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

NSA/METTWR/C1 - CMH Data missing

CMH dew point and temp data was missing. Since Dew Point and Temp data missing RH% value = 
100% during outage.  Corrosion on power plug was athe problem.

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

NSA/METTWR/C1 - Ultrasonic Wind Sensor Values Incorrect

The values collected from the ultrasonic wind sensor were intermittently incorrect.  Heavy 
wet snow during blizzard condition was interfering with the ultrasonic readings.

• Standard Deviation of Sonic Vector Averaged Wind Direction(SonicWD_SDU_WVT)
• Sonic Vector Averaged Wind Speed(SonicWS_U_WVT)
• Sonic Arithmetic Mean Wind Speed(SonicWS_S_WVT)
• Average Sonic Static Speed of Sound(SonicS_AVG)
• Average Y Component of Sonic Wind Speed(SonicY_AVG)
• Sonic Vector Averaged Wind Direction(SonicWD_DU_WVT)
• Average X Component of Sonic Wind Speed(SonicX_AVG)

NSA/METTWR/C1 - PWS data missing due to blizzard

PWS was offline and data was missing.  A blizzard consisting of heavy wet snow and strong 
winds caused snow impaction in the optics.  The PWS reported missing data as it was 
unable to measure anything meaningful.

• Precipitation Rate(PcpRate)
• Instant Present Weather Code(InstPwCod)
• Cumulative Snow Sum(CumSnow)
• 10 minute Average Visibility(AvgVis10m)
• Present Weather Sensor Alarm(PWSAlarm)
• 1 minute Average Visibility(AvgVis1mi)
• 15 minute Present Weather Code(PwCod15mi)
• 1 hour Present Weather Code(PwCod1hr)

NSA/METTWR/C1 - 2m Wind Speed Artificially Low

The 2m wind speed values were artificially low due to snow impaction during a heavy 
blizzard.  The cup anemometer heaters could not keep up with the rapid deposition of snow.

• 2m Arithmetic Mean Wind Speed(WS2M_S_WVT)
• 2m Vector Averaged Wind Speed(WS2M_U_WVT)

NSA/METTWR/C1 - CMH temp inaccurate

The CMH Temperature was consistently 4-7 degrees warmer than the 2M, 40M, 20M, and 10M 
temp. Intake fan failure; fan was replaced.

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

NSA/METTWR/C1 - 10m Wind Speed Low

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

• 10m Vector Averaged Wind Speed(WS10M_U_WVT)
• 10m Arithmetic Mean Wind Speed(WS10M_S_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 Vector Averaged Wind Speed(WS10M_U_WVT)
• 10m Arithmetic Mean Wind Speed(WS10M_S_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 Arithmetic Mean Wind Speed(WS40M_S_WVT)
• 40m Vector Averaged Wind Speed(WS40M_U_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 - CMH Data Missing

CMH data was missing due to it being removed for maintenance.

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

NSA/METTWR/C1 - CMH Data Suspect

CMH data was suspect due to incorrect calibration caused by procedural errors.  The 
procedures were corrected and a new calibration completed.

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

NSA/METTWR/C1 - Wind direction measurements suspect

20m wind direction standard deviation was 0 degrees for extended periods of time.  This 
suggests the wind vane was icing up.

• 20m Vector Averaged Wind Direction(WD20M_DU_WVT)
• Standard Deviation of 20m Vector Averaged Wind Direction(WD20M_SDU_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)

NSA/METTWR/C1 - Present Weather Sensor data missing or incorrect due to calibration.

The Present Weather Sensor data was missing or incorrect due to calibration checks.

• Precipitation Rate(PcpRate)
• Instant Present Weather Code(InstPwCod)
• Cumulative Snow Sum(CumSnow)
• 10 minute Average Visibility(AvgVis10m)
• Present Weather Sensor Alarm(PWSAlarm)
• 1 minute Average Visibility(AvgVis1mi)
• 15 minute Present Weather Code(PwCod15mi)
• Cumulative Water Sum(CumH2O)
• 1 hour Present Weather Code(PwCod1hr)

NSA/METTWR/C1 - All data from 10m Level Missing

The winch that lowers the tower booms failed.  Manual testing of the motor and winch 
allowed the booms to be lowered briefly and then raised back into position.  A heavy freezing 
rain/icing event added extra weight to the booms.  This extra weight was suspected as the 
cause as to why the 10m boom became disconnected.  After a new motor was installed and 
all booms were lowered and re-raised the 10m level came back on line.

