THERMAL STRUCTURE PREDICTION 



The Navy needs to predict therm- 

 ocline depth and strength to make efficient 

 use of sonar equipment. Tower studies 

 have established that these predictions can 

 be successfully made in the summer 

 months by using wind speed and direction 

 and tide height data. 



The interrelationships between 

 wind, tide, and thermocline were estab- 

 lished by continuously recording these 

 parameters throughout one summer. From 

 this study, empirical equations have been 

 developed. It was established that the 

 nearly semidiurnal tide height is of pri- 

 mary importance and that the diurnal wind 

 speed and direction (nearly parallel to the 

 coast in accordance with the Ekman effect) 

 is of secondary importance. Since the 

 thermocline response is 4 hours later for 

 tide and 15 hours for wind, it is possible 

 to predict in advance the thermocline 

 change at the tower within accuracies of 

 practical limits. 



The thermocline goes through 

 cyclic variations in strength that corre- 

 spond with the tide. The descending 

 thermocline is stronger than the ascending 

 one. The temperature gradient in descent 

 is approximately 0. 3 degree C/ft, and in 

 ascent it is approximately 0.1 degree C/ft. 



Diurnal cycles in sea breezes normally cause a 

 shoreward (left) and offshoreward (right) displacement 

 of surface water, in accordance with the Ekman 

 effect. The surface-water displacement is such that 

 the thermocline reaches a maximum depth about 1800 

 hours and a minimum depth in the early morning. Such 

 fluctuations in the thermocline level may amount to 

 as much as 30 feet in 2 hours. 



WIND 



30 



