DQRID : D040806.4
Start DateStart TimeEnd DateEnd Time Data Quality Metric
10/13/2003002511/05/20032359Does not affect quality
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Subject:
SGP/AERI/B5 - Increased radiative uncertainty during hot summer afternoons
DataStreams:sgpaerich1B5.b1, sgpaerich2B5.b1
Description:
The ambient temperature of the AERI enclosures at the boundary facilities
often exceeded 308 K during hot summer afternoons.  This threshold marked
the maximum end of the "acceptable" range of temperatures that the 
ambient blackbody should maintain.  The issue is that if the hot 
blackbody and ambient blackbody temperatures are too close together, then 
the radiative calibration becomes more uncertain.  It should be noted 
that the hot blackbody's temperature is maintained at roughly 333 K.  

Using the calibration equation, an uncertainty analysis was performed
to see how much "additional" uncertainty resulted in the AERI
observations when the ambient temperature was between 308-315 K (315 K
was the maximum temperature that the ambient blackbody reached during
the summer).  The analysis compared the radiative uncertainties from the
Hillsboro (B1) AERI (chosen at random) with the AERI-01 at the SGP/CF
over a 5-year period.  Plot1 (below) shows the time-series of ambient
blackbody temperatures for the two instruments, along with histograms to
show the distribution of the temperatures.  The boundary facility
instrument did suffer from higher temperatures in the summer
time periods.  Plot2 (bleow) shows the relative radiative uncertainty
for each instrument.  The CF instrument has a maximum radiative
uncertainty of around 0.18% during the summer, while the BF instrument's
maximum radiative uncertainty is about 0.25%.  This plot demonstrates
that the radiative uncertainty is significantly larger for the BF
instrument in the summer relative to the CF instrument.  However, the
absolute radiative accuracy for the AERI is specified to be better than
1% of the ambient radiance, and both the CF and the BF AERIs are well
within this uncertainty.  

In short, there is significantly higher radiative uncertainty in the
BF AERIs during the hot summer afternoons, but the uncertainty is well
within the specified accuracy of the instrument.

plot1:  aeri_abb_temp.lamont_hillsboro.png 

plot2:  aeri_relative_error.lamont_hillsboro.png 
Suggestions: 
Be an informed data user and consider how this additional uncertainty might affect 

your analysis.
Measurements:sgpaerich1B5.b1:
  • mean_rad
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sgpaerich2B5.b1:
  • mean_rad
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