Calibration.md

Calibration

Data from UUCON measurement sites with a Licor 6262 or Licor 7000 on-site are calibrated every 2 h using the three reference gases, while sites with a LGR UGGA are calibrated every 3 h. Since the Li-6262s are near linear through the range of atmospheric observations and calibration gases, each standard of known mole fraction is linearly interpolated between two consecutive calibration periods to represent the drift in the measured standards over time. Ordinary least squares regression is then applied to the interpolated reference values, and the linear coefficients are used to correct the observations. The linear slope, intercept, and fit statistics are returned for each observation for diagnostic purposes. See Bares et al., 2019 for more details.

Gas Identification

To differentiate data between atmospheric air and reference gas measurements, we use the following ID convention:

ID	Description
≥0	Reference gas measurement -- value indicates concentration
-10	Atmospheric air measurement
-99	System flush

Column naming conventions for calibrated data files

Licor 6262 IRGA

Column Name	Description
Time_UTC	Time in UTC
CO2d_ppm_cal	The calibrated concenctration of DRY CO2 in parts per million
CO2d_ppm_raw	The uncalibrated concentraion of DRY CO2 in parts per million
CO2d_m	The slope of the calibration applied
CO2d_b	The y-intercept of the calibration applied
CO2d_n	The number of calibration tanks used in the calibration applied
CO2d_rsq	The R^2 value derived from the slope of the calibration applied
CO2d_rmse	The root mean squared error value derived from the slope of the calibration applied
ID_CO2	ID of CO2 being measured (-10(ambient), -99(flushing), Standard tank concentration)
QAQC_Flag	Automated QC flagging. See table "QAQC flagging conventions"

Los Gatos Research UGGA

Column Name	Description
Time_UTC	Time in UTC
CO2d_ppm_cal	The calibrated concenctration of DRY CO2 in parts per million
CO2d_ppm_raw	The uncalibrated concentraion of DRY CO2 in parts per million
CO2d_m	The slope of the calibration for CO2
CO2d_b	The y-intercept of the calibration for CO2
CO2d_n	The number of calibration tanks used in the calibration for CO2
CO2d_rsq	The R^2 value derived from the slope of the calibration for CO2
CO2d_rmse	The root mean squared error value derived from the slope of the calibration for CO2
ID_CO2	ID of CO2 being measured (-10(ambient), -99(flushing), Standard tank concentration)
CH4d_ppm_cal	The calibrated concenctration of DRY CH4 in parts per million
CH4d_ppm_raw	The uncalibrated concentraion of DRY CH4 in parts per million
CH4d_m	The slope of the calibration for CH4
CH4d_b	The y-intercept of the calibration for CH4
CH4d_n	The number of calibration tanks used in the calibration for CH4
CH4d_rsq	The R^2 value derived from the slope of the calibration for CH4
CH4d_rmse	The root mean squared error value derived from the slope of the calibration for CH4
ID_CH4	ID of CH4 being measured (-10(ambient), -99(flushing), Standard tank concentration)
QAQC_Flag	Automated QC flagging. See table "QAQC flagging conventions"