AirT/RH performance at Little Cayman, 2013-present

This post is part of a planned series of posts to share the results of my recent evaluation of data produced by all of the CREWS/CCCCC buoys over their lifetimes, from 2013 to the present.  This post will discuss the performance of the analog instruments which measure air temperature (AirT) and relative humidity (RH).  These analog reading serve as a basis of comparison for AirT/RH measurements reported by the Vaisala Weather Transmitter (WXT) which also reports wind, barometric pressure and precipitation data.

At Little Cayman the analog AirT/RH sensor's first deployment lasted 226 days before both the AirT and RH data simultaneously went bad on June 6, 2014.  [All instruments on a CREWS/CCCCC buoy are intended to produce usable data for an entire year.]  The buoy was brought to land for an annual maintenance operation on October 14-29, 2014 and suffered a power loss on December 29, 2014 that was repaired on land before redeployment on March 12, 2015.  The AirT/RH appears to have been successfully repaired/replaced during the October 2014 operation and has produced reasonable data since then.  This amounts to 150 days of reasonable AirT/RH data and counting, or 223 days and counting if you assume that the sensor would have operated properly during the buoy's extended power outage.

Note that at the time of the buoy's March 2015 redeployment it was discovered that the WXT communications had failed, so as of this writing there are no redundant AirT or RH readings available to compare against the analog AirT/RH readings.

The following are graphs of AirT (top, in °C) and RH (bottom, in %) from the Little Cayman buoy's lifetime, from 2013 to the present.  Values reported from the analog sensor under discussion are in blue and values from the WXT are in red.  Data are shown through June 9, 2015.

Please click on this image to see it in larger form.

Based on this data record the CCMI2 (Little Cayman) buoy's AirT/RH sensor performed reasonably well for 376 days out of the buoy's 506 operational days, or about 74% of the time.  Its longest stretch of proper operation was 226 days, or about 7.4 months.

Similar analysis performed on this buoy's sister stations at Buccoo Reef, Tobago (BUTO1) and Speyside / Angel's Reef (ARTO1) found that the BUTO1 instrument performed reasonably well for 90 days out of the buoy's 469 operational days, or about 19% of the time, and the ARTO1 instrument performed reasonably well for 181 days out of the buoy's 557 operational days, or about 32% of the time.  The BUTO1 sensor's longest stretch of proper operation was 90 days, or about 3.0 months, and the ARTO1 sensor's longest stretch of proper operation was 181 days, or about 6.0 months.

The complete analyses for the other AirT/RH sensors, including graphs, may be found at this link for BUTO1 and at this link for ARTO1.

(signed)
Mike Jankulak