SGP/SIRS/E10 - 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Additionally, the Model PSP radiometer has been replaced by a Model 8-48 which uses a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)

• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Minima(down_short_diffuse_hemisp_min)
• down_short_diffuse_hemisp_std
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Maxima(down_short_diffuse_hemisp_max)

• short_diffuse

SGP/SIRS/E11 - 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)

• short_diffuse

• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Maxima(down_short_diffuse_hemisp_max)
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Minima(down_short_diffuse_hemisp_min)
• down_short_diffuse_hemisp_std

SGP/SIRS/E12 - 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)

• short_diffuse

• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Minima(down_short_diffuse_hemisp_min)
• down_short_diffuse_hemisp_std
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Maxima(down_short_diffuse_hemisp_max)
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)

SGP/SIRS/E15 - 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)

• down_short_diffuse_hemisp_std
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Minima(down_short_diffuse_hemisp_min)
• Radiation, shortwave, downwelling diffuse hemispheric irradiance, 1-min avg(down_short_diffuse_hemisp)
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Maxima(down_short_diffuse_hemisp_max)

• short_diffuse

SGP/SIRS/E16 - 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)

• short_diffuse

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

SGP/SIRS/E10

Direct (NIP) exceeds 5 W/m^2, triggering yellow flags. This test was designed more 
for daytime conditions.

• Irradiance, longwave, downwelling, hemispheric(down_long_hemisp)
• down_long_hemisp_std
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Maxima(up_long_hemisp_max)
• down_long_hemisp_min
• Radiation, longwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_long_hemisp)
• up_long_hemisp_std
• down_long_hemisp_max
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Minima(up_long_hemisp_min)

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

SGP/SIRS/E10  -

Data quality this site-month is OK. Nighttime offsets for the Global (DS) and Diffuse (DD) 

pyranometers are -5 W/m^2 a piece. DS dips below its daytime empirical limits on the 
3rd, 8th, 16th, and 27th for various lengths of time. DD goes below daytime empirical 
limits on the 8th from 15:15 to 17:30 GMT and goes below its nighttime empirical limit 
immidiately after sunset on the 19th. There are inconsistencies between the Global (DS), 

11th, 12th, 13th, 25th, 30th, 31st in the afternoon. These inconsistencies range in 
severity 
from mild to substansial even though they all trigger yellow flags only (or stay green). 
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 daylight to twilight testing regimes. The daytime negative offset in the 
DS 
PSP is also a probable factor in the error. It should also be noted that the calibration 

plus or minus 3%. There are also two component (Gompertz boundaries) problems this 
month: NIP and DD are flagged as too high on the 3rd and 8th for short periods of time. 
There is a small but persistent problem with the Upwelling Shortwave (US) data during this 
time
 period. At dusk the US is below its twilight empirical limits almost every day at dusk.

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

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

SGP/SIRS/E11

Direct (NIP) exceeds 5 W/m^2, triggering yellow flags. This test was designed more 
for daytime conditions.

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

• down_long_hemisp_max
• Irradiance, longwave, downwelling, hemispheric(down_long_hemisp)
• Radiation, longwave, at 10-m height, upwelling hemispheric irrad., 1-min avg(up_long_hemisp)
• down_long_hemisp_std
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Minima(up_long_hemisp_min)
• Upwelling Longwave Hemispheric Irradiance, Unventilated Pyrgeometer, Maxima(up_long_hemisp_max)
• down_long_hemisp_min
• up_long_hemisp_std

SGP/SIRS/E11  -

Data quality this site-month is good. Nighttime offsets for the Global (DS) and Diffuse 
(DD) 
pyranometers are -5 W/m^2 a piece. There are also two component (Gompertz 
boundaries) problems this month: Direct (NIP) and DD are flagged as too high on the 3rd 
for a short period of time. DS dips below its daytime empirical limits on the 3rd and 23rd 

and Upwelling Longwave dips below the empirical limits from 12:20 to 14:50 GMT. The 
winter Longwave empirical limit of 250 W/m^2 is currently under further review. (A reading 

of 250 W/m^2 suggests a possible temperature between 5 and 20 degrees Fahrenheit.) 
Upwelling Shortwave 
(US) is below its nighttime empirical limit for a little while after the sun goes down on 
the 12th.

