A Numerical Simulation of the Effect of Relief on Atmospheric Circulation

In this paper, a barotropic primitive equations model in the Northern Hemisphere and ideal initial field are used. The altitude of the smooth relief is considered in the model. The equations are integrated through 240 hours for some wave systems in which the wave numbers are 2, 3 (ultra–long wave), 4 and 5 (long wave), respectively. Comparing these solutions with those obtained from the model in which the altitude of the relief is not considered. Four pairs of the solutions show that the effect of the altitude on the evolution of the four sorts of wave types is very obvious. It is confirmed that the effect of the relief on the general circulation and some characteristics of weather types is really one of the key factors. It is also found that some main patterns of atmospheric circulation in the Northern Hemisphere are formed due to the dynamical effect of the relief. For example, the movement of the arctic vortex to North Europe, the maintained troughs over East Asia and North America, and the maintained ridge over Alaska are closely related to the relief. In this model, the effects of the relief present: A trough is in the west and a ridge is in the east of the North Pacific, while a ridge is in the west and a trough is in the east of North Atlantic. The presences of blocking highs and cut–off lows are more frequent and more typical. As m=4, the flow pattern looks like a upside–down Ω, while m=5, the flow pattern is trough–ridge–trough over the continent of Europe and Asia