SGP/SIRS/C1 - Reprocess: 4/24 - 5/9 Data at C1

Magnitude of data is correct, however, 2 wires were crossed producing negative values for 
SW Global Down, SW Global Up, SW Direct Normal, and SW Diffuse Down.
Problem has been fixed at site.

• Radiation, shortwave, downwelling total hemispheric irradiance, 1-min avg(down_short_hemisp)
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)
• 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)

SGP/SIRS/C1 - Diffuse Pyranometer Thermal Offsets

Broadband downwelling shortwave diffuse (sky) irradiance measurements available from SIRS
during the period of this Data Quality Report (DQR), require adjustment for thermal
offsets.  These thermal, or ?zero? offsets refer to the generally reduced output signals
from a shaded pyranometer due to the exchange of longwave (infrared) irradiance between
the single black thermopile detector, the protective glass domes surrounding the
detector, and the atmosphere. Originally considered an acceptable nighttime response of
thermopile-type pyranometers, the generally negative bias is now recognized to
significantly effect the accuracy of SIRS diffuse irradiance data during daylight
periods.

Studies of the Eppley Laboratory, Inc. Model PSP (Precision Spectral Pyranometer), used
for the SIRS   measurements of diffuse irradiance, suggest the thermal offset correction
can range from near 0 to as much as 30 Watts per square meter, depending on the
coincident net longwave, or infrared irradiance [1, 2].  Under very clear-sky conditions,
the diffuse irradiance from a shaded PSP can be less than the minimum physical limit
defined by radiative transfer model estimates based only on Rayleigh scattering effects.

A correction method has been developed for adjusting SIRS diffuse irradiance data [3]. 
The resulting Value Added Product (VAP) will be applied to SIRS data for the period of
this DQR.  The VAP will not be applied to SIROS data collected before the instrument
platform was converted to SIRS.

Additionally, the Model PSP radiometer has been replaced by a Model 8-48 which uses a
black and white thermopile detector known to reduce the thermal offset errors to less
than 2 Watts per square meter [3].  The radiometer replacement at this SIRS location was
completed on the ending date of this DQR.

References:
1. Gulbrandsen, A., 1978:  On the use of pyranometers in the study of spectral solar
radiation and atmospheric aerosols.  J. Appl. Meteorol., 17, 899-904.
2. Cess, R. D., X. Jing, T. Qian, and M. Sun, 1999:  Validation strategies applied to the
measurement of total, direct and diffuse shortwave radiation at the surface.  J. Geophys.
Res.
3. Dutton, E.G., J. Michalsky, T. Stoffel, B. Forgan, J. Hickey, D. Nelson, T. Alberta,
and I. Reda, 2001:  Measurement of Broadband Diffuse Solar Irradiance Using Current
Commercial Instrumentation With a Correction for Thermal Offset Errors. J. Atmos. Oceanic
Tech.   Vol 18, No. 3, 297-314.   (March 2001)

• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)
• down_short_diffuse_hemisp_std
• 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_diffuse

SGP/SIRS/C1 - Reprocess: Wire are switched

Upwelling longwave and downwelling longwave values are switched.  Instrument Engineering 
logs (OMIS) indicate the following:  "T/S indicated that the readings may be caused by the 
sensor wires being switched around.  Switched the wires labeled 5H with the wire labeled 
5L on the data logger.  The readings on the DIR went from minus readings to positive 
readings.  Will await further instruction from site scientist to perform any other PM".

• Radiation, longwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_long_hemisp)
• Irradiance, longwave, downwelling, hemispheric(down_long_hemisp)

SGP/BRS/C1 - low downwelling shortwave readings

Downwelling shortwave (DS) values frequently drop below -10 W/m^2 at night, and are 
consistently 20-40 W/m^2 less than the calculated downwelling shortwave during the day in 
clear-sky conditions. Corrective maintenance on 12/1/2004 corrected this offset.  It is not 
clear which CM action corrected the problem since the DS instrument cable was grounded to a 
new location and the DS ventilator fan was found in poor condition and was replaced.  
Either of these issues could have led to the problem observed in this instrument.

• down_short_hemisp_std
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Minima(down_short_hemisp_min)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Maxima(down_short_hemisp_max)
• Radiation, shortwave, downwelling total hemispheric irradiance, 1-min avg(down_short_hemisp)

• inst_global

• Raw data stream - documentation not supported

• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Maxima(down_short_hemisp_max)
• down_short_hemisp_std
• Radiation, shortwave, downwelling total hemispheric irradiance, 1-min avg(down_short_hemisp)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Minima(down_short_hemisp_min)

SGP/BRS/C1 - Missing data due to Ice storm and clock problems

Data are missing due to power failures caused by an ice storm
and resulting system/instrument clock problems.

