This term is applied to winds that occur between polar high pressure and subpolar low pressure. The polar high, as has already been pointed out, is by no means a quasi-permanent feature of the Arctic circulation. Easterly winds occur mainly on the poleward sides of depressions over the North Atlantic and North Pacific (Figure 7.12). If average wind directions are calculated for entire high-latitude belts there is found to be little sign of a coherent system of polar easterlies. The situation in high latitudes of the southern hemisphere is complicated by the presence of Antarctica, but anticyclones appear to be frequent over the high plateau of eastern Antarctica, and easterly winds prevail over the Indian Ocean sector of the Antarctic coastline. For example, in 1902 to 1903 the expedition ship Gauss, at 66°S, 90°E, observed winds between northeast and south-east for 70 per cent of the time, and at many coastal stations the constancy of easterlies may be compared with that of the trades. However, westerly components predominate over the seas off west Antarctica.
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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.