velocity is accompanied by an increase in low-level convergence and upper-level divergence which leads to an increase in cyclonic circulation and hence cyclone intensification. Observational case studies have shown that latent heating by itself cannot form a cyclone but it can play an important role in their development. Theoretical studies have shown that the smaller the cyclone, the greater the potential impact of latent heating. Thus it is hypothesised that east Atlantic cyclones, which generally occur on smaller scales, will be strongly influenced by the release of latent heat. Furthermore, there is evidence to suggest that the number and intensity of east Atlantic cyclones may increase in the future and that the role of latent heating may play a more important role. Thus it is vital for both improvement of the current cyclone forecasts and for climate change predictions that we understand the factors controlling the development of east Atlantic cyclones. In this project the processes responsible for the development of mid-latitude cyclones will be determined; in particular an evaluation of the role of latent heating in east Atlantic storms will be investigated. The project has three main aims; to calculate the structural evolution of a newly available dataset of cyclones; to classify these cyclones according to the evolution of their structure; and to determine the relative contribution of latent heating in their development. The research findings will be of relevance to the regional climate predication community who will be able to use the resulting dataset to verify climate model simulated cyclones. This is an essential step towards understanding current model performance and allowing model cyclones to be used in future impacts studies. Understanding cyclone structures and their related impacts is also of benefit to the insurance industry and catastrophe modellers.