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/GNDRAD/C1 - Frosting/Condensation

The GNDRAD PIR and IRT comparison was showing the IRT 2-4 W/m^2 greater than the PIR.  
Suspected snow or frost on the instrument(s).  Corrective maintenance performed 10/15/04 at 
21:30 UT.  Optics of both instruments were cleaned.  Upwelling longwave measurement 
agreement restored (+/- 5 W/^2).

Although the relative performance (agreement) of the two instruments improved after 
corrective maintenance (+/- 2 W/m^2), no correction is suggested because the agreement remains 
with the estimated measurement uncertainty of +/- 4 W/m^2 (IRT) and +/-10 W/m^2 (Inverted 
PIR)

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

• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer,
  Standard Deviation(up_long_hemisp_std)
• Net Radiation, Standard Deviation(net_std)
• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer,
  Minima(up_long_hemisp_min)
• Surface Infra-Red Temperature Maxima(sfc_ir_temp_max)
• Effective Surface (Skin) Temperature(sfc_ir_temp)
• Surface Infra-Red Temperature Minima(sfc_ir_temp_min)
• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer,
  Maxima(up_long_hemisp_max)
• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer(up_long_hemisp)
• Surface Infra-Red Temperature, Standard Deviation(sfc_ir_temp_std)

• Instantaneous Upwelling Pyrgeometer Dome Thermistor Resistance, Pyrgeometer(inst_up_long_dome_resist)
• Instantaneous Upwelling Pyrgeometer Case Thermistor Resistance, Pyrgeometer(inst_up_long_case_resist)
• Instantaneous Upwelling Pyrgeometer Thermopile Voltage, Pyrgeometer(inst_up_long_hemisp_tp)
• Instantaneous PIR1 uncorrected irradiance(pir1_voltage)
• Instantaneous PIR1 dome thermistor(pir1_dome_therm)
• Instantaneous PIR1 case thermistor(pir1_case_therm)

NSA/MWRP/C1 - Missing data

Data are missing and unrecoverable.

• Raw data stream - documentation not supported(raw)

• Expected root-mean-square error in liquid water path retrieval(liquidWaterPathRmsError)
• Derived relative humidity(relativeHumidity)
• Internal blackbody reference temperature(blackbodyTemperature)
• Expected root-mean-square error in temperature retrieval(temperatureRmsError)
• Retrieved liquid water path(liquidWaterPath)
• Surface pressure at instrument(surfacePressure)
• atmospheric pressure at mean sea level and at tropopause (NGM250 predicted)(pressure)
• Retrieved liquid water path using only 23.835 and 30.0 GHz(liquidWaterPath2)
• Data quality flags(dataQualityFlags)
• Surface water vapor density at instrument(surfaceWaterVaporDensity)
• Derived virtual temperature(virtualTemperature)
• Expected root-mean-square error in water vapor density retrieval(waterVaporDensityRmsError)
• Equilibrium level pressure(equilibriumLevelPres)
• Time offset from base_time(base_time)
• Zenith-pointing infrared temperature at 10um(infraredTemperature)
• Height of bins above ground level for the temperature, retrieved water vapor,
  and pressure profile(height)
• north latitude for all the input platforms.(lat)
• altitude above sea levelaltunits(alt)
• Retrieved total precipitable water vapor(totalPrecipitableWater)
• Interpolated dewpoint temperature(dewpointTemperature)
• Solar azimuth referenced to the Central Facility.(azimuth)
• Cloud-base height, from Micropulse LIDAR or Belfort LIDAR ceilometer(cloudBaseHeight)
• Expected root-mean-square error in precipitable water retrieval using only
  23.835 and 30.0 GHz(totalPrecipitableWater2RmsError)
• Expected root-mean-square error in precipitable water retrieval(totalPrecipitableWaterRmsError)
• Elevation angle of Beam 0(elevation)
• Lifting condensation level pressure(liftingCondensationLevelPres)
• Level of free convection pressure(levelFreeConvectionPres)
• Retrieved water vapor density(waterVaporDensity)
• east longitude for all the input platforms.(lon)
• Retrieved total precipitable water vapor using only 23.835 and 30.0 GHz(totalPrecipitableWater2)
• Microwave brightness temperature(brightnessTemperature)
• Frequency(frequency)
• Convective available potential energy(cape)
• Flag indicating moisture sensor status(wetWindowFlag)
• Expected root-mean-square error in liquid water content retrieval(liquidWaterContentRmsError)
• Lifting condensation level(liftingCondensationLevel)
• Level of free convection(levelFreeConvection)
• Temperature used to determine the backscatter profile(temperature)
• Surface absolute temperature at instrument(surfaceTemperature)
• Expected root-mean-square error in liquid water path retrieval using only 23.835
  and 30.0 GHz(liquidWaterPath2RmsError)
• Retrieved cloud liquid water content(liquidWaterContent)
• Time offset of tweaks from base_time(time_offset)
• Surface relative humidity at instrument(surfaceRelativeHumidity)
• Interpolated water vapor mixing ratio(waterVaporMixingRatio)
• Time offset from midnight of date of file. For CO data, this is identical to
  time_offset and is included for compatibility.(time)
• Equilibrium level(equilibriumLevel)

