Having posted
a similar message on the Angel's Reef (Speyside) buoy's blog, I am continuing my data analysis by turning to the Buccoo Reef buoy. These messages were prompted by an absence of any updates from the field -- basically I am trying to see what we can conclude about local events based only on examination of the data.
As a reminder, this station's recent history includes
its annual equipment swapout
(December 9th - 10th, 2015), at which time the EXO Sonde was reinstalled
after been absent for warranty repairs since July 17st, 2015. These
repairs included an upgrade to a titanium bulkhead and the replacement
of the CT module (conductivity/temperature sensor, which reports
salinity as well) with an improved CT2 module. It was hoped that the
reengineered CT2 module would eliminate the many problems with failures
of the temperature and salinity parameters experienced over this
station's lifetime since late 2013. After the 12/10/2015 swapout was
completed, no further updates were received apart from
an announcement on February 5th, 2016, that Jahson Alemu would no longer be our primary local contact for the Tobago buoys.
As of May 16th, 2016, the following observations can be made about this buoy's data stream:
- The EXO Sonde was indeed reconnected during the annual swapout and
started producing data on December 10th, 2015, after an
absence of nearly five months.
- The EXO Sonde went offline from March 16th to 19th, 2016. My guess
would be that the instrument was removed for three days during some kind
of maintenance operation, which seems likely considering that the EXO at the Angel's Reef buoy went offline for five days at the same time (March 18th - 23rd).
- The Buccoo Reef EXO additionally went offline twice in May, once for two hours on May 1st, 2016, and then again for one day from May 4th - 5th, 2016.
- Since last December, apart from the aforementioned interruptions in March and May, the
EXO seems have produced consistent and reliable sea temperature data.
- Compared to the performance of the EXO at Angel's Reef, this Buccoo EXO's salinity data are more believable. In the absence of a second conductivity/salinity sensor on-site giving redundant data reports, nothing can be said for certain, but it is at least possible that the CT2 sensor at Buccoo Reef is producing reliable salinity data.
- As for the other EXO parameters: Turbidities might be okay; Chlorophyll, Blue-Green Algae and FDOM fluctuate above and below zero and those sensors may be bad (or badly calibrated); pH data are either garbage or missing; and dissolved oxygen values may be reasonable.
- The analog AirT/RH sensor remains offline, as it has been since early 2014. Based on my experience with a similar failure and repair at
the Calabash Caye buoy I believe that this is likely to be a problem with
buoy wiring and not a failure of the RM Young sensor itself.
- We do, however, have air temperature and humidity reports from
the integrated WXT unit. Although these reports cannot be validated by
redundant readings from the analog AirT/RH sensor, they appear to be
believable.
- Wind speeds and directions, as well as barometric pressures,
continue to be reported redundantly by multiple sensors, and all appear
to be consistent and correct.
- Of the two diagnostic RH (humidity) sensors with the buoy's two sealed junction boxes (JBs), the "Met" JB humidity levels are perfectly dry, as they have been throughout this buoy's lifetime. However the "Main" JB humidity levels are all consistently above 80% and are a cause for concern. The Main JB humidity levels were only moderate before the 12/10/2015 annual maintenance operation, and jumped much higher afterwards, suggesting that the Main JB may not have been sealed/dried properly, may require fresh desiccant, or may have developed some kind of leak/crack. This JB's o-ring, desiccant and interior should be examined at the earliest possible opportunity.
We do not have any reports about how often the EXO Sonde's
modules have been recalibrated on-site since December of 2015. According
to the manufacturer many of these modules should be recalibrated on a
monthly basis.
I will post any further updates that are
received at AOML. The next annual maintenance operation should be
carried out this coming December, or earlier.
Mike J+
