Laboratory Simulation of Mechanical Effects of Mountains on the General Circulation of the Northern Hemisphere: Uniform Shear Background Flow

Abstract

Abstract The dimensionless governing equations and boundary conditions for the atmosphere are compared with those for a linearly stratified rotating dishpan laboratory experiment; by doing so a set of similarity criteria are determined. Model experiments on the effects of Greenland, the Rocky Mountains and Tibet on a uniform shear zonal flow in the Northern Hemisphere are presented. The laboratory model qualitatively simulates such semipermanent features of the Northern Hemisphere circulation as the Aleutian and Icelandic lows, the ridgesand troughs in the vicinity of the Rocky Mountains and Tibet and the shedding of the southwest eddy in the lee of Tibet. Although the background flow is steady, the large-scale disturbances caused by the mountains are unsteady and have an inherent periodicity equal to the time required for a fluid parcel to make a single 'circuit around the dishpan (globe). The strengths of the Aleutian and Icelandic lows, for example, oscillate with this Iiod; the lows are out of phase...