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

NSA/METTWR/C1 - power outage at 40m level

40m level lost power so no data was collected from this level.

• Standard Deviation of 40m Temperature(T40M_STD)
• Standard Deviation of 40m Calculated Vapor Pressure(VP40M_STD)
• 40m Average QLI Reference Voltage(Volt40M_AVG)
• 40m Vector Averaged Wind Direction(WD40M_DU_WVT)
• Standard Deviation of 40m Vector Averaged Wind Direction(WD40M_SDU_WVT)
• 40m Arithmetic Mean Wind Speed(WS40M_S_WVT)
• 40m Average Temperature(T40M_AVG)
• Standard Deviation of 40m Calculated Dew Point(DP40M_STD)
• 40m Average Relative Humidity(RH40M_AVG)
• 40m Average Calculated Dew Point(DP40M_AVG)
• 40m Average Calculated Vapor Pressure(VP40M_AVG)
• Standard Deviation of 40m Relative Humidity(RH40M_STD)
• 40m Vector Averaged Wind Speed(WS40M_U_WVT)
• 40m Average QLI Reference Temperature(RefT40M_AVG)

NSA/METTWR/C1 - CMH Dew Point and RH data Incorrect

The Chilled Mirror Dew Point reported negative dew point values.  This caused the RH to be 
much lower than reality also.  Compared to the 2m level the RH and dew point from the 
CMH are incorrect.  Mirror was dirty, it was removed, cleaned and recalibrated.

• Chilled Mirror Calculated Relative Humidity(CMHRH)
• Chilled Mirror Dew Point(CMHDP)

NSA/METTWR/C1 - 20m Temperature/RH Sensor Failing

The 20m temperature and RH sensor began reading high on 20040719.
Aspirator fan failure caused a portion of the high reading.  New fan
failed to correct for all errors.  Sensor replaced on 20040908 with
recently calibrated sensor.

• Standard Deviation of 20m Calculated Dew Point(DP20M_STD)
• Standard Deviation of 20m Calculated Vapor Pressure(VP20M_STD)
• 20m Average Temperature(T20M_AVG)
• Standard Deviation of 20m Relative Humidity(RH20M_STD)
• 20m Average Relative Humidity(RH20M_AVG)
• 20m Average Calculated Vapor Pressure(VP20M_AVG)
• 20m Average Calculated Dew Point(DP20M_AVG)
• Standard Deviation of 20m Temperature(T20M_STD)

NSA/METTWR/C1 - Incorrect Maximum for Precip Values

The max values for cumulative rain sum of 99 mm and the rain rate of 999 mm/hr are 
incorrect.  In communication with the manufacturer it has been found that the manual was in 
error.  The actual max values of the cumulative rain sum is 99.99 mm and the rain rate is 
999.99 mm/hr.

• Precipitation Rate(PcpRate)
• Cumulative Water Sum(CumH2O)

NSA/METTWR/C1 - Data 1-minute behind

Data from the Barometer, Chilled Mirror Hygrometer and the Present Weather Sensor were 
one-minute behind due to timing problems collecting data from the Serial Data Multiplexer 
that handled these sensors.

• 15 minute Present Weather Code(PwCod15mi)
• 1 minute Average Visibility(AvgVis1mi)
• Chilled Mirror Dew Point(CMHDP)
• Instant Present Weather Code(InstPwCod)
• Chilled Mirror Calculated Saturation Vapor Pressure(SatVPCMH)
• Chilled Mirror Calculated Relative Humidity(CMHRH)
• Chilled Mirror Calculated Vapor Pressure(VPCMH)
• 1 hour Present Weather Code(PwCod1hr)
• Cumulative Snow Sum(CumSnow)
• 10 minute Average Visibility(AvgVis10m)
• Chilled Mirror Temperature(CMHTemp)
• Precipitation Rate(PcpRate)
• Cumulative Water Sum(CumH2O)
• Present Weather Sensor Alarm(PWSAlarm)
• Atmospheric Pressure(AtmPress)

NSA/SKYRAD/C1 - IRT failure

The IRT failed and was replaced with a spare.

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

NSA/METTWR/C1 - Reprocess: Wind direction data incorrect

Wind direction data is off by 30 degrees for all wind sensors.  The 40-m tower was 
misaligned to true north.

• 40m Vector Averaged Wind Direction(WD40M_DU_WVT)
• 2m Vector Averaged Wind Direction(WD2M_DU_WVT)
• 20m Vector Averaged Wind Direction(WD20M_DU_WVT)
• Sonic Vector Averaged Wind Direction(SonicWD_DU_WVT)
• 10m Vector Averaged Wind Direction(WD10M_DU_WVT)

NSA/METTWR/C1 - CMH Data Not Representative

The intake of the CMH was blocked with hoar frost.  The temperatures measured by the 
chilled mirror and the temperature probe were not representative of the ambient conditions as 
a result.  The RH data calculated from these values is incorrect also.

• Chilled Mirror Calculated Vapor Pressure(VPCMH)
• Chilled Mirror Calculated Relative Humidity(CMHRH)
• Chilled Mirror Dew Point(CMHDP)
• Chilled Mirror Temperature(CMHTemp)
• Chilled Mirror Calculated Saturation Vapor Pressure(SatVPCMH)

NSA/METTWR/C1 - 10m Wind Speed Low

The 10m wind speed values are too low due to ice accumulation on the cup anemometer.

• 10m Arithmetic Mean Wind Speed(WS10M_S_WVT)
• 10m Vector Averaged Wind Speed(WS10M_U_WVT)

NSA/METTWR/C1 - 10m Wind Speed Intermittently Low

The 10m wind speeds are intermittently too low due to ice accumulation on the cup 
anemometer.

• 10m Arithmetic Mean Wind Speed(WS10M_S_WVT)
• 10m Vector Averaged Wind Speed(WS10M_U_WVT)

NSA/METTWR/C1 - 40m Wind Speeds Intermittently Low

The 40m wind speed values were too low due to ice accumulation on the cup anemometer.

• 40m Vector Averaged Wind Speed(WS40M_U_WVT)
• 40m Arithmetic Mean Wind Speed(WS40M_S_WVT)

NSA/METTWR/C1 - 20m Wind Speeds Intermittently Low

The 20m wind speeds were artificially low due to ice accumulation on the cup anemometer.

• 20m Vector Averaged Wind Speed(WS20M_U_WVT)
• 20m Arithmetic Mean Wind Speed(WS20M_S_WVT)

NSA/METTWR/C1 - Reprocess: Barometric Data Changed from hPa to kPa

Barometric pressure data was converted from hPa to kPa in order to standardize the 
measurement units among ARM sites and to conform to accepted standard units determined by the 
scientific community.

• Atmospheric Pressure(AtmPress)