OpenUCT :: Browsing by Author "Boyd, Alan John"

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An intensive study of the currents and general hydrology of an anomalous upwelling area off South West Africa
(1981) Boyd, Alan John; Brundrit, Geoff
The currents, winds and hydrology of a coastal site of approximately 120 square miles off South West Africa were studied intensively for two weeks during June/July 1978. Currents were measured by means of drogues tracked by RADAR from a central station at 45m of water depth. Classical inertial motion was observed at several depths during a calm period implying a short relaxation time for pressure gradient forces and the existence of different Velocity layers within the water column. Diurnal sea breezes and landbreezes controlled the currents at 2 and 5m depth with a response time of a few hours but the deeper currents were not directly affected by wind. Average surface current speeds were between 0,2 and 0,3 kts. Sustained southerly winds caused a deepending of the upper layer and were accompanied ~y slower currehts. Selected data recorded during the diurnal wind regime yielded the relationship: Surface current speed = 0,017 x Windspeed. A meandering poleward under-current with an average velocity of 0,07 kts was detected at 30m depth whilst onshore flow of similar average speed existed at 20m. Using the results of the experimental work as a basis, the upper layer of the sea to 8m depth was modelled as a slab, which was affected by wind, friction and the coriolis force.