Mesoscale Air-Sea Coupling in Tropical Cyclones Isidore and Lili

这项研究的长期目标是增进对中尺度海洋过程如何通过海-气相互作用改变热带气旋近地面风结构的理解。尤其重要的是当热带气旋经过美国大西洋和墨西哥湾海岸外温暖的海洋地貌时发生的相互作用。了解低边界效应不仅从研究角度具有重要意义，而且对于预报登陆风暴的地面风场和强度变化也具有深远的影响。主要研究主题是热带气旋遇到中尺度海洋特征时，海洋垂直混合和平流对大气边界层(ABL)中热量、水汽和动量通量的物理影响。具体的研究目标是：1.利用现场和卫星派生的场改进风暴前后的海洋热含量估算(OHC)。研究了暖海洋特征对嵌入在直接强迫区域内的ABL中增强的表面应力、通量和表面波的强迫作用，以及海洋混合层(OML)反馈对ABL.3的作用。通过分析质量、热量和盐分的混合和水平平流在OML中的收支，特别是降水的影响，来量化它们的作用。记录大气环境中的变异性，例如相对于风暴和上层海洋变化性的等效位温和风切变。在飓风伊西多尔和莉莉(2002年)期间，首席调查员和合作者能够在强飓风强迫条件下收集迄今最全面的海洋大气数据集之一。这些观测包括测量上层洋流、温度和盐度分布，以及同时测量大气温度、湿度和风向分布。此外，使用美国国家海洋和大气管理局的一架研究飞机释放的数百个大气探测仪观测到了大范围的大气变异性。为实现研究目标，首席调查员将利用上述数据和混合坐标海洋模式，采用观测和数值相结合的方法。这项研究的一个重要方面将是开发一套一致的度量标准，以评估海洋模式在模拟上层海洋对TC强迫的响应方面的性能。这项研究的成功完成最终可能导致预报模型的改进，从而可能导致对热带气旋强度的更好预报。

The long-term goal of this research is to improve understanding of how mesoscale ocean processes modify the near surface wind structure of tropical cyclones through air sea interactions. Of particular importance are the interactions occurring as tropical cyclones pass over warm oceanic features off the Atlantic and Gulf coasts of the United States. Understanding lower boundary effects is not only important from a research perspective, but also has far reaching consequences with respect to forecasting the surface wind field and intensity changes for landfalling storms. The main research theme involves the physical effects of oceanic vertical mixing and advection on heat, moisture, and momentum fluxes in the atmospheric boundary layer (ABL) as tropical cyclones encounter mesoscale ocean features. Specific research objectives are:1. Improve pre and post storm ocean heat content estimates (OHC) using in situ and satellite derived fields.2. Examine the forcing by warm ocean features on enhanced surfaces stresses, fluxes and surface waves in the ABL embedded within the direct forcing region, and the role of the ocean mixed layer (OML) feedback on the ABL.3. Quantify the roles of mixing and horizontal advection of mass, heat, and salt by analyzing their budgets in the OML, focusing especially on the effects of precipitation.4. Document the variability in the atmospheric environment such as equivalent potential temperature and wind shear relative to the storm and upper ocean variability.During Hurricane Isidore and Lili (in 2002), the Principal Investigator and collaborators were able to collect one of the most comprehensive ocean atmosphere data sets to date under strong hurricane forcing conditions. These observations included measurements of upper ocean current, temperature and salinity profiles along with simultaneous atmospheric temperature, moisture and wind profiles. Additionally, the large scale atmospheric variability was observed using several hundred atmospheric sondes released from a research aircraft from the National Oceanic and Atmospheric Administration. To achieve the research objectives, the Principal Investigator will utilize a combined observational and numerical approach using the aforementioned data and the HYbrid Coordinate Ocean Model (HYCOM). An important aspect of this research will be to develop a set of consistent metrics in order to assess the performance of the ocean model in simulating the upper ocean response to TC forcing. Successful completion of this research eventually could lead to improvements in forecast models that could lead to better intensity forecasts for tropical cyclones.