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

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

SGP/SIRS/E12

Data quality this site-month is good. Nighttime offsets in the Downwelling pyranometer 
(DS) average about -4 W/m^2 for the month. The Downwelling Diffuse pyranometer (DD) 
averages about -5 W/m^2 for its nighttime offset. DD and DS go below daytime empirical 
limits late in the day on the 3rd and 8th late in the day and on the 16th early in the 
day. 
Diffuse also exceeds daytime empirical limits earlier in the day on the 3rd. There are 
moderate 
inconsistencies between the Global (DS), Direct (NIP) and Diffuse (DD) components for 
the 4th in the afternoon. 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 daylight to twilight testing regimes. The daytime negative offset in the DS PSP is 
also a 
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%.

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

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

SIRS NIPs affected by condensation at E8, E11, E13, & E15

Comparison of data from the unshaded PSP to that derived from the 'direct
+ diffuse' (NIP + shaded PSP) indicated low values of the 'direct+diffuse' combination 
starting at sunrise and lasting for about an hour at E8, E11, E13 and E15.
Futher examination revealed that the NIPs were reading low and were likely
affected by condensation during this brief period. Weather conditions were
foggy over the area early that morning, and fog quickly dissipated after 
sunrise.

• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• short_direct_normal_std
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)

• short_direct_normal_std
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)

• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)
• short_direct_normal_std
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)

• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• short_direct_normal_std
• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)

SGP/SIRS - SIRS E10  April 1999  (SERI-QC Results)

Data quality for this site is excellent this month. Daytime data are 100 %
present. Of the present daytime data, 98% are at or below the 5% quality 
assurance threshold. Severe flags early in the morning on the 4th through
the 21st, and on the 30th indicate that the DS, DD and NIP are above 
twilight empirical limits. Low-level flags later in the morning and around
mid-day during the second week of the month indicate that the DS is too low
by the three-component test, or that the DD or NIP is too high. Low-level
flags late in the afternoon on clear or partly cloudy days indicate the 
opposite. Heavily overcast skies pushed the DS and DD below daytime or 
twilight empirical limits on a number of occasions. On the afternoon of the
22nd   the NIP, along with the DD and DS signals, fell below daytime limits 
for a few minutes. Moderate flags later the same day indicate that the DS 
is too high by the three-component test.  No problems are notes in the UIR,
DIR or US signals.

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

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

SGP/SIRS - SIRS E11 April 1999 (SERI-QC Results)

Data quality for this site is very good this month. All daytime data are present, and 96% 
of the present daytime data earn passing or low-level flags. Low-level flags are seen in 
the early morning hours under clear to fair sky conditions, indicating that the DS 
(global horizontal) is too low, or that the NIP (direct normal) or DD (diffuse horizontal) is 
too high. Overcast skies cause the DD and DS to fall below twilight or daytime empirical 
limits on a number of occasions. The suntracker failed for an hour or so on the morning of 
the 6th. During Preventive Maintenance later in the morning the alignment was adjusted. 
No problems noted in the UIR, DIR or US signals.

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

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

SGP/SIRS - SIRS E12  April 1999  (SERI-QC Results)

Data quality at this site is very good this month. Not quite 100% of the data are present, 
and 91% of the present daytime data earned passing or low-level flags. Another 8.1% of 
the daytime data earn strange-but-true flags. Low-level flags seen from late morning to 
early afternoon on clear and partly cloudy days throughout the month indicate that the DS 
is too high by the three-component test. Alternatively, the DD or NIP may be too low. 
Heavily overcast skies drove the DS and DD below daytime or twilight empirical limits on a 
few occasions, and the NIP was forced below daytime empirical limits on the afternoon of 
the 22nd. On the 20th the phone line to the site was tested and found to be of poor quality 
for data transmittal. This is likely the cause of the spotty data retrieval from this 
site over the past several months. On the morning of the 21st the 10m tower was removed for 
upgrade so the US and UIR signals are missing recorded as 99999 by the data logger. No 
other problems are noted.

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

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