SGP/THWAPS/B4 - Wind Data Suspect

Wind speed and direction data suspect during time period due to icing.

• Mean Wind Speed(wspd)
• Standard Deviation of Wind Direction(sd_wdir)
• Unit Vector Wind Direction(wdir)

SGP/THWAPS/B4 - Minor biases in humidity and saturation vapor pressure

The THWAPS humidity sensor output was scaled so that the instrument output voltage range 
(0-1VDC) represented 0-100 %RH. Comparisons with the co-located chilled mirror sensor at 
the CF suggested that the THWAPS RH sensor was reading artifically low at high humidities 
because of this 100 %RH maximum. 

The scaling of the system was changed so that 0-1 VDC now represents 0-110 %RH. This 
resulted in a slight loss of precision in the measurements, but since the RH measurement is 
only accurate to 2-3 %RH at best, this isn't a significant problem.

The saturation vapor correction when temps are below 0C contained an error in the 
multiplier.  The incorrect multiplier only equates to an error of 0.01 kPa which is less than the 
stated uncertainty of the measurement (+/- 0.035 kPa).

• Relative humidity inside the instrument enclosure(rh)
• Vapor Pressure (kiloPascals)(vap_pres)

SGP/THWAPS/B4 - RH values exceeding 105%

RH measurements were reaching the max value of 105% on a consistent basis.  Spider web 
internal to the sensor housing was found and removed.

• Relative humidity inside the instrument enclosure(rh)
• Standard Deviation of Vapor Pressure(sd_vap_pres)
• Vapor Pressure (kiloPascals)(vap_pres)
• Standard Deviation of Relative Humidity(sd_rh)

SGP/THWAPS/B4 - Time uncertainty

The clock on the site collection system was incorrect when it was deployed on 10/20.  The 
clock was corrected on 10/21 at approximately 15:02.  The data collected in the interim 
received grossly wrong time stamps.  These time stamps have been manually corrected, but 
there is some uncertainty in the time stamps still.

Data during the period specified should be considered to be within +/- 5 minutes of the 
timestamp indicated.

• Mean Wind Speed(wspd)
• Beam 0 Temperature(temp)
• Relative humidity inside the instrument enclosure(rh)
• Retrieved pressure profile(pres)
• base time(base_time)
• Vapor Pressure (kiloPascals)(vap_pres)
• Unit Vector Wind Direction(wdir)
• Time offset of tweaks from base_time(time_offset)

SGP/THWAPS/B4 - Temp and RH data incorrect

After sensor replacement the temperature values are too low.  The range of the sensor was 
incorrectly set at -40 to 80 instead of -30 to 70.  RH values are also suspect.

• Standard Deviation of Air Temperature(sd_temp)
• Beam 0 Temperature(temp)
• Relative humidity inside the instrument enclosure(rh)
• Standard Deviation of Vapor Pressure(sd_vap_pres)
• Vapor Pressure (kiloPascals)(vap_pres)
• Standard Deviation of Relative Humidity(sd_rh)

SGP/THWAPS/B4 - Reprocess: RH% values 9% High

After replacement of the THWAPS T/RH sensor the span was incorrectly set to 0-100 instead 
of 0-110.  This caused the RH values to be 9% higher than actual values.

• Relative humidity inside the instrument enclosure(rh)
• Vapor Pressure (kiloPascals)(vap_pres)

SGP/THWAPS/B4 - Wind Data Incorrect Due to Icing

An ice storm caused the wind data from the RM Young wind sensor to be
incorrect.  In many instances it was frozen and unmoving, at times it
measured values but those are extremely suspect.

• Mean Wind Speed(wspd)
• Standard Deviation of Wind Direction(sd_wdir)
• Unit Vector Wind Direction(wdir)

SGP/THWAPS/B4 - Temp and RH values incorrect during hours of no sunlight

Unknown issues caused the temp and RH values to become lower during non-sunlight hours.  
The affects are best seen at sunrise and sunset when the data would adjust upward or 
downward abruptly.  Plots of the standard deviation show abrupt spikes at these times.  
Comparison plots to nearby mesonet sites suggest the nighttime values of both temp and RH are 
lower than nearby sites.  This problem was also very intermittent and was not occurring on 
a daily basis.  A complete move of the sensors and collection system to a separate 
building repaired the problem.

• Standard Deviation of Pressure(sd_pres)
• Standard Deviation of Air Temperature(sd_temp)
• Beam 0 Temperature(temp)
• Relative humidity inside the instrument enclosure(rh)
• Standard Deviation of Vapor Pressure(sd_vap_pres)
• Vapor Pressure (kiloPascals)(vap_pres)
• Standard Deviation of Relative Humidity(sd_rh)