SGP/QCRAD/E2 - Possible calibration error

Either the downwelling shortwave or the shortwave diffuse radiometer appears to have a 
large calibration error. This also impacts the best estimate data. It is not clear when this 
problem started or was fixed, so the dates in this DQR may not fully describe the problem.

Described in instrument DQR D970310.1.

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.

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• Quality check results on field: Best Estimate Global Downwelling Shortwave
  Hemispheric Irradiance(BestEstimate_down_short_hemisp)
• Down-welling unshaded pyranometer voltage(down_short_hemisp)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)

• Quality check results on field: Best Estimate Global Downwelling Shortwave
  Hemispheric Irradiance(BestEstimate_down_short_hemisp)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)

• Down-welling unshaded pyranometer voltage(down_short_hemisp)
• Quality check results on field: Best Estimate Global Downwelling Shortwave
  Hemispheric Irradiance(BestEstimate_down_short_hemisp)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)

• Quality check results on field: Best Estimate Global Downwelling Shortwave
  Hemispheric Irradiance(BestEstimate_down_short_hemisp)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)