4. THE CHARACTERISTIC COMPONENT 



The characteristic component is directly related to density 

 gradients caused by areal differences in heating-cooling and 

 evaporation-precipitation. Although what we usually call "the 

 permanent flow" is strongly controlled by the large-scale, more- 

 or-less stationary wind systems, only the thermo-haline influences 

 are included in that component here . Vvind and wave effects will 

 be lumped into one computation to be discussed later. 



Several workers have found (e.g. Yasui 1957) that there is a 

 close correlation between ocean temperature distribution and 

 dynamic depth anomalies. Neglecting salinity, one can apply 

 the well-knovvn meteorological thermal wind relationship in the 

 ocean if one knows the mean temperature of the layer between the 

 surface and some level of zero current velocity. The characteristic 



current is then given by: 



gAz _ 

 W^ = ;37- VT X IK (2) 



C J rj, 



where g is gravitational acceleration, f is the Coriolis parameter, 

 T is the mean temperature above the level of zero current, Az 

 is the depth to zero current, and |K is the unit vertical sector. 



