The Coriolis Effect and Its Contribution to the Formation of Geostrophic Winds

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Geostrophic winds cause cyclones and anti-cylones. The forming of cyclones start when cold air (from the poles or sub-poles) is separated from warm air (from the tropics). Next, in both the upper-level jet and in the surface front, a wave begins to form. The wave grows steadily in amplitude and is baroclinically unstable. Patterns of middle- and high-level precipitation and clouds form the quickly changing trailing warm front and cold front. The frontal zones slope upward on the cold side of their surface positions. In the top part of the troposphere they lay a few hundred kilometres poleward. A temperature gradient will make a sharp boundary between the cold sector air and the warm sector. Warm fronts almost never affect southern Africa; it only affects regions south of Africa. Across the cold front pressure reaches its minimum before rising sharply. The wind swings from south-west to north-west and atmospheric stability drops. Storms may come with the passage of the front, but it might not hit South Africa. There are two types of clouds that should be known according to Tyson & Preston (2012): Ana-fronts, where warm air in the warm sector rises relative to the frontal zone and the fronts are very active, and Kata-fronts, where subsidence of air relative to both the cold air mass and frontal zone less intense and are usually associated inversion. Cold fronts travel more rapidly than warm-fronts. They overtake them to merge in an occluded front. In the next stage the occluded front bends back on itself and comma clouds begins to form. When this occurs the jet stream has secured its most prominent wave-like structure. Afterwards, it decays and the jet has straightened out, collapsing the cyclonic system.

Near or at the Earth’s surface, where the wind encounters obstacles like buildings, trees, topography and slower moving layers of air, frictional drag becomes an added factor because it decreases the wind speed. The pressure gradient will not be affected, but the Coriolis effect reduces at a slower wind speed. If the Coriolis force and the pressure gradient are out of balance, the wind does not flow between the isobars, but instead the surface flows across the isobars into an area of low pressure. If the earth didn’t rotate on its axis, winds wouldn’t blow either east or west. They’d blow from the poles where there’s high pressure, to the equator where there’s low pressure and back again. And if winds didn’t blow east or west, geostrophic winds wouldn’t occur. The Coriolis effect have an impact on the ocean, wind, and other items flowing of flying over the Earth’s surface, which makes the Coriolis effect an important component of the understanding of a lot of physical geography’s most important concepts.

References:

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TYSON, P.D, AND PRESTON-WHYTE, RA. (2012). The Weather and Climate of Southern Africa. Oxford University Press Southern Africa 2000.

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