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

迄今为止，人们对平流层中的空气运动进行了理论和数值模拟研究。然而，实验室模拟对于研究它们的基本动力学结构也很有用。本项目的目的是在旋转的流体环上进行实验，研究斜压流向上传播进入上层层，并在平流层中产生类似极地涡的紧密闭合涡。利用水深13-14 cm的环空，通过加热水面，成功地在下层产生斜压流，施加3 cm以下的径向温差，使上层5 cm以上分层。在本科研项目中，我们得到了以下两个实验结果：【圈1】根据大气动力学中的准地转位涡方程，塔架流体层产生的正压波涡度穿透分层上层，随高度呈指数衰减；【圈2】如果层状层足够深，则需要强的层状（垂直温度梯度）才能在斜压下层出现稳定的轴对称流或波状流。将结果应用到实际大气中，特别是臭氧层吸收紫外线并使空气变暖从而形成平流层，对于中纬度大尺度对流层风是必不可少的。这一结果在《流体实验》杂志上发表的一篇论文中得到了描述。这一结果已在提交给《大气科学杂志》的论文中进行了总结。

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.