QUALITY CONTROL

Quality Control (QC) procedures are required to ensure that the data collected meet standards of reliability and accuracy. Here, the quality control can be defined as the operational procedures that will be routinely followed during the normal operation of the monitoring system to ensure that a measurement process is working properly. These procedures include periodic calibration of the instruments, site inspections, data screening, data validation, and preventive maintenance.

In this guideline, we will follow the data screening as QC procedure. The screening procedures generally include comparisons of measured values to upper and lower limits; these may be physical limits, such as an instrument threshold, or may be established based on experience or historical data. The suggested screening criteria are listed below:

Variable Screening Criteria: Flag data if the value
Wind Speed
  • - is less than zero or greater than 25 m/s
  • - does not vary by more than 0.1 m/s for 3 consecutive hours
  • - does not vary by more than 0.5 m/s for 12 consecutive hours
Wind Direction
  • - is less than zero or greater than 360 degrees
  • - does not vary by more than 1 degree for more than 3 consecutive hours
  • - does not vary by more than 10 degrees for 18 consecutive hours
Temperature
  • - is greater than the local record high
  • - is less than the local record low (The above limits could be applied on a monthly basis.)
  • - is greater than a 5oC change from the previous hour
  • - does not vary by more than 0.5oC for 12 consecutive hours
Temperature Difference
  • - is greater than 0.10C/m during the daytime
  • - is less than -0.10C/m during the night time
  • - is greater than 5.00C or less than -3.00C
Dew Point Temperature
  • - is greater than the ambient temperature for the given time period
  • - is greater than a 50C change from the previous hour
  • - does not vary by more than 0.50C for 12 consecutive hours
  • - equals the ambient temperature for 12 consecutive hours
Precipitation
  • - is greater than 25 mm in one hour
  • - is greater than 100 mm in 24 hours
  • - is less than 50 mm in three months
  • (The above values can be adjusted based on local climate.)
Pressure
  • - is greater than 1060 millibar (sea level)
  • - is less than 940 millibar (sea level)
  • (The above values should be adjusted for elevations other than sea level.)
  • - changes by more than 6 millibar in three hours
Radiation
  • - is greater than zero at night
  • - is greater than the maximum possible for the date and latitude

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