• site
• base_time
• Measured Downwelling Diffuse Shortwave Irradiance (dif)(difswfluxdn_measured)
• solar_cos_z
• Measured Downwelling Direct Shortwave Irradiance (dir)(dirfluxdn_measured)
• sswfluxdn_cloudeffect
• nsamples_clearsky_detection
• time_offset
• time_offset_LST
• difratiodn_measured_stdev
• gswfluxdn_cloudeffect
• difcloudeffect_normalized
• sswfluxdn_clearskyfit
• Measured Downwelling Global Shortwave Irradiance (gsw)(gswfluxdn_measured)
• Measured Surface Albedo from Shortwave Irradiance Measurements (alb)(albedosw_measured)
• guvbdn_measured
• lon
• Clear-sky Fit Estimated Downwelling Direct Shortwave Irradiance (cdir)(dirfluxdn_clearskyfit)
• difratiodn_clearskyfit
• Clear-sky Fit Estimated Sfc. Albedo from Shortwave Irrad. Measurements (calb)(albedosw_clearskyfit)
• lat
• nsamples_cloudfraction
• sswfluxdn_measured
• difratiodn_measured
• Clear-sky Fit Estimated Downwelling Global Shortwave Irradiance (csw)(gswfluxdn_clearskyfit)
• guvbdn_clearskyfit
• sun_earth_distance
• difswfluxdn_cloudeffect
• nsamples_gswfluxdn_clearskyfit
• base_time_LST
• alt
• nsamples_sswfluxdn_measured
• Fractional Sky Cover(cloudfraction)
• Clear-sky Fit Estimated Downwelling Diffuse Field Shortwave Irradiance (cdif)(difswfluxdn_clearskyfit)

• up_long_hemisp_std
• Upwelling Shortwave Hemispheric Irradiance, Unventilated Pyranometer, Maxima(up_short_hemisp_max)
• vBatt
• Downwelling Longwave Hemispheric Irradiance, Shaded Ventilated Pyrgeometer(down_long_hemisp_shaded)
• Upwelling Shortwave Hemispheric Irradiance, Unventilated Pyranometer, Minima(up_short_hemisp_min)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• down_long_hemisp_shaded_std
• alt
• down_short_hemisp_std
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)
• up_short_hemisp_std
• down_short_diffuse_hemisp_std
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• time_offset
• lat
• short_direct_normal_std
• Downwelling Longwave Hemispheric Irrad., Shaded Ventilated Pyrgeometer, Minima(down_long_hemisp_shaded_min)
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Minima(up_long_hemisp_min)
• Downwelling Longwave Hemispheric Irrad., Shaded Ventilated Pyrgeometer, Maxima(down_long_hemisp_shaded_max)
• Radiation, shortwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_short_hemisp)
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Maxima(up_long_hemisp_max)
• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Maxima(down_short_diffuse_hemisp_max)
• base_time
• lon
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Minima(down_short_diffuse_hemisp_min)
• Radiation, shortwave, downwelling total hemispheric irradiance, 1-min avg(down_short_hemisp)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Minima(down_short_hemisp_min)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Maxima(down_short_hemisp_max)
• Radiation, longwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_long_hemisp)

• difswfluxdn_cloudeffect
• lat
• coef_clearsky_guvb_b
• coef_clearsky_guvb_a
• Clear-sky Fit Estimated Downwelling Direct Shortwave Irradiance (cdir)(dirfluxdn_clearskyfit)
• solar_cos_z
• sswfluxdn_measured
• guvbdn_measured
• coef_clearsky_albedo_a
• coef_clearsky_albedo_b
• Clear-sky Fit Estimated Sfc. Albedo from Shortwave Irrad. Measurements (calb)(albedosw_clearskyfit)
• sswfluxdn_cloudeffect
• coef_clearsky_ssw_a
• coef_clearsky_ssw_b
• coef_clearsky_difratio_b
• coef_clearsky_difratio_a
• sun_earth_distance
• coef_clearsky_gsw_b
• coef_clearsky_gsw_a
• coef_clearsky_dsw_c
• sun_earth_distance_dailyaverage
• coef_clearsky_dsw_a
• coef_clearsky_dsw_b
• lon
• base_time
• flag_clearsky_detection
• time_offset
• Measured Downwelling Direct Shortwave Irradiance (dir)(dirfluxdn_measured)
• difratiodn_clearskyfit
• guvbdn_clearskyfit
• coef_date
• Measured Downwelling Diffuse Shortwave Irradiance (dif)(difswfluxdn_measured)
• sswfluxdn_clearskyfit
• Clear-sky Fit Estimated Downwelling Diffuse Field Shortwave Irradiance (cdif)(difswfluxdn_clearskyfit)
• base_time_LST
• site
• difratiodn_measured
• Measured Downwelling Global Shortwave Irradiance (gsw)(gswfluxdn_measured)
• time_offset_LST
• alt
• Measured Surface Albedo from Shortwave Irradiance Measurements (alb)(albedosw_measured)
• Clear-sky Fit Estimated Downwelling Global Shortwave Irradiance (csw)(gswfluxdn_clearskyfit)
• gswfluxdn_cloudeffect

