Improving Understanding and Prediction of Atlantic Tropical Cyclogenesis

提高对大西洋热带气旋发生的理解和预测

• 批准号: 0758609
• 负责人: Da-Lin Zhang
• 金额: $ 68.55万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-07-15 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0758609&HistoricalAwards=false
• 关键词: Improving; Understanding; Prediction; Atlantic; Tropical

Intellectual merit: The goals/tasks of this research are to (a) perform 6-7 day cloud-resolving simulations of two tropical cyclone (TC) cases associated with African Easterly Waves (AEWs): one of which developed into a hurricane and the other did not; (b) explore the predictability of the two storms; and (c) examine the roles of different environmental conditions and internal dynamics in determining the different TC genesis and evolution scenarios. The following three research questions will be addressed: (i) To what extent are the two TCs predictable when the associated AEWs were still located over West Africa? (ii) What are the effects of the Saharan Air Layer (SAL), AEWs and convectively generated vortices (CGVs) on Atlantic TC genesis? (iii) What are the processes accounting for the transformation of low-level cold anomalies to a warm-cored vortex? Does TC genesis from AEWs occur from the bottom upward or the top downward? It is hypothesized that (a) AEWs provide the necessary quasi-balanced upward motion for the organization of deep convection and rotation via stretching; (b) TC genesis occurs from bottom up through vortical hot towers, inward potential vorticity flux convergence and upscale growth through CGV mergers; and (c) vertical shear, dry intrusion and convergence of the stable air mass associated with the SAL determine whether or not AEWs could develop to TCs with hurricane intensity. To validate/address the above hypotheses/questions, the Principal Investigator will simulate the TC systems using the Weather Research and Forecast (WRF) model with the finest grid resolution of 1 km. Then, ensemble integrations, initialized with random perturbations or with field observations over West Africa, will be carried out to examine the error growth characteristics and the predictability of TC genesis from AEWs. Diagnostic analyses and budget calculations will be performed to clarify the three-dimensional structures and evolution of the AEWs, and the SAL in relation to the TCs, and to study the upscale growth of CGVs and the thermodynamic transformation. The effects of the SAL, and AEWs on TC genesis will be investigated through sensitivity simulations by modifying their magnitudes and distributions in the model initial conditions with the piecewise potential vorticity inversion technique. Broad impacts: Successful completion of this project will improve understanding and prediction of Atlantic TC genesis from AEWs, particularly the interaction of the SAL with Atlantic storms. Results may benefit the operational 5-day prediction of Atlantic hurricanes, and improve evacuation planning and disaster reduction, thereby facilitating the protection of life and property in the coastal regions. In addition, this project will support graduate education and generate both peer-reviewed journal publications and conference presentations.

智力优点：本研究的目标/任务是（a）对两个与非洲东风波（AEW）有关的热带气旋（TC）案例进行6-7天的云分辨模拟：其中一个发展成飓风，另一个没有;（B）探索这两个风暴的可预报性;以及（c）研究不同环境条件和内部动力学在确定不同TC成因和演变情景中的作用。将讨论以下三个研究问题：（一）当相关的预警武器仍位于西非上空时，两个TC在多大程度上是可预测的？(ii)撒哈拉空气层（SAL）、AEW和对流生成的涡旋（CGV）对大西洋TC生成有什么影响？(iii)低层冷异常转变为暖心涡旋的过程是什么？热带气旋的形成是从底部向上还是从顶部向下？（B）热带气旋自下而上通过涡热塔、向内位涡通量辐合和CGV合并的高增长而形成;与SAL相关的稳定气团的垂直切变、干侵入和辐合决定了AEW能否发展成具有飓风强度的TC。为了验证/解决上述假设/问题，首席研究员将使用天气研究和预报（WRF）模型模拟TC系统，其网格分辨率最高为1公里。然后，合奏集成，初始化与随机扰动或在西非的实地观测，将进行检查的误差增长的特点和可预测性的TC成因从AEW。诊断分析和预算计算将进行澄清的三维结构和演变的AEW，和SAL与TC，并研究高档增长的CGV和热力学转换。SAL和AEW对TC成因的影响将通过敏感性模拟进行研究，通过修改它们的大小和分布在模式的初始条件与分段位涡反演技术。广泛影响：该项目的成功完成将提高对AEW大西洋TC成因的理解和预测，特别是SAL与大西洋风暴的相互作用。结果可能有利于大西洋飓风的业务5天预测，并改善疏散规划和减灾，从而促进沿海地区的生命和财产的保护。此外，该项目将支持研究生教育，并产生同行评审的期刊出版物和会议报告。