Current Profiles 



Requirements 



27. Since the current data collected by the in situ meters were limited 

 by the available number of meters and the vessel traffic, a current profiling 

 subtask was designed to provide supplementary information. The purpose was to 

 collect vertical current profiles at major entrances and interfaces and within 

 the Cerritos Channel at hourly intervals over half- tidal cycles. The measure- 

 ments were to be made concurrent with deployment of the in situ meters and 

 tide gages. 



28. Figure 5 shows the selected locations of the profile ranges and 

 stations. A range is a transect across an entrance or interface between major 

 sections of the harbor, such as Range 7, and a station is one of three to five 

 locations, depending on width, along a range, for example Station 5D. Sta- 

 tions 9-12 were along the Cerritos Channel and had a single profile, each mid- 

 way across the channel. 



29. A vertical profile consisted of a measurement of current velocity 

 and direction at three depths, near surface, middepth, and near bottom, at 

 each station of a range at 1-hr intervals for 13 continuous hours. 



30. In addition to supplementing the other data, the profiles were ex- 

 pected to identify flow features not readily detectable from stationary meas- 

 urements. A large-scale gyre was observed under certain conditions in the 

 physical and numerical models in the outer Los Angeles Harbor. Range 5 was 

 selected to augment data from a separate Lagrangian current experiment de- 

 signed to verify the existence of the gyre. It entailed continuous tracking 

 of drogues, or floats, that followed the path of the water particles at vari- 

 ous depths. The results of the Lagrangian current study will be presented in 

 a separate report under the Model Enhancement Program. 



31. Stations 9-12 were intended to detect the nodal point for flow 

 convergence of water entering opposite ends of the Cerritos Channel, also as 

 predicted in the model. 



Instruments 



32. The current meter used for profiling was of the same manufacture 

 and general design as the in situ meters, but was equipped with microproces- 

 sors to reduce the data internally into engineering units. The data could be 

 stored onboard in RAM microchips or transmitted over a cable via standard RS 



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