Laboratory simulations of atmospheric dynamics in the rotating fluid annulus experiments.

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In the recent ten years it has become gradualy acknowledged to be fundamentarlly importent in fluid dynamics, meteorological and oceanographical problems to investigate Lagrangian motions in fluids. Only a few such experimental studies, however, have veen so far done. In this project we have developed experimental method to observe 3-D Lagrangian trajectories in the rotating fluid annulus which is designed to produce baroclinic waves found in the large scale circulation of the atmosphere in the mid-latitud of the earth. Neutrally buoyant tracer particles are made from fluorescent matter and illuminated by ultraviolet light in the dark room to detect their position by two videocameras. There our early developed apparatus of double rotating turn-tables was used to track a tracer particle. In the first year (1995) of this project we developed the method to make tracer particles that are buoyant for a long time. Thus, we succeeded in obtaining the data of the particle trajectories for the … More total time of more than ten hours. The result has been reported at Physical Society of Japan, Meteorological Society of Japan, Fluid Dynamics Society of Japan and Visualization Society. The paper which describes these experiments will be soon published. New discovery in our experiments is a significant difference of the Lagrangian motions between the wavenumber-4 and 5 wave. This is very important in the meteorological studies because it suggest that the mechanism of the heat transport is different between the wavenumbers. Though a part of our experimental result is consistent with the result of the numerical simulation done by Sugata and Yoden, our data were insufficient for getting the reliable conclution. We realized neccesity of performing more than 10 hours tracking in one experiment. In the second year (1996) of this project we developed a system of tracking a tracer particle automatically with a personal comuter in order to make it very easy to perform long term trackings (for more than 10 hours). Furthermore we made microcapsuls of ultraviolet luminous dye as tracer particles with the cooporation of Threetech Debys Co. and tested them in experiments so that they were proved to be very suitable for tracers. We have a plan to carry out future experiments after reinvestigating the physical conditions. Less