• 10m Average Calculated Vapor Pressure(VP10M_AVG)
• Standard Deviation of 10m Relative Humidity(RH10M_STD)
• Standard Deviation of 10m Temperature(T10M_STD)
• 10m Arithmetic Mean Wind Speed(WS10M_S_WVT)
• 10m Vector Averaged Wind Direction(WD10M_DU_WVT)
• Standard Deviation of 10m Calculated Vapor Pressure(VP10M_STD)
• Standard Deviation of 10m Calculated Dew Point(DP10M_STD)
• Standard Deviation of 10m Vector Averaged Wind Direction(WD10M_SDU_WVT)
• 10m Average Calculated Dew Point(DP10M_AVG)
• 10m Vector Averaged Wind Speed(WS10M_U_WVT)
• 10m Average QLI Reference Temperature(RefT10m_AVG)
• 10m Average Relative Humidity(RH10M_AVG)
• 10m Average Temperature(T10M_AVG)
• 10m Average QLI Input Voltage(Volt10M_AVG)

NSA/METTWR/C1 - Missing CMH data

CMH data are missing.  Corrosion in the serial data line connections caused a loss of 
communication with the CMH.

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

NSA/METTWR/C1 - 10m level loss of power

The 10 meter instrument level lost power so all variables from this level are missing.

• 10m Average Calculated Vapor Pressure(VP10M_AVG)
• Standard Deviation of 10m Relative Humidity(RH10M_STD)
• Standard Deviation of 10m Temperature(T10M_STD)
• 10m Arithmetic Mean Wind Speed(WS10M_S_WVT)
• 10m Vector Averaged Wind Direction(WD10M_DU_WVT)
• Standard Deviation of 10m Calculated Vapor Pressure(VP10M_STD)
• Standard Deviation of 10m Calculated Dew Point(DP10M_STD)
• Standard Deviation of 10m Vector Averaged Wind Direction(WD10M_SDU_WVT)
• 10m Average Calculated Dew Point(DP10M_AVG)
• 10m Vector Averaged Wind Speed(WS10M_U_WVT)
• 10m Average QLI Reference Temperature(RefT10m_AVG)
• 10m Average Relative Humidity(RH10M_AVG)
• 10m Average Temperature(T10M_AVG)
• 10m Average QLI Input Voltage(Volt10M_AVG)

NSA/METTWR/C1 - 2m T/RH probe aspirator fan failed

The aspirator fan for the 2m level T/RH probe failed.  This caused higher than normal 
readings for temp and RH and artificially smoothed the data.

• 2m Average Calculated Dew Point(DP2M_AVG)
• 2m Average Temperature(T2M_AVG)
• Standard Deviation of 2m Relative Humidity(RH2M_STD)
• 2m Average Relative Humidity(RH2M_AVG)
• Standard Deviation of 2m Calculated Dew Point(DP2M_STD)
• Standard Deviation of 2m Temperature(T2M_STD)
• Standard Deviation of 2m Calculated Vapor Pressure(VP2M_STD)
• 2m Average Calculated Vapor Pressure(VP2M_AVG)

NSA/METTWR/C1 - Wind direction sensor frozen

After a power outage the 40m wind direction sensor was frozen.  Data from this sensor was 
not representative of the true winds.

• 40m Vector Averaged Wind Direction(WD40M_DU_WVT)
• Standard Deviation of 40m Vector Averaged Wind Direction(WD40M_SDU_WVT)

NSA/METTWR/C1 - CMH Sensor Calibrated Incorrectly

The CMH temp and DP were higher than the co-located T/RH probe at the 2m level.  An 
incorrect calibration along with a failing thermistor caused the readings to be incorrect for 
both measured values Temp and Dew Point.

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

NSA/METTWR/C1 - 40m wind sensor heater failure

The 40m wind direction became frozen at times.  The values from the sensor were flat-lined 
(stdev = 0) much of the time and did not match sensors from other levels.

• 40m Vector Averaged Wind Direction(WD40M_DU_WVT)
• Standard Deviation of 40m Vector Averaged Wind Direction(WD40M_SDU_WVT)

NSA/METTWR/C1 - 40m Wind Direction Data Suspect

The 40m wind direction data was suspect due to icing on the vane or a failing shafter 
heater or a combination of both.  The affected data can be easily seen on comparison plots 
with other levels data or by checking the standard deviation of the 40m wind direction.  
Any standard deviation of less than 0.10 degrees for the 40m level suggest a sluggish/ice 
affected sensor.

• 40m Vector Averaged Wind Direction(WD40M_DU_WVT)
• Standard Deviation of 40m Vector Averaged Wind Direction(WD40M_SDU_WVT)

NSA/METTWR/C1 - PWS Data Questionable

There was a degradation in the PWS lenses.  New lenses were installed on 08/28/2007 but a 
proper calibration was not conducted until 10/10/2007.  Data  during the listed time 
period should be used with caution.

