TWP/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 absolute value of the errors are inversely proportial to temperature.

Users can apply 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. 

Irradiance 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

• inst_down_long_shaded1_dome_resist
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer1)(inst_down_long_hemisp_shaded1_tp)
• inst_down_long_shaded1_case_resist
• inst_down_long_shaded2_case_resist
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer2)(inst_down_long_hemisp_shaded2_tp)
• inst_down_long_shaded2_dome_resist

• down_long_hemisp_shaded2_min
• down_long_hemisp_shaded2_std
• down_long_hemisp_shaded1_min
• down_long_hemisp_shaded2_max
• down_long_hemisp_shaded1_std
• Irradiance, longwave, downwelling, hemispheric, shaded pyrgeometer2(down_long_hemisp_shaded2)
• down_long_hemisp_shaded1_max
• Irradiance, longwave, downwelling, hemispheric, shaded pyrgeometer1(down_long_hemisp_shaded1)

TWP/SKYRAD/C2 - 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 absolute value of 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.
 
Irradiance 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

• down_long_hemisp_shaded1_max
• down_long_hemisp_shaded2_min
• down_long_hemisp_shaded1_std
• down_long_hemisp_shaded1_min
• down_long_hemisp_shaded2_std
• down_long_hemisp_shaded2_max
• Irradiance, longwave, downwelling, hemispheric, shaded pyrgeometer2(down_long_hemisp_shaded2)
• Irradiance, longwave, downwelling, hemispheric, shaded pyrgeometer1(down_long_hemisp_shaded1)

• inst_down_long_shaded1_case_resist
• inst_down_long_shaded2_dome_resist
• inst_down_long_shaded1_dome_resist
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer1)(inst_down_long_hemisp_shaded1_tp)
• inst_down_long_shaded2_case_resist
• Irradiance, longwave, downwelling, hemispheric, thermopile (Shaded Pyrgeometer2)(inst_down_long_hemisp_shaded2_tp)

TWP/SKYRAD/C2 - Short direct normal

The short_direct_normal (NIP) data are missing or incorrect due to instrument cable 
failure.  The cable was replaced.

The short_direct_normal can be calculated using the following relationship for shortwave 
radiometers:
global hemispheric = diffuse hemispheric + direct normal *cos (zenith angle)

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

• inst_direct_normal

TWP/SKYRAD/C2 - Reprocessed: Incorrect calibrations

The SKYRAD PSPs were changed out 11/25 but the datalogger program was not updated until 
11/30.

Reprocessed to correct calibration per:
  down_short_diffuse(corrected) = down_short_diffuse(orig) * (118.18/112.42)
  short_direct_normal(corrected)= short_direct_normal(orig) * (122.20/118.11)
  down_short_hemips(corrected) = down_short_hemisp(orig) * (133.16/137.57)

Reprocessing completed March 2008.

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

• inst_diffuse
• inst_direct_normal
• inst_global

TWP/SKYRAD/C1 - Failed PSP ventilator fan

On 1/31 the ventilator for the PSP measuring downwelling_shortwave_hemispheric irradiance 
failed.  The DQ effect of this failure on the measurement of down_short_hemisp is not 
possible to fully quantify but it has been noted that during these failures the PSP 
nighttime values can be several (1-3W/m2) smaller than usual.  Another effect is slower thermal 
response (1hr) of the PSP instrument due to daytime heating and cooling of the ventilator 
housing.

• inst_global

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

TWP/SKYRAD/C2 - Direct Normal reading too low

The NIP (direct_normal shortwave irradiance) measurement was reading too low during this 
time period.  No TWP Ops documentation could be found to determine the cause but data 
review indicate that the NIP appeared to be reading low by about 25W/m2 during this period.  
The NIP data had well defined steps in irradiance when compared to three component checks 
indicating the problem period.

• Raw data stream - documentation not supported

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

• inst_direct_normal

TWP/SKYRAD/C1 - Tracker Failure

The solar tracker at C1 failed to wake up the morning of 6/10 approximately 2000GMT. Ops 
discovered problem and reset tracker 6/12 approximately 0800GMT.

Tracker dependent instrument data is inaccurate - this includes the short_direct (NIP) and 
down_short_diffuse_hemisp (8-48). The down_short_hemisp (PSP) and down_long_hemisp (PIR) 
are unaffected.

• inst_diffuse
• inst_direct_normal

• Shortwave Direct Normal Irradiance, Pyrheliometer, Minima(short_direct_normal_min)
• Downwelling Shortwave Diffuse Hemisp. Irrad., Ventilated Pyranometer, Maxima(down_short_diffuse_hemisp_max)
• short_direct_normal_std
• Shortwave Direct Normal Irradiance, Pyrheliometer, Maxima(short_direct_normal_max)
• down_short_diffuse_hemisp_std
• Radiation, shortwave, direct normal irradiance, 1-min avg(short_direct_normal)
• 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)

TWP/MPL/C1 - Laser not transmitting

Laser was not turned on with remainder of system following power failure.

