NSA/SKYRAD/C1 - itermittant IRT bias

A problem with the SKYRAD IRT that itermittantly produced a gradual increase in the sky 
temperature measurement then a sudden correction, as compared to AERI, appears to have been 
caused by a combination of a failing IR detector, a poor signal cable, a contaminated 
(with condensation or frost) mirror or lens, and low ambient temperatures. The positive 
bias was apparently not consistant in either frequency or duration but on days when the 
unusual behavior is observed, it usually occurred from about 00:00 to 06:00 local time. 

The instrument was repaired and recalibrated and the signal cable replaced.

• Sky/Cloud Infra-Red Temperature Minima(sky_ir_temp_min)
• Sky/Cloud Infra-Red Temperature Maxima(sky_ir_temp_max)
• Sky/Cloud Infra-Red Temperature Standard Deviation(sky_ir_temp_std)
• Sky/Cloud Infra-Red Temperature(sky_ir_temp)

NSA/SKYRAD/C1 - IRT failure

The IRT failed and was replaced with a spare.

• Sky/Cloud Infra-Red Temperature Minima(sky_ir_temp_min)
• Sky/Cloud Infra-Red Temperature Maxima(sky_ir_temp_max)
• Sky/Cloud Infra-Red Temperature Standard Deviation(sky_ir_temp_std)
• Sky/Cloud Infra-Red Temperature(sky_ir_temp)

NSA/SKYRAD/C1 - Power outage affecting some SKYRAD instruments

During the power outage the downwelling global measurement from the PSP instrument and 
downwelling diffuse 8-48 instrument shows a slight increase from -5 to +0 W/m2.  This is due 
to removal of thermal offsets induced by the AC heater during the power outage.  This 
heater is installed within the PSP ventilator - it is necessary for the NSA/C1 climate.
The downwelling longwave PIR instrument is unaffected due to case and dome temperature 
corrections.
The IRT is AC powered and was not operational during this time period.

• Raw data stream - documentation not supported(Raw data stream - documentation not supported)

• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer,
  Minima(down_short_diffuse_hemisp_min)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer(down_short_hemisp)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Maxima(down_short_hemisp_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Standard
  Deviation(down_short_hemisp_std)
• Sky/Cloud Infra-Red Temperature(sky_ir_temp)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer,
  Maxima(down_short_diffuse_hemisp_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Minima(down_short_hemisp_min)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer,
  Standard Deviation(down_short_diffuse_hemisp_std)

• Instantaneous Downwelling Hemispheric Shortwave, Unshaded Pyranometer Thermopile
  Voltage(inst_global)
• Instantaneous Sky/Cloud Infrared(inst_sky_ir_signal)
• Instantaneous Uncorrected Downwelling Shortwave Diffuse, Shaded Pyranometer
  Thermopile Voltage(inst_diffuse)

NSA/SKYRAD/C1 - Instrument noise

Skyrad data appears affected by noise creating bias in analog voltage readings on 
02/15/2006 from 1300-1800GMT and again on 02/16/2006 from 1300-1500GMT.  The second night the 
noise is attenuated significantly.  By 02/17 no bias/noise is detectable. The thermistor 
measurements in PIR1 and PIR2 were unaffected during these excursions and showed no 
deviation from normal during the problem period.  In addition, the onboard logger temperature and 
battery voltage read normal throughout.  The problem has not reappeared as of 4/25/2006.

• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer,
  Minima(down_short_diffuse_hemisp_min)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Maxima(down_short_hemisp_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer(down_short_hemisp)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer1, Minima(down_long_hemisp_shaded1_min)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer2, Minima(down_long_hemisp_shaded2_min)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer1(down_long_hemisp_shaded1)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Standard
  Deviation(down_short_hemisp_std)
• Sky/Cloud Infra-Red Temperature(sky_ir_temp)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer2(down_long_hemisp_shaded2)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer,
  Maxima(down_short_diffuse_hemisp_max)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• Sky/Cloud Infra-Red Temperature Minima(sky_ir_temp_min)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer1, Maxima(down_long_hemisp_shaded1_max)
• Sky/Cloud Infra-Red Temperature Maxima(sky_ir_temp_max)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Standard Deviation(short_direct_normal_std)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer2, Maxima(down_long_hemisp_shaded2_max)
• Sky/Cloud Infra-Red Temperature Standard Deviation(sky_ir_temp_std)
• Shortwave Direct Normal Irradiance, Pyrheliometer(short_direct_normal)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Minima(down_short_hemisp_min)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer1, Standard
  Deviation(down_long_hemisp_shaded1_std)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer(down_short_diffuse_hemisp)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer2, Standard
  Deviation(down_long_hemisp_shaded2_std)
• Downwelling Shortwave Diffuse Hemispheric Irradiance, Ventilated Pyranometer,
  Standard Deviation(down_short_diffuse_hemisp_std)

