A CONTRIBUTION TO THE THEORY OF UPWELLING. PART 2. THE MOST FAVORABLE CONDITION FOR UPWELLING AND THE COASTAL CURRENTS INDUCED BY WINDS
TEXAS A AND M UNIV COLLEGE STATION
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Consideration is given to upwelling resulting from an offshore wind blowing perpendicular to the coast. Figures are presented to show the streamlines in the vertical circulations induced in the plane perpendicular to the coast by longshore and offshore winds. Both are clockwise circulations, and the stream functions have negative values. A longshore wind appears to originate upwelled water from deeper layers than does an offshore wind. However, the circulation caused by an offshore wind carries a much smaller amount of water than does that caused by a longshore wind of the same stress. The former has a complicated structure with 2 eddies in the upper layers, one situated close to the coast and the other near the outer boundary of the wind belt. Upwelling from a longshore wind is more effective in lowering the surface temperature of the coastal regions than that induced by an offshore wind, because the former carries larger amounts of colder water to the surface from the deeper layers than the latter. An investigation of the most favorable condition for upwelling indicated that the most intense upwelling occurs for a wind making a 21.5 deg angle with the coast line in an offshore direction. A study of the vertical variation of horizontal currents showed that the angle between the wind and surface current is 45 deg at middle part of the wind belt but decreases both toward the coast and outer margin of the wind belt. The vertical variation of currents is practically an Elman spiral along the median of the wind belt, but is somewhat flattened close to the coast and near the outer margin of the belt.
- Physical and Dynamic Oceanography