Description: | The daily average difference between the shaded and unshaded PIRs
reversed on 19980428. Previous to then, the unshaded PIR was typically
about 2 Wm-2 less than the shaded PIR. Since the 28th, the unshaded
PIR has been averaging about 4-5 Wm-2 greater than the shaded PIR.
This latter difference worsened for the period 5/25 to 5/31, when the
daily average difference increased to between 8-10 Wm-2. The
disagreement is typically greater at night, reaching differences of
greater than 12 Wm-2 during the period 5/25-5/31. The cause for the
switch in sign of the difference can most likely be attributed to
instrument replacement, however the (in general) larger absolute
disagreement after Apr 28th indicates a possible calibration problem.
The cause of the large discrepancies from 5/25 to 5/31 is unknown.
I noticed that the daylight differences increased slightly, with an
attendant slight decrease in the night differences. This daylight
difference is on the order of an additional 1 Wm-2.
Note: the unshaded PIR is incorrectly named "shaded2" during this
time period. This is covered in a separate DQR. |