[FINANCE] The role of African Easterly Wave variability and the large-scale environment on Atlantic Hurricanes: Observations and model simulations

非洲东风波是西非和热带大西洋气候的组成部分。它们调节西非季风月(6月至9月)的日降雨量，并可影响下游热带气旋发生的可能性(Hopsch等人，2010年)。它们还与大量矿物粉尘的产生和从北非横渡大西洋运往加勒比海有关(Jones等人，2004年)，这可能会改变西非季风环流，也会与热带气旋的发展相互作用(JUAR和圣地亚哥，2010年)。此外，大西洋上85%的“主要”飓风(即达到Saffir Simpson等级3级或以上的飓风)来自AEW(LandSea，1993)，这反过来又推动了美国东部海上的经济和保险损失(Lott和Ross，2006)。尽管它们很重要，但AEW的起源和进化的详细方面还没有被很好地理解。特别是，我们对影响AEW是否会在非洲西海岸附近发展并产生热带气旋的过程的理解很差。该项目的目的是增进对加强和抑制与AEW有关的飓风发展的物理过程及其与大尺度环境的相互作用的了解，以期为大西洋气旋制定一个改进的季节预报计划，其结果可向更广泛的科学界和企业界提供。将特别重视与非洲东风急流和热带东风急流有关的AEW的季节内和年际变化，特别是在有沙尘和海面温度可能发挥的作用的情况下。这项研究的动机是双重的。首先，有必要更好地了解支配大西洋上空气旋环流演变的关键大气、陆地和海洋相互作用，以及季节内和更短时间尺度上的动力和对流之间的相互作用。短时间尺度在更长的时间和更大的空间尺度上，在与过程相关的互动的连续体中提供反馈。因此，了解AEW发展/衰退的原因将提高飓风预报的可靠性，并为模式的发展提供信息。其次，预报对下游气旋生成很重要，它需要热带大西洋天气系统的统计信息，例如。AEW的数量和强度的变异性。将解决的具体科学问题是：1.在季节内和天气时间尺度上，AEW的空间分布和变异性是什么，以及AEW结构触发气旋发生的原因是什么？这些是否与发展中的热带气旋登陆加勒比海或美国的可能性有关？2.AEJ-AEW动力相对于热带气旋发生的大尺度环境有什么作用。干燥空气(中纬度或撒哈拉沙漠起源)和沙尘如何影响AEW和热带气旋(TC)的发展？更好地理解这些机制能提高大西洋热带气旋的可预测性吗？3.在季节内和年际时间尺度上，海温异常和相关的大尺度对流模式对确定AEW变率的性质有多重要？这对登陆加勒比海和美国的风暴数量有何影响？在三年多的时间里，学生将接受支持和影响关键商业决策所需研究的科学、计算和诊断工具方面的培训。他们将受益于雷丁一流的研究环境，可以获得理学硕士课程，以及在许多令人兴奋的气象学基础和应用领域工作的大量学术、研究人员和博士生社区，以及位于伦敦市中心的领先保险公司处于巨灾建模前沿的令人兴奋的环境。

African easterly waves (AEWs) are an integral part of the West African and tropical Atlantic climate. They modulate daily rainfall over West Africa during the monsoon months (June to September) and can impact the probability of downstream tropical cyclogenesis (Hopsch et al., 2010). They are also implicated in the generation and transport of large quantities of mineral dust from North Africa across the Atlantic to the Caribbean (Jones et al., 2004) which can modify the West African monsoon circulation and also interact with the development of tropical cyclones (Jury and Santiago, 2010). Furthermore, 85% of 'major' hurricanes (i.e. those attaining category 3 or above on the Saffir Simpson scale) in the Atlantic develop from AEWs (Landsea, 1993) which in turn drive economic and insured losses on the eastern seabord of the United States (Lott and Ross, 2006). Despite their importance, the detailed aspects of AEW genesis and evolution are not well understood. In particular, our understanding of the processes that influence whether or not an AEW will develop near the west coast of Africa and spawn a tropical cyclone is poor. The aim of this project is to improve understanding of the physical processes that enhance and suppress hurricane development associated with AEWs and their interaction with the large-scale environment with a view to creating an enhanced seasonal forecast scheme for Atlantic cyclones, the results of which could be made available to the wider scientific and business community. Special emphasis will be given to the intraseasonal and interannual variability of AEWs in association with the African Easterly Jet (AEJ) and Tropical Easterly Jet, especially in the presence of dust and the role sea surface temperatures (SST) may play. The motivation for this study is two-fold. Firstly, there is a need to better understand the key atmosphere, land and ocean interactions that govern the AEW evolution over the Atlantic, as well as the interactions between dynamics and convection at intraseasonal and shorter timescales. Short timescales feedback on longer time- and larger space-scales in a continuum of process-related interactions. Therefore understanding the origin of the AEW development/decay will improve the reliability of hurricane forecasts and inform model development. Secondly, prediction, which is important for downstream cyclogenesis, requires information about the statistics of the weather systems in the Tropical Atlantic, eg. the variability of the number and intensity of AEWs. The specific science questions which will be addressed are: 1. What are the AEW spatial distributions and variability at intraseasonal and weather timescales and what AEW structures trigger cyclogenesis? Do these relate to the likelihood of a developing tropical cyclone making landfall in the Caribbean or United States? 2. What is the role of the AEJ-AEW dynamics relative to the large-scale environment for tropical cyclogenesis eg. how do dry air (mid-latitude or Saharan origin) and dust impact AEWs and tropical cyclone (TC) development? Can a better understanding of the mechanisms improve the predictability of Atlantic TCs? 3. How important are SST anomalies and associated large-scale modes of convection on intraseasonal and interannual time scales in determining the nature of the AEW variability? How does this impact the number of storms that make landfall in the Caribbean and United States? Over 3 years, the student will receive training in the science, computing and diagnostic tools for research required to support and influence crucial business decisions. They will benefit from the superb research environment at Reading with access to MSc courses and a large community of academic, research staff and PhD students working in many exciting fundamental and applied areas of meteorology, and the stimulating environment of a leading insurance house at the cutting edge of catastrophe modelling in the heart of the city of London.