The combination of all four factors is illustrated in Figure 12.9. The diagram illustrates the following features:

(a) the pressure-gradient force always acts from high to low pressure regions,

(b) the Coriolis force is always at right-angles to the wind's direction, pulling to the left in the southern hemisphere,

(c) the centrifugal force is also always at right-angles to the wind, pulling outwards,

(d) surface friction involves a complex dissipation of energy in generating turbulent eddies, and the resulting drag normally acts in a direction opposite to that of the wind, and generally increases with wind speed.

Note that Figure 12.9 applies only in steady conditions. In practice, forces fluctuate in space and time. For instance, the pressure gradient along a coast may be reversed by daytime heating of the land. In fact, the surface wind near coastlines and mountains is usually very different from the geostrophic or gradient winds, especially when the latter are weak. Large differences also occur near thunderstorms and jet streaks (Section 12.5).

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Renewable Energy 101

Renewable Energy 101

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. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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