• Pressure, associated geometric height, at altitude, NGM model output(height)
• time
• dead_time_corrected
• nsamples_cross_pol_average
• range_bin_width
• max_altitude
• time_offset
• polarization_control_voltage_cross_pol
• alt
• detector_temp
• scope_temp
• nsamples_co_pol_average
• Attenuated backscatter, cross pol(signal_return_cross_pol)
• base_time
• Attenuated backscatter, copol(signal_return_co_pol)
• background_signal_std_cross_pol
• range
• shots_per_sample
• Preliminary cloud base height above ground level, cross-pol(preliminary_cbh_cross_pol)
• num_channels
• lon
• aqc_signal_return_cross_pol
• num_bins
• aqc_signal_return_co_pol
• energy_monitor
• range_bins
• background_signal_cross_pol
• lat
• background_signal_std_co_pol
• background_signal_co_pol
• laser_temp
• polarization_control_voltage_co_pol
• pulse_rep
• Preliminary cloud base height above ground level, co-pol(preliminary_cbh_co_pol)
• range_offset

• range
• Attenuated backscatter, copol(signal_return_co_pol)
• polarization_control_voltage_cross_pol
• laser_temp
• Preliminary cloud base height above ground level, cross-pol(preliminary_cbh_cross_pol)
• background_signal_std_co_pol
• dead_time_corrected
• range_offset
• time_offset
• time
• range_bin_width
• shots_per_sample
• Attenuated backscatter, cross pol(signal_return_cross_pol)
• num_channels
• nsamples_cross_pol_average
• Preliminary cloud base height above ground level, co-pol(preliminary_cbh_co_pol)
• alt
• detector_temp
• num_bins
• background_signal_cross_pol
• max_altitude
• Pressure, associated geometric height, at altitude, NGM model output(height)
• polarization_control_voltage_co_pol
• nsamples_co_pol_average
• lon
• lat
• pulse_rep
• background_signal_std_cross_pol
• energy_monitor
• base_time
• range_bins
• scope_temp
• aqc_signal_return_co_pol
• background_signal_co_pol
• aqc_signal_return_cross_pol

• dead_time_corrected
• signal_return
• num_bins
• num_channels
• range_bin_time
• alt
• Pressure, associated geometric height, at altitude, NGM model output(height)
• scope_temp
• time
• background_signal_std
• pulse_rep
• time_offset
• polarization_control
• range_bins
• range_bin_width
• range_offset
• energy_monitor
• lon
• max_altitude
• shots_per_avg
• detector_temp
• polarization_control_voltage
• range
• lat
• Preliminary cloud base height above ground level(preliminary_cbh)
• background_signal
• laser_temp
• base_time

TWP/SKYRAD/C1 - PIR2 ventilator fan failure

During the time range specified the PIR2 output is questionable due to ventilator fan 
failure. Although the PIR is temperature compensated, data review indicates that the PIR2 
didn't compare as well with PIR1. Typical differences during full sun are approximately 10 
w/m2. During this time period differences of 10-14 W/m2 were noted.

• inst_down_long_hemisp2_dome_resist
• inst_down_long_hemisp2_tp
• inst_down_long_hemisp2_case_resist

• down_long_hemisp2_max
• inst_down_long_hemisp2_tp
• inst_down_long_hemisp2_dome_temp
• down_long_hemisp2_std
• Downwelling Longwave Hemispheric Irradiance, Shaded Pyrgeometer2(down_long_hemisp2)
• inst_down_long_hemisp2_case_temp
• down_long_hemisp2_min

TWP/MPL/C1 - Missing data

Data are missing and unrecoverable.

• Pressure, associated geometric height, at altitude, NGM model output(height)
• time
• dead_time_corrected
• nsamples_cross_pol_average
• range_bin_width
• max_altitude
• time_offset
• polarization_control_voltage_cross_pol
• alt
• detector_temp
• scope_temp
• nsamples_co_pol_average
• Attenuated backscatter, cross pol(signal_return_cross_pol)
• base_time
• Attenuated backscatter, copol(signal_return_co_pol)
• background_signal_std_cross_pol
• range
• shots_per_sample
• Preliminary cloud base height above ground level, cross-pol(preliminary_cbh_cross_pol)
• num_channels
• lon
• aqc_signal_return_cross_pol
• num_bins
• aqc_signal_return_co_pol
• energy_monitor
• range_bins
• background_signal_cross_pol
• lat
• background_signal_std_co_pol
• background_signal_co_pol
• laser_temp
• polarization_control_voltage_co_pol
• pulse_rep
• Preliminary cloud base height above ground level, co-pol(preliminary_cbh_co_pol)
• range_offset

