URANIUM SERIES 



upward irradiance — The radiant flux incident 

 on iin infinitesimal element of the lower face 

 ( 180 to 360 degrees) of a horizontal surface con- 

 taining the point being considered, divided by 

 the area of tliat element. Unit of measurement 

 is watt per square meter (W/m^) . (8) 



upwelling — The process by which water rises from 

 a lower to a higher depth, usually as a result of 

 divergence and offshore currents. See sinking. 

 Upwelling is most prominent where persistent 

 wind blows parallel to a coastline so that the re- 

 sultant wind-driven current sets away from the 

 coast. See Ekman spiral. It constitutes a dis- 



tinct climatogenetic influence by bringing colder 

 water to the surface. Over the open ocean, up- 

 welling occurs wherever the wind circulation is 

 cyclonic, but is appreciable only in areas where 

 that circulation is relatively permanent. It is 

 also observable when the southern trade winds 

 cross the Equator. 



The upwelled water, besides being cooler, is 

 richer in plant nutrients, so that regions of up- 

 welling are generally also regions of rich fish- 

 eries. (5) 

 uranium series — The series of nuclides resulting 

 from the decay of U^'*. (41) 



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