• Instantaneous Downwelling Pyrgeometer Thermopile, Shaded Pyrgeometer2(inst_down_long_hemisp_shaded2_tp)
• Instantaneous Downwelling Pyrgeometer Dome Thermistor Resistance, Shaded
  Pyrgeometer1(inst_down_long_shaded1_dome_resist)
• Instantaneous Downwelling Pyrgeometer Dome Thermistor Resistance, Shaded
  Pyrgeometer2(inst_down_long_shaded2_dome_resist)
• Instantaneous Downwelling Pyrgeometer Case Thermistor Resistance, Shaded
  Pyrgeometer1(inst_down_long_shaded1_case_resist)
• Instantaneous Downwelling Pyrgeometer Case Thermistor Resistance, Shaded
  Pyrgeometer2(inst_down_long_shaded2_case_resist)
• Instantaneous Sky/Cloud Infrared(inst_sky_ir_signal)
• Instantaneous Downwelling Pyrgeometer Thermopile, Shaded Pyrgeometer1(inst_down_long_hemisp_shaded1_tp)
• Instantaneous Downwelling Hemispheric Shortwave, Unshaded Pyranometer Thermopile
  Voltage(inst_global)
• Instantaneous Direct Normal Shortwave Irradiance, Pyrheliometer Thermopile
  Voltage(inst_direct_normal)
• Instantaneous Uncorrected Downwelling Shortwave Diffuse, Shaded Pyranometer
  Thermopile Voltage(inst_diffuse)

NSA/SKYRAD/C2 - Summer solstice shading of radiometers

On and around the summer solstice, the NIP (Direct Normal shortwave measurement) and PSP 
(global hemispheic shortwave measurement) radiometers are shaded by other instruments or 
support structures. Shading azimuths have been determined for this site.  The radiometer 
mentor suggests not using the data from the NIP and PSP radiometers when the sun is within 
the following azimuth bounds (typically from May 8th to August 5th of each year):
Instr   Obstruction   AzStart   AzEnd
NIP     rad table     356       17
PSP     mfrsr         341       353

Note: There are a number of objects near the NW,N and NE horizon that may affect sunrise 
data near the summer soltice.

• PSP1 unshaded standard deviation(psp1_sd)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Minima(down_short_hemisp_min)
• PSP shaded standard deviation(psps_sd)
• PSP shaded mean(psps_mean)
• NIP maximum(nip_max)
• NIP mean(nip_mean)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer(down_short_hemisp)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Standard Deviation(short_direct_normal_std)
• PSP1 unshaded maximum(psp1_max)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Standard
  Deviation(down_short_hemisp_std)
• NIP minimum(nip_min)
• NIP standard deviation(nip_sd)
• PSP1 unshaded minimum(psp1_min)
• PSP shaded minimum(psps_min)
• PSP1 unshaded mean(psp1_mean)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Maxima(down_short_hemisp_max)
• Shortwave Direct Normal Irradiance, Pyrheliometer(short_direct_normal)
• PSP shaded maximum(psps_max)

NSA/SKYRAD/C1 - Summer solstice shading of radiometers

On and around the summer solstice, the NIP (Direct Normal shortwave measurement) and PSP 
(global hemispheic shortwave measurement) radiometers are shaded by other instruments or 
support structures.  Shading azimuths have been determined for this site.  The radiometer 
mentor suggests not using the data from the NIP and PSP radiometers when the sun is 
within the following azimuth bounds (typically from May 8th to August 5th of each year):
Instrmt Obstruction     AzStart     AzEnd     
NIP     rad table       346         358
NIP     met tower       13          15
PSP     mfrsr           6           16

• Shortwave Direct Normal Irradiance, Pyrheliometer, Standard Deviation(short_direct_normal_std)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Maxima(down_short_hemisp_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer(down_short_hemisp)
• NIP maximum(nip_max)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Standard
  Deviation(down_short_hemisp_std)
• NIP standard deviation(nip_sd)
• NIP minimum(nip_min)
• PSP1 unshaded minimum(psp1_min)
• PSP shaded maximum(psps_max)
• Shortwave Direct Normal Irradiance, Pyrheliometer(short_direct_normal)
• NIP mean(nip_mean)
• PSP shaded minimum(psps_min)
• Downwelling Shortwave Hemispheric Irradiance, Ventilated Pyrgeometer, Minima(down_short_hemisp_min)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• PSP shaded mean(psps_mean)
• PSP1 unshaded maximum(psp1_max)
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• PSP1 unshaded standard deviation(psp1_sd)
• PSP shaded standard deviation(psps_sd)
• PSP1 unshaded mean(psp1_mean)