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.

• VPCMH
• CMHDP
• CMHTemp
• 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.

• Wind direction, vector-averaged, at 40-m height(WD40M_DU_WVT)
• 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.

• Wind direction, vector-averaged, at 40-m height(WD40M_DU_WVT)
• 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.

• PcpRate
• InstPwCod
• CumSnow
• Visibility, 10 minute average(AvgVis10m)
• PWSAlarm
• Visibility, 1 minute average(AvgVis1mi)
• PwCod15mi
• CumH2O
• 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.

• DP20M_STD
• Temperature, dew point, average, at 20-m height(DP20M_AVG)
• Pressure, vapor, at 20-m height(VP20M_AVG)
• RH20M_STD
• Relative humidity, average, at 20-m height(RH20M_AVG)
• 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.

• VPCMH
• SatVPCMH
• CMHDP
• CMHTemp
• 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.

• WD2M_SDU_WVT
• Wind direction, vector-averaged, at 2-m height(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.

• VPCMH
• SatVPCMH
• CMHDP
• CMHTemp
• CMHRH

NSA/METTWR/C1 - 2m Datalogger Failed

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

• WD2M_SDU_WVT
• Relative humidity, average, at 2-m height(RH2M_AVG)
• Wind speed, mean, at 2-m height(WS2M_S_WVT)
• T2M_STD
• DP2M_STD
• Temperature, air, average, at 2-m height(T2M_AVG)
• Temperature, dew point, average, at 2-m height(DP2M_AVG)
• RH2M_STD
• Wind speed, vector-averaged, at 2-m height(WS2M_U_WVT)
• RefT2M_AVG
• VP2M_STD
• Volt2M_AVG
• Pressure, vapor, at 2-m height(VP2M_AVG)
• Wind direction, vector-averaged, at 2-m height(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.

• VPCMH
• SatVPCMH
• CMHDP
• CMHTemp
• 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.

• WD2M_SDU_WVT
• Relative humidity, average, at 2-m height(RH2M_AVG)
• Wind speed, mean, at 2-m height(WS2M_S_WVT)
• T2M_STD
• DP2M_STD
• Temperature, air, average, at 2-m height(T2M_AVG)
• Temperature, dew point, average, at 2-m height(DP2M_AVG)
• RH2M_STD
• Wind speed, vector-averaged, at 2-m height(WS2M_U_WVT)
• RefT2M_AVG
• VP2M_STD
• Volt2M_AVG
• Pressure, vapor, at 2-m height(VP2M_AVG)
• Wind direction, vector-averaged, at 2-m height(WD2M_DU_WVT)