Rotating annulus experiments to simulate the air motion in the stratified layer

点击翻译按钮获取中文摘要

The air motions in the stratosphere have been so far studied theoretically and by numerical simulations. Laboratory simulations are, however, also useful to investigate their basic dynamical structures. The purpose of this project is to conduct experiments on a rotating fluid annulus to study the upward propagations of the baroclinic flows into the upper stratified layer and to produce the tightly closed vortex such as the polar one in the stratosphere. Using the annulus whose water depth is 13-14 cm, we have succeeded in producing the baroclinic flows in the lower layer imposed the radial temperature difference below 3 cm and making the upper layer above 5 cm stratified by heating the water surface. In this research project, Grant-IN-Aid far Scientific Research, we have gotten the following two experimental results : 【encircled 1】The vorticities of barodinic waves produced in the tower fluid layer penetrate into the stratified upper layer decaying exponentially with height according to the quasi-geostrophic potential vorticity equation in the atmospheric dynamics ; 【encircled 2】If the stratified layer is sufficiently deep, strong stratification (vertical temperature gradient) is necessary for steady axisymmetric or wave flows to emerge in the baroclinic lower layer. Applying the result 【encircled 1】to the real atmosphere, in particular, that the ozone layer absorbs the ultraviolet light and warm up the air to make the stratosphere is found essential for the mid-latitude large-scale tropospheric winds. The result 【encircled 1】 was described in the paper that was accepted for the publication in Experiments in Fluids. The result 【encircled 1】 has been summarized in the paper submitted to Journal of Atmospheric Sciences.