Circulation of the Wind

Another factor affects any global wind that takes

Figure 12.8 The apparent deflection of a parcel of air moving from a belt of high pressure in the southern hemisphere, e.g. from the band of subtropical high pressures. The parcel is assumed stationary initially. As soon as it starts to move, it suffers a sideways Coriolis force, increasing in proportion to its acceleration. The force deflects the parcel until it is travelling along an isobar, with a constant speed such that the Coriolis force balances the pressure-gradient force.

Figure 12.8 The apparent deflection of a parcel of air moving from a belt of high pressure in the southern hemisphere, e.g. from the band of subtropical high pressures. The parcel is assumed stationary initially. As soon as it starts to move, it suffers a sideways Coriolis force, increasing in proportion to its acceleration. The force deflects the parcel until it is travelling along an isobar, with a constant speed such that the Coriolis force balances the pressure-gradient force.

a circular path. There is then a centrifugal force outwards, the force you experience when driving a car rapidly round a corner. When this also is taken into account, the resultant wind is called the gradient wind (Note 12.D).

The inward and outward forces are shown in Figure 12.9 for the cases of winds circling a high-pressure region (i.e. a 'high' or 'anticyclone') and a low-pressure region (i.e. a 'low' or 'cyclone'). The Coriolis force on air which is moving around a high is matched by the pressure-gradient force plus the centrifugal force. This necessitates a larger Coriolis force than in the case of a geostrophic wind (where the centrifugal force is zero). Such a larger force requires a faster wind speed, since the Coriolis force is proportional to the speed (Note 11.D). In other words, the wind around a high is supergeostrophic. Similar reasoning shows that the wind around a low is trophic. In every case,

Supergeostrophic Winds
Figure 12.9 The forces involved in winds around (a) a high, and (b) a low. Also, (c) the forces acting on winds near the surface when the isobars are straight and friction retards the flow.

winds go faster around a high than around a low for a particular pressure gradient (Note 12.D).

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Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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