9424201 Emanuel Dr. Emanuel will continue to investigate several aspects of the reasons for the development and evolution of tropical cyclones. The first part of the research effort will be to complete the analyses of data taken during the Tropical Experiment in Mexico (TEXMEX). When completed, the development of four hurricanes will have been analyzed from the data and simple numerical simulations of the cases completed to test the physical hypotheses formed to explain the observations. In a separate investigation, the PI will test his hypothesis that spiral bands in hurricanes are squall lines whose orientation with respect to the hurricane's vertical shear at each point is determined by the interaction of the mean shear with the dynamics of the cold pool of air found near the surface in hurricanes. This will be tested using a three- dimensional ensemble model. Finally, the PI will begin a study on the concentric eyewalls that are observed in hurricanes, seeking through numerical studies to test his hypothesis that the cycles of the eyewalls are a form of wind-induced surface heat exchange instability of the mature hurricane circulation. All of these efforts are important in improving our understanding of the behavior of tropical cyclones. This award is jointly supported by the Mesoscale and Large-scale Dynamic Meteorology Programs. ***
