IZE 81 PROFILE 



IF LAYER DEEPENS^ SET AVERAGE 

 VELOCITIES FROM UO TO Z=DNEW 





NO 





APPLY KEAI 



EauJiiONS 







1 ' '" «'"""" """ 





1 YES 









«Y 3-2 





* 









Figure 3.1 Flowchart of the Model Computational Scheme. 



T was solved for in all time steps, whether the 

 mode of the model was heat or wind driven. Any 

 penetration of solar radiation such that water 

 below the mixed layer is warmed is accounted for 

 by 2.4. 



Because of the nature of the deepening cycles, 

 and the possibility of the formation of a shallower 

 mixed layer by heating (Figure 2.1), it becomes 

 necessary to consider the effect of a layer of water 

 near the surface, bounded by a temporary ther- 

 mocline, deepening into a water layer already set 

 into motion by a previous wind event. Since the 

 entrained water already has momentum, some 

 account of this momentum must be made. Since 

 there is rapid mixing throughout the wind forced 

 layer, this "entrained momentum" can be ac- 

 counted for in a similar manner as was the 

 temperature. Therefore, before each time step of 

 current computations, an average velocity is 

 taken over the entire deepened layer. (Pollard, 

 Rhines and Thompson, 1973) 



A time step of 900 seconds was used throughout 

 the model to minimize the amount of error in the 



numerical solution and to more clearly differen- 

 tiate the time where the Denman equations 

 transfer from the wind forced to the heat driven 

 modes. The entire computation scheme is illus- 

 trated in the flowchart of Figure 3.1. 



Figure 3.2 shows a result of the model illustrat- 

 ing the possibility of velocity shears and changes 

 in mixed layer thickness. This is a part of the run 

 testing the mixed layer deepening section of the 

 program. At time = 146 hours, three different 

 velocity fields are seen. From the surface to 19.9 

 meters is seen the mixed layer and currents pro- 

 duced by the current wind event. The values at 20 

 meters are for a wind event earlier than the cur- 

 rent one that produced mixed layers to a depth of 

 20 to 25 meters. A third wind event, the first 

 chronologically, produced the strong, decaying 

 velocities between 25 and 40 meters. This earliest 

 wind event produced a mixed layer between 40 

 and 45 meters deep. One hour later, it is seen how 

 the wind forced water entrains the fluid beneath 

 it, while the lower layers continue unforced. 



