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

[财经] 非洲东风波变化和大尺度环境对大西洋飓风的作用：观测和模型模拟

• 批准号: NE/I018891/1
• 负责人: Kevin Hodges
• 金额: $ 8.58万
• 依托单位: University of Reading
• 依托单位国家: 英国
• 项目类别: Training Grant
• 财政年份: 2011
• 资助国家: 英国
• 起止时间: 2011 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI018891%2F1
• 关键词: FINANCE; role; African; Easterly; Wave

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.

非洲东风波（AEWs）是西非和热带大西洋气候的组成部分。它们在季风月份（6月至9月）调节西非的日降雨量，并可能影响下游热带气旋形成的可能性（Hopsch et al., 2010）。它们还涉及大量矿物粉尘从北非穿过大西洋到加勒比海的产生和运输（Jones et al., 2004），这可以改变西非季风环流，也与热带气旋的发展相互作用（Jury和Santiago， 2010）。此外，大西洋85%的“主要”飓风（即在Saffir Simpson尺度上达到3级或以上的飓风）都是由AEWs发展而来的（Landsea, 1993），这反过来又导致了美国东海岸的经济和保险损失（Lott和Ross， 2006）。尽管它们很重要，但AEW发生和演化的细节还没有得到很好的理解。特别是，我们对影响预警机是否会在非洲西海岸附近发展并产生热带气旋的过程的了解很少。该项目的目的是增进对与预警有关的飓风发展的物理过程的了解，以及它们与大尺度环境的相互作用，以期建立一个增强的大西洋气旋季节性预报方案，其结果可以提供给更广泛的科学界和商界。特别强调与非洲东风急流（AEJ）和热带东风急流相关的AEWs的季节内和年际变化，特别是在沙尘存在和海表温度（SST）可能起的作用。这项研究的动机有两个方面。首先，需要更好地了解控制大西洋AEW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动力与对流的相互作用。在过程相关相互作用的连续体中，短时间尺度对长时间和大空间尺度的反馈。因此，了解AEW发展/衰减的起源将提高飓风预报的可靠性，并为模式开发提供信息。其次，预测对下游的气旋形成很重要，它需要有关热带大西洋天气系统的统计信息。预警数量和强度的变异性。将讨论的具体科学问题有：1。预警系统在季节内和天气时间尺度上的空间分布和变异是什么？哪些预警系统结构触发气旋形成？这些是否与发展中的热带气旋在加勒比海或美国登陆的可能性有关？2. 相对于热带气旋形成的大尺度环境，AEJ-AEW动力学的作用是什么？干燥空气（中纬度或撒哈拉地区）和沙尘如何影响预警和热带气旋（TC）的发展？对机制的更好理解能提高大西洋tc的可预测性吗？3. 海温异常和相关的大尺度对流模式在季节内和年际时间尺度上对决定AEW变率的性质有多重要？这对在加勒比海和美国登陆的风暴数量有何影响？在3年的时间里，学生将接受科学、计算和诊断工具方面的培训，用于支持和影响关键业务决策所需的研究。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型学术，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在灾难建模前沿的刺激环境。