Abstract: In our experiment, the fluid is contained between two concentric rotating didhpans, the inner one is a cold source and the outer a heat source. The increase and secrease of the temperature difference between the heat and cold source may effect the changes of the wave number of fluid flow in a steady rotating dishpans. It is analysed carefully that the four-waves flow changes into three-waves and vice versa. We observe that the mean meridional circulation and the intensity of mean zonal current vary rapidly during the changes from the four-waves flow into three- waves. In the steady four-waves flow, the mean meridional circulation is indirect, with a descending motion near the cold source and an ascending motion near the heat source, as shown in Fig. 4.However, at the beginning of the transformation from the four-waves flow into three-waves, the mean meridional circulation changes rapidly into direct (Fig. 4).As soon as the three-waves flow has been formed, the indirect mean meridional circulation is reproduced. The mean zonal flow is also changed with the mean meridional circulation. At beginning it intensifies and then it weakens. During the transformation from three-waves flow into four-waves, the variations described above in mean meridional circulation and zonal flow do not occur, but the variations in intensity may also appear. It is calculated that the heat transfer by large-scale eddies is different between three-waves and four-waves steady current. The heat transfer by eddies of three-waves is larger than that of four-waves. Some explanations of these results of the experiment are discussed. It seems that the variations of meridional circulation and heat transfer by large-scale eddies may play an important role in the medium range variations of the general circulation of the atmosphere.