CMO SuperBASS Deployments

A.J.Williams, John H. Trowbridge, George Voulgaris
William Shaw, J.J.Fredericks
** page under construction (not reviewed) **
(data links and plots not implemented)

A large tripod (SuperBASS tripod) was deployed as part of the Coastal Mixing & Optics Programs near the central mooring site off the coast of New England (Figure 1). The SuperBASS tripod was equipped with both BASS and Sontek ADV velocity sensors, as well as instrumentation to observe temperature, salinity, pressure, pitch, roll and heading. Five deployments provided data between August of 1996 and August of 1997. The location of each deployment, relative to the surface discus buoy at the central mooring site, is shown in Figure 2.

Three ADV sensors were mounted along each bottom-channel. These provided simultaneous records of horizontal and vertical velocity components at each sensor location. (See tripod orientation.) BASS velocity and acoustic travel-time sensors were stacked between 0.4 mab and 7 mab. Temperature, salinity Seabird pairs were mounted at the bottom-most and top-most BASS sensor elevations, along a leg. The pressure and orientation sensors were placed on the pressure case platform (4.2 mab). For Deployments IV & V, a string of 8 thermistors were placed next to the BASS pods.

There were two logging systems used to record the data. One system recorded the three ADVs on three loggers at 25Hz in nine minute bursts every hour. Another logger recorded the BASS velocity, along with the other environmental variables, at 1.2 Hz in three 29 minute bursts every other hour.

Overview plots of BASS velocity, temperature, salinity and depth are available for each deployment.

Deployment I: 8/18/96 - 9/27/96

3 - ADV velocity sets at 0.35 meters above bottom (through 9/1/96)
7 - BASS (ACM) velocity sets at (0.4, 0.7, 1.1, 2.2, 3.3, 5.4 & 7mab)
7 - BASS travel-time sets at BASS ACM heights
2 - SeaBird temp, salinity sensors (0.4 & 7mab)
1 - ParoScientific pressure records (4.2mab)
1 - Compass, pitch & roll

Two hurricanes passed over the deployment site. Due to power supply failure, the ADV system failed on 9/1/96. Upon recovery, it was found that support cabling had corroded and broken away from the BASS central tower, which had to be rebuilt before the second deployment.

Deployment II: 10/7/96 - 12/27/96

(Same configuration as Deployment I)

 Upon recovery of the tripod (1/5/97), it could be seen that the whole structure was covered with 1-2 cm of 'furry' growth. Both the ADV and BASS velocity and acoustic travel-time systems worked throughout the deployment, although after mid-November the data are spikey and standard deviations of the ADVs are high. Also, due to disk i/o problems, there are periods when some of the bursts were truncated or split into two or more separate bursts. For reasons not fully understood, the pressure and SeaBird data failed after 10/16.

Deployment III: 1/97 - 4/9/97

 3 - ADV velocity sets at 0.35 meters above bottom

ADV records were oriented using comparisons with simultaneously sampled moored data (S. Anderson). This was necessary because the BASS logger disk failed and all data (including compass) were lost for this deployment.

Deployment IV: 4/17/97 - 6/10/97

 6 - BASS (ACM) velocity sets at (0.7, 1.1, 2.2, 3.3, 5.4 & 7mab)
6 - BASS travel-time sets at BASS ACM heights
2 - SeaBird temp, salinity sensors (0.7 & 7mab)
1 - ParoScientific pressure records (4.2mab)
1 - Compass, pitch & roll

The bottom-most BASS pod was disconnected to allow the implementation of a string of eight (8) YSI thermistors, which were placed near the sensing volume of each of the remaining BASS pods. A pin broke on the master ADV unit; therefore, there are no ADV data for this deployment.

Deployment V: 6/16/97 - 8/14/97

 (Same configuratioin as Deployment IV)

 The pre- and post-cruise zeroes differed for correcting BASS velocities. It appeared that they didn't relate to the data well, either. So, for the sake of simplicity, and the fact that the vertical velocities behaved well using this process, I assumed a circular tidal ellipse with a mean of zero. Also, the bottom-most SeaBird temperature sensor failed and the pressure and SeaBird conductivity cells also appeared flakey. One of the YSI thermistors mounted on the top-most BASS pod failed; but, it appeared that one of the thermistors from pod 6 had been moved up to pod 7 between Deployment IV and V.

ADVs were not included for this deployment.

DATA FILES

 Burst averages are availale via ftp as Matlab(4.2) data files.

They are grouped into two sets of time series:

  • sb1 contains data from Deployments I & II.

  • Note: sb1_adv contains data from Deployments I, II & III.
  • sb2_ contains data from Deployments IV & V.

  • Time (GMT) is stored as day of year (1997). The 'adv' data contain hourly bursts. All other files are three averages every two hours (eg, 12:15, 12:45, 13:15, 14:15, 14:45, 15:15, 16:15 ...). Also, remember that the ADVs are from the first nine (9) minutes of each hour, while the other data are 29 minute burst averages.

    bass - bass velocity files (m/s)
    tsd - SeaBird temperature and salinity with depth (from pressure at 4.2 mab)
    at - acoustic travel time (sum of both directions) in counts
    therms - YSI thermistor data in deg C (for sb2_ only)

    These data are not thoroughly cleaned up. Some wild data were replaced by NaNs for plotting purposes. Some wild data still remain in the data. These data are in a pre-release state and user should notify author below, so you will be notified of any changes or corrections.

    * This page created & maintained by J.J.Fredericks


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    Last Modified: September 3, 1998