• inst_diffuse
• inst_down_long_shaded_dome_resist
• lon
• inst_up_long_dome_resist
• alt
• inst_up_short_hemisp
• lat
• base_time
• time_offset
• inst_global
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer1)(inst_down_long_hemisp_shaded_tp)
• inst_down_long_shaded_case_resist
• inst_up_long_hemisp_tp
• inst_up_long_case_resist
• inst_direct_normal

• Raw data stream - documentation not supported

• down_long_hemisp_shaded_std
• Upwelling Shortwave Hemispheric Irradiance, Unventilated Pyranometer, Maxima(up_short_hemisp_max)
• base_time
• lat
• inst_up_long_dome_temp
• alt
• up_long_hemisp_std
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Minima(down_short_hemisp_min)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• Upwelling Longwave Hemispheric Net Infrared(up_long_netir)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Maxima(down_short_hemisp_max)
• Radiation, shortwave, downwelling total hemispheric irradiance, 1-min avg(down_short_hemisp)
• Radiation, shortwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_short_hemisp)
• Upwelling Shortwave Hemispheric Irradiance, Unventilated Pyranometer, Minima(up_short_hemisp_min)
• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)
• lon
• Radiation, longwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_long_hemisp)
• inst_down_long_shaded_case_temp
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• down_short_diffuse_hemisp_std
• inst_up_long_case_temp
• Downwelling Longwave Hemispheric Net Infrared(down_long_netir)
• 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)
• Downwelling Longwave Hemispheric Irrad., Shaded Ventilated Pyrgeometer, Minima(down_long_hemisp_shaded_min)
• down_short_hemisp_std
• time_offset
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)
• inst_down_long_shaded_dome_temp
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Minima(up_long_hemisp_min)
• short_direct_normal_std
• Downwelling Longwave Hemispheric Irradiance, Shaded Ventilated Pyrgeometer(down_long_hemisp_shaded)
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Maxima(up_long_hemisp_max)
• up_short_hemisp_std
• Downwelling Longwave Hemispheric Irrad., Shaded Ventilated Pyrgeometer, Maxima(down_long_hemisp_shaded_max)
• vBatt

SGP/SIRS/C1 -

Data quality this month is OK. The noteable problems follow. Nighttime offsets in the 
Downwelling pyranometer (DS) average about -4 W/m^2 for the month. There are moderate 
inconsistencies between the Global (DS), Direct (NIP) and Diffuse (DD) components for 
the 1st, 2nd, 4th, 5th, 6th, 7th, 10th, 11th, 12th, 13th, 14th, 18th and 19th in the 
afternoon 
and the 1st, 2nd, 4th, 5th, 7th, 13th, 25th and 29th in the early morning. In every case 
the 
DD and NIP are too high and the DS is too low. This could be caused by the use of a 
constant pyranometer responsivity for all solar zenith angles, or the switchover from 

probable factor in the error. It should also be noted that the calibration factors for the 
PSP's have a 
tolerance of plus or minus 5% and the NIP has a tolerance of plus or minus 3%. The DS 
drops 
below daytime empirical limits on the 3rd from 7:50 PM to 9:40 PM 
GMT. This was most likely caused by the heavily overcast skies at the time. Visual and 
automated QC of the longwave components resulted in no noteable problems.

• alt
• Upwelling Shortwave Hemispheric Irradiance, Unventilated Pyranometer, Maxima(up_short_hemisp_max)
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Minima(down_short_diffuse_hemisp_min)
• Upwelling Shortwave Hemispheric Irradiance, Unventilated Pyranometer, Minima(up_short_hemisp_min)
• Radiation, shortwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_short_hemisp)
• Radiation, shortwave, downwelling total hemispheric irradiance, 1-min avg(down_short_hemisp)
• short_direct_normal_std
• base_time
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• lon
• down_long_hemisp_max
• lat
• vBatt
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Maxima(up_long_hemisp_max)
• down_short_hemisp_std
• down_short_diffuse_hemisp_std
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Maxima(down_short_diffuse_hemisp_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Minima(down_short_hemisp_min)
• time_offset
• down_long_hemisp_std
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyranometer, Maxima(down_short_hemisp_max)
• down_long_hemisp_min
• up_short_hemisp_std
• up_long_hemisp_std
• Radiation, longwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_long_hemisp)
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Minima(up_long_hemisp_min)
• Irradiance, longwave, downwelling, hemispheric(down_long_hemisp)
• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)

• down_long_case_resist
• lon
• Irradiance, longwave, downwelling, hemispheric(down_long_hemisp)
• base_time
• 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, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_short_hemisp)
• Observed direct-beam normal solar irradiance(nip)
• down_long_dome_resist
• short_diffuse
• up_long_case_resist
• alt
• time_offset
• lat
• up_long_dome_resist