A pilot project was completed in the San Francisco Bay from May 1-10, 2009 (continued in SF Bay Web part II), to demonstrate the feasibility of using advanced moorings combined with undersea and wireless networking to move environmental data to the internet in real-time. The project was collaborative across universities and state and federal agencies and was hosted by SFSU's Romberg Tiburon Center (RTC) in Tiburon, CA. A new integrated system provided by the Naval Postgraduate School was used to sample the current profiles and transmit the data to shore in real time via an air/sea communications network. The current profiler, acoustic release, and acoustic modem were all housed in a hydrodynamic syntactic float designed by Flotation Technologies Inc. The data were transmitted to shore via a communication gateway mounted on a USCG navigation buoy. Many thanks to the USCG for recovering and re-deploying the buoy. Ship surveys were also completed by UC Berkeley, the Bodega Marine Lab, and RTC to help understand the observed circulation.
The long-term plan is to make such information available all the time, and use it to constrain the new community model of the bay circulation being developed by UC Berkeley and Stanford. The model output will in turn be used to address community needs in the areas of maritime safety, water quality, spill containment, and ecosystem health.
This website reports some first-look results from the project. It includes a locator map, data plots, photos of operations, a short video of a mooring recovery and a slide show with some additional information including a list of collaborators.
Powerpoint presentation of San Francisco Bay Web project
San Francisco Bay Web Map
Figure 1. A locator map showing the two moorings, gateway buoy, and bottom repeater nodes. Site ADCP 1 is referred to subsequently as "Raccoon Strait" and ADCP 2 as the "Main Channel".
Figure 2. Pressure fluctuations observed by the two instruments. The dominant signal is the semidiurnal tide. These fluctuations are a combination of mooring motion due to tidal currents and actual rise and fall of the sea surface due to the tides. Note the increasing tidal amplitude towards the full moon on May 9.
Figure 3. Temperature at Raccoon Strait (red) and the Main Channel (blue). The coldest water appeared at the end of the flood tide, and vice-versa.
Main Channel Currents
Figure 4. The east/west (top) and north/south (bottom) current components from the Main Channel. The flood tide is towards the northeast and the ebb tide is towards the southwest. The tidal currents were nearly uniform vertically in the east/west direction but not in the north/south direction. At the beginning of each ebb (southward) tide, an unusual shear structure appeared when the flow was still northward at the surface but southward at the bottom. The current then became southward throughout the water column until the tide turned to flood once again.
ADCP 1's Compass failed to work, so currents from it are not plotted
Figure 5. A different presentation of the currents in the Main Channel. The east/west component of the flow for all depths (in 2 m bins) is shown in the top panel, and the north/south component in the lower panel. The lines usually track one another, indicating uniform flow from top to bottom. Sometimes however the lines diverge in the north/south component, indicating a flow that is quite different from top to bottom.
Figure 6. Current vectors for the north/south component of the current in the Main Channel near the surface (5 m, top panel) and near the bottom (30 m, bottom panel) highlighting the times when the surface and bottom currents were opposed. The scale indicates the strength of the current. Upward-pointing lines are northward (flood tide) and downward-pointing lines are southward (ebb tide). The ebb/flood pattern is much clearer at the bottom than at the surface. This regular pattern of opposing currents occurred at the beginning of each ebb tide.
80 Mb Quicktime movie of the current profile
Figure 7. Mooring performance: Plots of pitch (top) and roll (bottom) for the Raccoon Strait (red) and Main Channel (blue) moorings. Both should be zero at slack water, but had offsets indicating they were not balanced correctly. Both pitch and roll fluctuated by about 4 degrees, which is very good for a short mooring and high currents. None of the angles are severe enough to impact current profiler performance.
QuickTime movie of the StableMoor surfacing courtesy of Bob Creber
Google Earth KML file of ADCP2 data
View an animation of the currents observed at ADCP2. This instrument and mooring were provided by the Naval Postgraduate School. The communications network used to transmit the data to shore was a collaboration between the Navy and the U.S. Coast Guard. [You will need Google Earth with terrain on. Use the wrench tool to adjust the speed.]DATA LINKS
NOTE: ADCP 1's compass failed to work. All velocity component data are unusable as is. The raw data files require the use of WaveMon3 from Teledyne RDI to read properly.An explanation of the Matlab file variables used can be found here.
ADCP 1 was located at 37 51.499' 122W 27.315' in 35 m of water, times are LOCAL!
- ADCP 1 raw data file (use WaveMon3 from RDI to read/process)
- ADCP 1 processed currents (matlab file)
- ADCP 1 scalar data (matlab file)
ADCP 2 was located at 37N 50.488' 122W 25.281' in 39 m of water, times are LOCAL.
- ADCP 2 raw data file (use WaveMon3 from RDI to read/process)
- ADCP 2 processed currents (matlab file)
- ADCP 2 scalar data (matlab file)
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