DQRID : D120417.10
Start DateStart TimeEnd DateEnd Time Data Quality Metric
02/20/1997000003/06/19971500Incorrect
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Subject:
SGP/QCRAD/E2 - Tracker inoperative
DataStreams:sgpqcrad1longE2.c2, sgpqcrad1longE2.c1, sgpqcrad1longE2.s1, sgpqcrad1longE2.s2
Description:
Solar tracker inoperative. Described in instrument DQR D970310.1.

From about 97/02/20 to 97/03/06 (1500 GMT) the solar tracker was inoperative
at site E2.  We cannot pin down the exact starting time of this failure
because of cloudy conditions around 97/02/20.  The failure becomes obvious
during clear skis at which time the NIP reads zero (i.e., it isn't pointed
at the sun) and the downward diffuse radiation is too large (because the
diffuse pyranometer is not being shaded).  97/03/03 was a particularly 
clear day and the diffuse pyranometer reads almost the same as the total
downward pyranometer.  The fact that they don't read exactly the same - the
discrepency is about 75 W/m^2 at solar noon - is indicative of a large sensor
calibration problem.  This large calibration error is NOT typical of ARM 
data, rather it is peculiar to this site.
Suggestions: 
Don't use SW direct or diffuse data during these time periods. If 

"source_BestEstimate_down_short_hemisp" is 0, don't use Best Estimate GSW data. Note that fewer quality 
checks can be applied accurately to the BestEstimate data.
Measurements:sgpqcrad1longE2.s2:
  • short_direct_normal
  • down_short_diffuse_hemisp
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sgpqcrad1longE2.c2:
  • short_direct_normal
  • down_short_diffuse_hemisp
more
sgpqcrad1longE2.c1:
  • short_direct_normal
  • down_short_diffuse_hemisp
more
sgpqcrad1longE2.s1:
  • short_direct_normal
  • down_short_diffuse_hemisp
more

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