The Tropospheric Circulation 655 



The upwelling velocity will be proportional to the intensity of the northerly wind but 

 is not directly dependent on the latitude. When g* = g{Apjp) — 2-5, i/ = 40 m = 

 4 X 10^ cm and Ty,Q = —0-5 then 



H'a-^o = — 5 X 10"^ cm sec ~^. 



In five days this upwelling will give an upward displacement of the thermoline of 

 22 m. This upward movement of the thermocline off the coast will continue until an 

 equilibrium is reached in about a week and according to observations seems then to 

 be maintained for about one or two months. The region where this coastal upwelling 

 occurs is confined almost entirely within a narrow strip close to the coast. With the 

 numerical values introduced above, k will result to '^0-7 X 10~^ cm~^; at a distance 

 of 40 km, w will be reduced to 6% of that at the coast and to only 3% of the coastal 

 H-value at 50 km. The process is practically limited to a distance of 40-50 km from the 

 coast. The effective width of coastal upwelling is given by a characteristic length 



Yoshida also investigated the changes in surface conditions which were derived 

 from the above model of a transient state of upwelhng. He found that the variations in 

 surface characteristics were largely confined within the narrow coastal regions. The 

 coastal upwelling is associated with considerable changes in surface conditions within 

 the coastal waters of width L, while upwelling or sinking outside this strip will not give 

 rise to such significant changes during a period of only a week or two. In the succeeding 

 stage of the upwelling process, in which now the isostatic adjustment can be con- 

 sidered a complete one, the laterial mixing process in the inshore regions stands out as 

 the most important factor. The dynamic equations are now 



- A- = - I , (XIX.69) 



ft^ = ^ + A,-^„ (XIX.70) 



where A,, is the coefficient of lateral mixing. The upward movement of the thermoline, 

 due to the ascending motions, will produce a sharp horizontal density gradient and 

 when conditions are variable in an oscillatory way, as is usually the case, internal 

 waves will originate and cause intense mixing across the thermocline. The equation 

 for the conservation of mass will now become 



or, approximately 



w ^ - An 



dx" 



The boundary condition at the coast gives Tq = so that finally 



^^ = -g-dx' ^^^^-^^^ 



