US-Austria Cooperative Research: Evaluating Sensible Heat Flux Density above Smooth and Rough Vegetation

该奖项支持亚利桑那大学的Lloyd W.Gay教授与维也纳农业大学气象、气候学和应用物理研究所的Inge Dirmhirn教授合作进行研究。他们研究的目标是改进测量地球表面和大气之间热能自然转移的技术，从而提高我们对控制这种热转移的过程的理解。部分挑战是，在平坦的地形上工作得相当好的技术，在森林等更粗糙的环境中并不能提供可靠的结果。他们将在两个地点使用三种不同的方法评估显热通量，这两个地点提供了对比的空气动力学粗糙度。他们的研究地点将是亚利桑那州一个统一、相对平滑的农业地点，以及奥地利一个更粗糙的橡树森林地点(Hochleitenwald)，奥地利人在那里建造了一座高塔，用于在19米高的森林表面进行研究。合作者还为这项研究带来了方法论上的互补优势，因为盖伊博士是鲍文比方法方面的专家，奥地利人在涡旋关联方面非常有经验；两个小组都有空气动力学模型的经验，这是他们将使用的第三项技术。地表和大气之间的动量、能量和质量交换对影响人类的各种环境现象极其重要。努力将我们关于气象、水文和生态过程的知识从地方扩展到全球，需要改进评估这些交流的工具。用于表面交换的相当复杂的波文比和涡旋相关技术是目前选择的方法。然而，从空气和空间遥感传感器对表面交换的解释重新引起了人们对简单的空气动力学交换模型的兴趣，尽管这些模型的早期承诺在应用于更粗糙的表面时并不是很好。拟议的实验借鉴了过去十年在仪器和实验技术方面的重大进展，将加深我们对表面交换过程的理解，并为将交换模型应用于空气动力学粗糙、复杂表面提供指导。

This award supports Professor Lloyd W. Gay of the University of Arizona to collaborate in research with Professor Inge Dirmhirn of the Institute of Meteorology, Climatology and Applied Physics, Agricultural University of Vienna. The goal of their research is to improve the techniques for measuring the natural transfer of thermal energy between the surface of the earth and the atmosphere, and, thereby, to improve our understanding of the processes that control this transfer of heat. Part of the challenge is that techniques which work reasonably well on smooth landscapes do not provide reliable results over rougher environments such as forests. They will evaluate sensible heat flux using three different methods at two locations that offer contrasting aerodynamic roughness. Their research sites will be a uniform, relatively smooth agricultural site in Arizona, and a rougher oak forest site (the Hochleitenwald) in Austria, where the Austrians have built an elevated tower for research on the surface of that 19 meter-high forest. The collaborators bring to the research complementary strengths in methodology as well, since Dr. Gay is an expert in the Bowen ratio method and the Austrians are very experienced in eddy correlation; both groups have experience with aerodynamic models, which is the third technique they will use. The exchange of momentum, energy and mass between the surface and the atmosphere is extremely important to a variety of environmental phenomena that affect humans. Efforts to expand our knowledge of meteorological, hydrological and ecological processes from local to global scale require improved tools for evaluating these exchanges. The rather complex Bowen ratio and eddy correlation techniques for surface exchange are currently the methods of choice. However, interpretation of surface exchange from air and space-based remote sensors has generated renewed interest in simple, aerodynamic exchange models, even though early promise of these models did not hold up well in applications to rougher surfaces. The proposed experiments, drawing upon the substantial advances in instrumentation and experimental techniques of the past decade, will refine our understanding of surface exchange processes, and provide guidance for application of exchange models to aerodynamically rough, complex surfaces.