Flying The Big Jets (4th Edition) by Stewart Stanley

Flying The Big Jets (4th Edition) by Stewart Stanley

Author:Stewart, Stanley [Stewart, Stanley]
Language: eng
Format: azw3
ISBN: 9781847979216
Publisher: Crowood
Published: 2014-09-29T16:00:00+00:00


Fig. 8.2 Average surface pressures, worldwide, in January and July.

Air on the surface flows from regions of high pressure to regions of low pressure. Since the areas are generally well defined, it is not difficult to construct an idealised diagram (Fig. 8.3) showing the distribution of pressure and wind and the general circulation of upper air currents throughout the world, although in reality the situation is more complex. Air does not flow directly from high to low pressure areas because of the spinning earth (the Coriolis effect), which results in winds being deflected to the right in the northern hemisphere and to the left in the southern hemisphere. In the northern hemisphere (Fig. 8.4), low pressure areas have a cyclonic motion consisting of a circular wind movement rotating in an anticlockwise direction, and in high pressure areas an anticyclonic motion rotating in a clockwise direction, and vice versa in the southern hemisphere. High pressure areas, therefore, are frequently referred to as anticyclones, but low pressure areas are more commonly referred to as depressions. In some tropical regions revolving storms resulting from intense depressions are known as cyclones, but also as hurricanes and typhoons, depending on the area. Localised depressions with strong cyclonic winds are frequent in the United States and are known as tornadoes.



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