| Start Date | Start Time | End Date | End Time | Data Quality Metric |
|---|---|---|---|---|
| 09/12/1994 | 1300 | 09/14/1994 | 1847 | Incorrect |
| Subject: | SGP/EBBR/E20 - Fan Stopped, T and RH Biases |
| DataStreams: | sgp30ebbrE20.b1, sgp5ebbrE20.b1, sgp15ebbrE20.b1 |
| Description: | Another fan stoppage situation occurred. This is the fourth one in the
last few months and may indicate a weakening of the fans that aspirate the
temperature, relative humidity housings. The 15 minute data reveals that
the stoppage occurred at approximately 1300 GMT on September 12. The left fan
was cleaned out by site operations personnel and began running again at
1847 GMT on September 14. The 15 minute data during this period shows that
during daytime, the left temperature was greater than the right temperature and
that the left relative humidity was lower than the right relative humidity
(a consequence of greater temperature), irregardless of the positions of the
housings. The bowen ratio, sensible heat flux and latent heat flux for this
period, as well as all left housing temperatures and relative humidities are
incorrect. The data values that are incorrect are:
5 minute: tair_top, tair_bot, thum_top, thum_bot, hum_top, hum_bot,
vp_top, vp_bot
15 minute: rr_thum_l, mv_hum_l, tair_l,
30 minute: tair_top, tair_bot, thum_top, thum_bot, hum_top, thum_bot,
vp_top, vp_bot, bowen, e, h
Because of the increased frequency of fan stoppage occurrences, I have
submitted a work request to site operations to use the portable vane
anemometer to check the flow of the housing fans on each EBBR and visually
check (and clean if needed) the fans for debris that would restrict the
flow. Included in this work request are instructions for checking the
performance of the temperature and relative humidity sensors by
manually putting the aspirator housings at the same height for a half hour
period (so that two 15 minute and one half hour comparison result).
The latter part of the work request is prompted by my close inspection of
the Meeker data for the last few weeks. It is clear that significant
biases have developed in the pairs of temperature and relative humidity
sensors; left thermocouple ~0.5 deg. C greater than right thermocouple,
left relative humidity ~5% lower than right relative humidity. Biases were
expected in operating the systems over long time periods, and these appear
to be the result of simple offsets, not changes in calibrations.
At this point, I just want to determine how large the offsets are.
Comparison of these offsets between EBBR units, in light of the different
lengths of time that EBBR units and individual sensors have been deployed,
may provide some interesting information on likely offset changes with time. |
| Suggestions: | |
| Measurements: | sgp30ebbrE20.b1: more
sgp15ebbrE20.b1: more sgp5ebbrE20.b1: more |