SGP/SIRS/C1 - Discrepancy between measured and derived downwelling shortwave hemispheric

Measured values of downwelling hemispheric shortwave radiation were up to 40 W/m^2 higher 
than derived values during the afternoon hours.

Analysis reveals that this is likely an artifact of the cosine response of the particular 
installed PSP coupled with typical uncertainties of this set of installed radiometers.   
That is, this particular instrument cluster seems to be producing cumulative errors on 
the high side of accepted values.

The PSP contains the most uncertainty in measurement at this station. Users should use a 
derived value for the downwelling shortwave hemispheric irradiance (DS). Where DS = 
diffuse component + direct normal * cos(SZA) component described in the SIRS handbook Sec 7.2 
available at: http://www.arm.gov/publications/tech_reports/handbooks/sirs_handbook.pdf

• inst_diffuse
• inst_global
• inst_direct_normal

• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Minima(down_short_diffuse_hemisp_min)
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Maxima(down_short_diffuse_hemisp_max)
• short_direct_normal_std
• Radiation, shortwave, downwelling total hemispheric irradiance, 1-min avg(down_short_hemisp)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Minima(down_short_hemisp_min)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Maxima(down_short_hemisp_max)
• down_short_hemisp_std
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• down_short_diffuse_hemisp_std
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)
• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)

SGP/SIRS/C1/E13 - Incorrect calibration coefficients

After the DIR changeout on 8/27, the DLH measurements at the central facility vary 
significantly between pyrgeometers by as much as 65 Wm^(-2).  It was discovered that the two 
downwelling pyrgeometers destined for C1 and E13 may have been swapped during installation.  
The instrument mentor is unsure of applied calibration coefficients during this DQR's 
time period.  Backing out new downwelling longwave irradiances would be difficult in this 
case. Fortunately, the problem period is less than a fortnight.

• inst_down_long_shaded_dome_resist
• inst_down_long_shaded_case_resist
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer1)(inst_down_long_hemisp_shaded_tp)

• Raw data stream - documentation not supported

• inst_down_long_shaded_case_resist
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer1)(inst_down_long_hemisp_shaded_tp)
• inst_down_long_shaded_dome_resist

• Raw data stream - documentation not supported

• inst_down_long_shaded_case_temp
• Downwelling Longwave Hemispheric Net Infrared(down_long_netir)
• Downwelling Longwave Hemispheric Irradiance, Shaded Ventilated Pyrgeometer(down_long_hemisp_shaded)
• Downwelling Longwave Hemispheric Irrad., Shaded Ventilated Pyrgeometer, Minima(down_long_hemisp_shaded_min)
• down_long_hemisp_shaded_std
• Downwelling Longwave Hemispheric Irrad., Shaded Ventilated Pyrgeometer, Maxima(down_long_hemisp_shaded_max)
• inst_down_long_shaded_dome_temp

• Downwelling Longwave Hemispheric Irrad., Shaded Ventilated Pyrgeometer, Maxima(down_long_hemisp_shaded_max)
• Downwelling Longwave Hemispheric Irrad., Shaded Ventilated Pyrgeometer, Minima(down_long_hemisp_shaded_min)
• down_long_hemisp_shaded_std
• Downwelling Longwave Hemispheric Net Infrared(down_long_netir)
• Downwelling Longwave Hemispheric Irradiance, Shaded Ventilated Pyrgeometer(down_long_hemisp_shaded)
• inst_down_long_shaded_case_temp
• inst_down_long_shaded_dome_temp

SGP/SIRS/C1 - Reprocess: UIR/DIR Incorrect calibration coefficients

It appears the datalogger program at SIRS/C1 was automatically updated, unbeknownst to 
anyone, on 9/27/20041423GMT with an older program with incorrect UIR and DIR calibration 
coefficients. The correct and incorrect cal coeffs for the UIR and DIR pyrgeometers during 
this DQR period were:
  incorrectUIR   correctUIR
K0  -12.84       -13.00
K1  .2250        0.2573
K2  1.024        1.024
K3  -1.9280      -1.8050

 incorrectDIR   correctDIR
K0  -13.15       -26.89
K1  0.2374       0.2967
K2  1.0260       1.0560
K3  -2.478       -3.3080

• Raw data stream - documentation not supported

• Downwelling Longwave Hemispheric Irrad., Shaded Ventilated Pyrgeometer, Maxima(down_long_hemisp_shaded_max)
• Upwelling Longwave Hemispheric Net Infrared(up_long_netir)
• Downwelling Longwave Hemispheric Irrad., Shaded Ventilated Pyrgeometer, Minima(down_long_hemisp_shaded_min)
• down_long_hemisp_shaded_std
• Downwelling Longwave Hemispheric Net Infrared(down_long_netir)
• Downwelling Longwave Hemispheric Irradiance, Shaded Ventilated Pyrgeometer(down_long_hemisp_shaded)
• up_long_hemisp_std
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Minima(up_long_hemisp_min)
• inst_up_long_dome_temp
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Maxima(up_long_hemisp_max)
• inst_up_long_case_temp
• inst_down_long_shaded_case_temp
• Radiation, longwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_long_hemisp)
• inst_down_long_shaded_dome_temp

SGP/SIRS/C1 - Monthly Summary

dominant problem here is the daytime 3 component problem. Direct and Diffuse are
always too high and Global is too low. The problem occurs around the time that the
testing regime switches from twilight to daytime testing regimes or from daytime to
twilight. The flags occur in significant numbers on the 1st - 5th, 8th - 20th, 24th - 
28th,
30th, and 31st. The failures vary in magnitude and duration. The worst flags for a 
particular
day is typically high level yellow, with respect to this problem. Global goes below
daytime empirical limits on both the 5th and 6th for substantial periods of time. Diffuse
also goes below daytime empirical limits on the 6th in the evening. Upwelling Longwave is
below empirical limits on the 24th. This may not be a problem, as many sites exhibited
the same problem on the same night. Exceptionally cold temperatures may be the cause.
Direct also exceeds its daytime empirical limit on the 1st, 4th, 10th, 13th, 14th, and 
20th. This occurs
at the changeover from medium to high air mass and does not last for longer than 30 
minutes.

• Radiation, shortwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_short_hemisp)
• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)
• Downwelling Longwave Hemispheric Irradiance, Shaded Ventilated Pyrgeometer(down_long_hemisp_shaded)
• Radiation, shortwave, downwelling total hemispheric irradiance, 1-min avg(down_short_hemisp)
• Radiation, longwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_long_hemisp)
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)

SGP/SIRS/C1 - Reprocessed: Longwave Calibration error

Modified pyrgeometer calibration procedures were implemented beginning in December 2003. 
These modified procedures introduced a calibration bias in the longwave data. The previous 
procedures were re-implemented at all sites between December 2005 and February 2006 to 
restore proper calibrations. 

The data collected while the incorrect procedures were in place have been reprocessed to 
remove the calibration bias.  The reprocessed 60 second averaged data are based on 3 
instantaneous 20 second data records rather than on 60 1 second instantaneous data records. 
Still, these data are considered far superior to the originally processed data. The 
reprocessed data were archived in October 2006.

• Upwelling Longwave Hemispheric Net Infrared(up_long_netir)
• Downwelling Longwave Hemispheric Net Infrared(down_long_netir)
• Downwelling Longwave Hemispheric Irradiance, Shaded Ventilated Pyrgeometer(down_long_hemisp_shaded)
• Radiation, longwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_long_hemisp)