Diabatic influences on current and future hazardous Mediterranean cyclones

地中海盆地是各种风暴的发源地，从空气与山脉相互作用产生的弱系统到强烈的气旋(也被称为“低地”)。地中海飓风是气旋的一个子集，与飓风相似，可能特别具有破坏性；例如，2020年在希腊登陆时，梅丹娜飓风的风力相当于二级飓风，造成基础设施破坏和人员伤亡。与横跨北大西洋的地中海气旋相比，人们对地中海气旋的研究要少得多，尽管地中海气旋造成了当地冬季极端降水的80%。由于它们的规模通常较小，寿命较短；附近的山脉和温暖的半封闭地中海对它们的发展和影响的影响；以及亚热带和温带气候带的影响，它们的预测更具挑战性。这些气旋是由不同空间尺度上发生的过程之间的相互作用驱动的：来自海洋表面的热量和水汽通量以及来自深对流云的潜热通量(所谓的非绝热过程)，以及极地急流在大约10公里高度的行星尺度偏差，造成通常在其形成之前的侵入气流。研究表明，地中海地区特别容易受到气候变化的影响，随着气候变暖，可能会有更少但更危险的药物。我们建议对非绝热过程在当前和未来气候中推动危险地中海气旋发展的作用产生新的认识。目的是*量化非绝热过程对强烈地中海气旋的影响，并确定它们如何改变气旋的路径和强度及其危险的风和降雨量；*模拟和分析看似最坏的地中海气旋随气候变化的变化，并量化非绝热影响的变化的重要性；考虑到对预报和气候变化缓解的影响以及对地中海以外相关天气系统的适用性，特别是副热带气旋，综合所获得的知识。重要的是，我们使用的大气数值模式将有一个模型网格，各点之间只有几公里的距离，足够精细，能够直接表示深对流，而不是已知错误地表示对流和更大尺度之间的相互作用的近似。我们将把这个大气模型和一个海洋模型结合起来，即所谓的耦合，以评估通过海洋混合引起的海洋表面温度变化的重要性。这种千米尺度的耦合模型是最先进的，现在只有通过环境预测模型的进步才能实现。我们将使用先进的诊断工具来询问我们的模型输出，以跟踪从它们的产生到天气影响的非绝热过程。对于我们的气候变化工作，我们将利用新的社区大型集合气候变化模拟来推动我们的千米级气旋预测。其好处将是(1)关于空间尺度上非绝热过程重要性的新的过程级知识，(2)对未来可能出现的最坏情况的气旋的洞察，(3)用于表示气旋的千米级耦合模式的成本效益分析，(4)包括研究结果对全球相关天气系统的影响的综合研究，以及(5)英国在地中海盆地上空进行千米级耦合模拟的新研究能力。这些好处将通过我们与我们的项目伙伴(包括气象局)的密切合作和参与由欧盟成本行动资助的活跃的地中海气旋跨学科研究网络而转化为影响。

The Mediterranean basin is home to diverse storms from weak systems generated by air interacting with mountains to intense cyclones (also termed "depressions"). A subset of cyclones, medicanes (Mediterranean hurricanes), resemble hurricanes and can be particularly devastating; e.g., the winds of medicane Ianos were equivalent to a category two hurricane on its landfall in Greece in 2020 causing infrastructure damage and fatalities. Mediterranean cyclones have been far less studied than their relatives crossing the North Atlantic, despite being responsible for up to 80% of the local winter-time extreme precipitation. They are more challenging to forecast due to their typically smaller scale and shorter lifetime; the effects of the nearby mountains and warm, semi-enclosed Mediterranean Sea on their development and impacts; and the influence of both the subtropical and extratropical climatic zones. These cyclones are driven by interactions between processes occurring at different spatial scales: fluxes of heat and moisture from the ocean surface together with latent heat fluxes from deep convective clouds (so-called diabatic processes), and planetary-scale deviations of the polar jet at about 10km altitude that cause the intruding air streamers that commonly precede their genesis. Studies indicate that the Mediterranean region is particularly vulnerable to climate change and as the climate warms there will likely be fewer, but more hazardous, medicanes. We propose to generate new knowledge of the role of diabatic processes in driving the development of hazardous Mediterranean cyclones in both the current and future climate.The aims are to * Quantify the influence of diabatic processes on intense Mediterranean cyclones and determine how they modify the track and intensity of cyclones and their hazardous winds and rainfall; * Simulate and analyse changes in plausible worst case Mediterranean cyclones with climate change and quantify the changing importance of diabatic influences; and * Synthesize the knowledge gained considering implications for forecasting and climate change mitigation and applicability to related weather systems beyond the Mediterranean, particularly subtropical cyclones.Importantly, the atmospheric numerical model we use will have a model grid with points separated by just a few km, fine enough to be able to directly represent deep convection without the approximations that are known to misrepresent interactions between convection and larger scales. We will combine this atmospheric model with an ocean model, so-called coupling, to assess the importance of changes in the sea surface temperatures through ocean mixing. Such km-scale coupled modelling is state-of-the-art and is only now possible through advances in environmental prediction modelling. We will interrogate our model output using advanced diagnostic tools to trace the diabatic processes from their generation to weather impacts. For our climate change work we will leverage new community large-ensemble climate change simulations to drive our km-scale cyclone forecasts.The benefits will be (1) new process-level knowledge of the importance of diabatic processes across spatial scales, (2) insight into plausible worst-case future cyclones, (3) cost-benefit analysis of km-scale coupled models for cyclone representation, (4) a synthesis that includes the implications of the findings for related weather systems across the globe, and (5) a new UK research capability for km-scale coupled modelling over the Mediterranean basin. These benefits will translate into impacts through our close collaboration with our project partners (including the Met Office) and engagement in active Mediterranean cyclones interdisciplinary research networks funded by EU COST Actions.