NSA/SKYRAD/C1 - Reprocess: Incorrect datalogger program affecting PIR1 and PIR2 
downwelling longwave

The excitation delays using in measuring the PIR1 case thermistor commonly named "Case1" 
and the PIR2 dome thermistor called "Dome2" were discovered to have been incorrectly set 
to 0 in the Skyrad datalogger program when the new CR23X based Skyrad loggers were 
installed.  The result of no delay in these measurements results in an error in the measured 
resistance of the thermistors, Case1 and Dome2 and thus the calculated PIR1 and PIR2 
irradiances.  The errors are inversely proportial to temperature.

Users can apply the temperature dependent irradiance corrections shown in the table below. 
 Recall that the reported uncertainty of PIRs is typically +-.25% to +-.5% or 1 to 2 
W/m2.  The error corrections become the same order of magnitude or larger than the 
instrument uncertainties at or below 260K or 9F. 

Correction Table for Skyrad (TWP and NSA) DIR1 and DIR2 Irradiance				
	DIR1	DIR1	DIR2	DIR2
T[F]	Tcase[K]	Correction[W/m2]	Tdome[K]	Correction[W/m2]
109.4	316.13	0.00	316.13	0.00
100.5	311.20	-0.15	311.20	0.12
93.2	307.14	-0.12	307.14	0.10
87.0	303.70	-0.10	303.70	0.08
81.6	300.70	-0.17	300.70	0.14
77.0	298.15	-0.22	298.15	0.18
59.4	288.35	-0.34	288.35	0.27
47.4	281.72	-0.23	281.72	0.18
38.5	276.74	-0.42	276.74	0.34
31.3	272.77	-0.48	272.77	0.38
25.4	269.48	-0.61	269.48	0.49
20.3	266.67	-0.67	266.67	0.54
16.0	264.25	-0.82	264.25	0.66
12.1	262.11	-0.98	262.11	0.79
8.7	260.19	-0.97	260.19	0.78
5.6	258.46	-1.07	258.46	0.86
2.7	256.89	-1.17	256.89	0.94
0.1	255.44	-1.33	255.44	1.07
-2.3	254.11	-1.41	254.11	1.13
-4.5	252.87	-1.43	252.87	1.15
-6.6	251.71	-1.52	251.71	1.22
-8.5	250.63	-1.63	250.63	1.31
-10.4	249.62	-1.73	249.62	1.39
-12.2	248.58	-1.79	248.58	1.44
-15.4	246.82	-1.93	246.82	1.55
-18.3	245.23	-2.05	245.23	1.65
-20.9	243.78	-2.22	243.78	1.78
-23.3	242.44	-2.36	242.44	1.89
-25.5	241.21	-2.58	241.21	2.07
-27.5	240.07	-2.65	240.07	2.13
-29.5	239.01	-2.75	239.01	2.21
-31.3	238.00	-3.02	238.00	2.42

• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer2, Maxima(down_long_hemisp_shaded2_max)
• 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 Longwave Hemispheric Irradiance, Shaded Pyrgeometer2(down_long_hemisp_shaded2)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer1, Standard
  Deviation(down_long_hemisp_shaded1_std)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer1, Maxima(down_long_hemisp_shaded1_max)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer2, Standard
  Deviation(down_long_hemisp_shaded2_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 Downwelling Pyrgeometer Thermopile, Shaded Pyrgeometer1(inst_down_long_hemisp_shaded1_tp)

NSA/SKYRAD/C1 - Reprocess: 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 are 
being reprocessing to remove the calibration bias.  Note, this also affected standard 
deviation, maximum and minimum data fields.

• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer1(down_long_hemisp_shaded1)
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer2(down_long_hemisp_shaded2)

NSA/GNDRAD/C1 - Reprocess: 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 are 
being reprocessing to remove the calibration bias.  Note, this also affected standard 
deviation, maximum and minimum data fields.

• Upwelling (10 meter) Longwave Hemispheric Irradiance, Ventilated Pyrgeometer(up_long_hemisp)