• Precipitation Rate(PcpRate)
• Instant Present Weather Code(InstPwCod)
• Cumulative Snow Sum(CumSnow)
• 10 minute Average Visibility(AvgVis10m)
• Present Weather Sensor Alarm(PWSAlarm)
• 1 minute Average Visibility(AvgVis1mi)
• 15 minute Present Weather Code(PwCod15mi)
• Cumulative Water Sum(CumH2O)
• 1 hour Present Weather Code(PwCod1hr)

NSA/METTWR/C1 - 20m RH Data Questionable

The 20m RH data was questionable at times.  When the data appeared to be poor was when the 
2m and 20m agreed better than the 20m and the 40m and/or 10m.

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

NSA/METTWR/C1 - Intermittent missing data

Intermittent failure of the CMH to communicate with the logging system occurred on a daily 
basis.  This problem occurred anywhere from 4 to 8 hrs.  Problem began after maintenance 
to replace failing aspirator fan on 03/13/2008.

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

NSA/METTWR/C1 - 2m Wind Direction Sensor Freezing

The 2m wind direction was failing.  It began to exhibit instances of no movement 
suggesting it was frozen.  After some time it began to make erratic measurements compared to the 
co-located Ultrasonic and compared to the directions at the other levels.

• Standard Deviation of 2m Vector Averaged Wind Direction(WD2M_SDU_WVT)
• 2m Vector Averaged Wind Direction(WD2M_DU_WVT)

NSA/METTWR/C1 - CMH Intake Fan Failure

The CMH intake fan failed causing the dew point and temp data to be incorrect.

If users need only T/RH and derived variables they can use the 2m data collected using the 
HMP-45D probes.  CMH data are unrecoverable.

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

NSA/METTWR/C1 - 2m Datalogger Failed

The 2m temperature, wind speed, wind direction, and relative humidity were reporting the 
missing value (-9999).

• Standard Deviation of 2m Vector Averaged Wind Direction(WD2M_SDU_WVT)
• 2m Average Relative Humidity(RH2M_AVG)
• 2m Arithmetic Mean Wind Speed(WS2M_S_WVT)
• Standard Deviation of 2m Temperature(T2M_STD)
• Standard Deviation of 2m Calculated Dew Point(DP2M_STD)
• 2m Average Temperature(T2M_AVG)
• 2m Average Calculated Dew Point(DP2M_AVG)
• Standard Deviation of 2m Relative Humidity(RH2M_STD)
• 2m Vector Averaged Wind Speed(WS2M_U_WVT)
• 2m Average QLI Reference Temperature(RefT2M_AVG)
• Standard Deviation of 2m Calculated Vapor Pressure(VP2M_STD)
• 2m Average QLI Input Voltage(Volt2M_AVG)
• 2m Average Calculated Vapor Pressure(VP2M_AVG)
• 2m Vector Averaged Wind Direction(WD2M_DU_WVT)

NSA/METTWR/C1 - CMH required Calibration

The Chilled Mirror was showing some signs of being out of calibration.  Temperatures were 
at times higher than co-located temp probes and the dew point temperature values at times 
were not consistent with co-located RH sensors.

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

NSA/METTWR/C1 - 2m level data incorrect

The 2m data for temp, RH, dew point, wind speed wind direction & vapor pressure were 
incorrect.  The voltage values for the datalogger at that level were reporting as 60V with 
excursions to 100V.  These values should have damaged the logger at that level.  After an 
extended power outage on 08/04 the data all became reasonable. There is no explanation as 
to the cause of this failure.

• Standard Deviation of 2m Vector Averaged Wind Direction(WD2M_SDU_WVT)
• 2m Average Relative Humidity(RH2M_AVG)
• 2m Arithmetic Mean Wind Speed(WS2M_S_WVT)
• Standard Deviation of 2m Temperature(T2M_STD)
• Standard Deviation of 2m Calculated Dew Point(DP2M_STD)
• 2m Average Temperature(T2M_AVG)
• 2m Average Calculated Dew Point(DP2M_AVG)
• Standard Deviation of 2m Relative Humidity(RH2M_STD)
• 2m Vector Averaged Wind Speed(WS2M_U_WVT)
• 2m Average QLI Reference Temperature(RefT2M_AVG)
• Standard Deviation of 2m Calculated Vapor Pressure(VP2M_STD)
• 2m Average QLI Input Voltage(Volt2M_AVG)
• 2m Average Calculated Vapor Pressure(VP2M_AVG)
• 2m Vector Averaged Wind Direction(WD2M_DU_WVT)