Global Air Circulation

Because Earth does rotate, however, another set of forces also acts on the fluids these geostrophic forces are the consequence of the fact that Earth s surface forms an accelerating reference frame. Relative to Earth s surface, all fluid motions are deflected perpendicular to their velocity by the Coriolis force in the Northern Hemisphere, fluid motions are deflected to the right, and in the Southern Hemisphere, to the left. A parcel of fluid in motion in the Northern Hemisphere, under the influence of only the Coriolis force, experiences acceleration equal to 

FIGURE 4-11 Global-scale tropospheric circulation as it would be if Earth did not rotate. Heat is transported from the equatorial area to the cold polar regions by both atmospheric and oceanic currents in each hemisphere. 

The Coriolis force, in conjunction with solar heating, creates a more complex global circulation pattern than that shown in Fig. 4-11. Three major latitudinal bands of surface winds result from these combined forces. In the Northern Hemisphere, the trade winds lie between the equator and approximately 30° latitude and are generally from the northeast (Fig. 4-13). North of the trade wind latitudes, between approximately 30° and 60° latitude, pole-ward-moving surface winds are deflected to the right by the Coriolis force, giving rise to the westerlies. Finally, from approximately 60° poleward, a third global-scale convective flow moves southward near Earth s surface and returns 

No velocity v (relative to disk) Absolute tangential velocity =bi Centripetal force = (m(cjr)8)/r Centripetal force supplied by fluid 

Power Iobb to centripetal force = muzrv Power input from F = Fwr Power input = power loss + dKE/dt Fur = mw8ru + mu8rv F/m = 2av 

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