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.
