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

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.

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

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)
• Standard Deviation of 20m Calculated Vapor Pressure(VP20M_STD)
• 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)

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

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

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 Calculated Vapor Pressure(VP2M_AVG)
• Standard Deviation of 2m Calculated Dew Point(DP2M_STD)
• 2m Average Relative Humidity(RH2M_AVG)
• Standard Deviation of 2m Relative Humidity(RH2M_STD)
• 2m Average QLI Input Voltage(Volt2M_AVG)
• 2m Vector Averaged Wind Speed(WS2M_U_WVT)
• 2m Average Temperature(T2M_AVG)
• Standard Deviation of 2m Calculated Vapor Pressure(VP2M_STD)
• Standard Deviation of 2m Temperature(T2M_STD)
• 2m Average QLI Reference Temperature(RefT2M_AVG)
• 2m Average Calculated Dew Point(DP2M_AVG)
• 2m Arithmetic Mean Wind Speed(WS2M_S_WVT)
• 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 Relative Humidity(CMHRH)
• Chilled Mirror Dew Point(CMHDP)
• Chilled Mirror Temperature(CMHTemp)
• Chilled Mirror Calculated Saturation Vapor Pressure(SatVPCMH)