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 - Instrument problem, Contamination, False signal

Heavy, wet and blowing snow and ice caused measurement problems with the sonic anemometer 
mounted at the 2m level.  Erroneous readings caused both the wind speed and direction 
values to be reported anomolously.  Once the heavy, wet snow and ice stopped the readings 
returned to normal.

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

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/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 - 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)