• range
• Attenuated backscatter, copol(signal_return_co_pol)
• polarization_control_voltage_cross_pol
• laser_temp
• Preliminary cloud base height above ground level, cross-pol(preliminary_cbh_cross_pol)
• background_signal_std_co_pol
• dead_time_corrected
• range_offset
• time_offset
• time
• range_bin_width
• shots_per_sample
• Attenuated backscatter, cross pol(signal_return_cross_pol)
• num_channels
• nsamples_cross_pol_average
• Preliminary cloud base height above ground level, co-pol(preliminary_cbh_co_pol)
• alt
• detector_temp
• num_bins
• background_signal_cross_pol
• max_altitude
• Pressure, associated geometric height, at altitude, NGM model output(height)
• polarization_control_voltage_co_pol
• nsamples_co_pol_average
• lon
• lat
• pulse_rep
• background_signal_std_cross_pol
• energy_monitor
• base_time
• range_bins
• scope_temp
• aqc_signal_return_co_pol
• background_signal_co_pol
• aqc_signal_return_cross_pol

• dead_time_corrected
• signal_return
• num_bins
• num_channels
• range_bin_time
• alt
• Pressure, associated geometric height, at altitude, NGM model output(height)
• scope_temp
• time
• background_signal_std
• pulse_rep
• time_offset
• polarization_control
• range_bins
• range_bin_width
• range_offset
• energy_monitor
• lon
• max_altitude
• shots_per_avg
• detector_temp
• polarization_control_voltage
• range
• lat
• Preliminary cloud base height above ground level(preliminary_cbh)
• background_signal
• laser_temp
• base_time

TWP/MPL/C2 - Laser transmitter off

The laser diode power supply was inadvertantly turned off by the operators. Upon correct 
restarting sequence, system returned to normal.

• aqc_signal_return_cross_pol
• num_bins
• lat
• Preliminary cloud base height above ground level, cross-pol(preliminary_cbh_cross_pol)
• range_offset
• Attenuated backscatter, copol(signal_return_co_pol)
• range
• background_signal_cross_pol
• Pressure, associated geometric height, at altitude, NGM model output(height)
• shots_per_sample
• laser_temp
• time
• nsamples_co_pol_average
• scope_temp
• range_bins
• polarization_control_voltage_co_pol
• aqc_signal_return_co_pol
• time_offset
• base_time
• Preliminary cloud base height above ground level, co-pol(preliminary_cbh_co_pol)
• detector_temp
• num_channels
• background_signal_co_pol
• polarization_control_voltage_cross_pol
• pulse_rep
• alt
• background_signal_std_co_pol
• Attenuated backscatter, cross pol(signal_return_cross_pol)
• lon
• energy_monitor
• nsamples_cross_pol_average
• range_bin_width
• max_altitude
• dead_time_corrected
• background_signal_std_cross_pol

• time_offset
• max_altitude
• aqc_signal_return_cross_pol
• Attenuated backscatter, cross pol(signal_return_cross_pol)
• polarization_control_voltage_cross_pol
• num_channels
• range
• background_signal_cross_pol
• Attenuated backscatter, copol(signal_return_co_pol)
• Preliminary cloud base height above ground level, co-pol(preliminary_cbh_co_pol)
• laser_temp
• lon
• detector_temp
• scope_temp
• base_time
• Pressure, associated geometric height, at altitude, NGM model output(height)
• shots_per_sample
• range_bin_width
• background_signal_std_co_pol
• background_signal_std_cross_pol
• dead_time_corrected
• polarization_control_voltage_co_pol
• range_offset
• alt
• nsamples_cross_pol_average
• energy_monitor
• range_bins
• pulse_rep
• num_bins
• time
• background_signal_co_pol
• nsamples_co_pol_average
• Preliminary cloud base height above ground level, cross-pol(preliminary_cbh_cross_pol)
• aqc_signal_return_co_pol
• lat

• lon
• detector_temp
• polarization_control
• range_bin_time
• max_altitude
• scope_temp
• Pressure, associated geometric height, at altitude, NGM model output(height)
• background_signal_std
• base_time
• signal_return
• shots_per_avg
• background_signal
• range_bins
• time
• range_bin_width
• time_offset
• dead_time_corrected
• num_channels
• num_bins
• laser_temp
• lat
• range
• polarization_control_voltage
• energy_monitor
• pulse_rep
• range_offset
• alt
• Preliminary cloud base height above ground level(preliminary_cbh)