TY - JOUR
T1 - Field Evaluation of Column CO2 Retrievals From Intensity-Modulated Continuous-Wave Differential Absorption Lidar Measurements During the ACT-America Campaign
AU - Campbell, Joel F.
AU - Lin, Bing
AU - Dobler, Jeremy
AU - Pal, Sandip
AU - Davis, Kenneth
AU - Obland, Michael D.
AU - Erxleben, Wayne
AU - McGregor, Doug
AU - O'Dell, Chris
AU - Bell, Emily
AU - Weir, Brad
AU - Fan, Tai Fang
AU - Kooi, Susan
AU - Gordon, Iouli
AU - Corbett, Abigail
AU - Kochanov, Roman
N1 - Publisher Copyright:
©2020. The Authors.
PY - 2020/12
Y1 - 2020/12
N2 - We present an evaluation of airborne intensity-modulated continuous-wave (IM-CW) lidar measurements of atmospheric column CO2 mole fractions during the Atmospheric Carbon and Transport–America (ACT-America) project. This lidar system transmits online and offline wavelengths simultaneously on the 1.57111-μm CO2 absorption line, with each modulated wavelength using orthogonal swept frequency waveforms. After the spectral characteristics of this system were calibrated through short-path measurements, we used the HITRAN spectroscopic database to calculate the average-column CO2 mole fraction (XCO2) from the lidar-measured optical depths. Using in situ measurements of meteorological parameters and CO2 concentrations for calibration data, we demonstrate that our lidar CO2 measurements were consistent from season to season and had an absolute calibration error (standard deviation) of 0.80 ppm when compared to XCO2 values calculated from in situ measurements. By using a 10-s or longer moving average, a precision of 1 ppm or better was obtained. The estimated CO2 measurement precision for 0.1-, 1-, 10-, and 60-s averages was determined to be 3.4, 1.2, 0.43, and 0.26 ppm, respectively. These correspond to measurement signal-to-noise ratios of 120, 330, 950, and 1,600, respectively. The drift in XCO2 over 1-hr of flight time was found to be below 0.1 ppm. These analyses demonstrate that the measurement stability, precision, and accuracy are all well below the thresholds needed to study synoptic-scale variations in atmospheric XCO2.
AB - We present an evaluation of airborne intensity-modulated continuous-wave (IM-CW) lidar measurements of atmospheric column CO2 mole fractions during the Atmospheric Carbon and Transport–America (ACT-America) project. This lidar system transmits online and offline wavelengths simultaneously on the 1.57111-μm CO2 absorption line, with each modulated wavelength using orthogonal swept frequency waveforms. After the spectral characteristics of this system were calibrated through short-path measurements, we used the HITRAN spectroscopic database to calculate the average-column CO2 mole fraction (XCO2) from the lidar-measured optical depths. Using in situ measurements of meteorological parameters and CO2 concentrations for calibration data, we demonstrate that our lidar CO2 measurements were consistent from season to season and had an absolute calibration error (standard deviation) of 0.80 ppm when compared to XCO2 values calculated from in situ measurements. By using a 10-s or longer moving average, a precision of 1 ppm or better was obtained. The estimated CO2 measurement precision for 0.1-, 1-, 10-, and 60-s averages was determined to be 3.4, 1.2, 0.43, and 0.26 ppm, respectively. These correspond to measurement signal-to-noise ratios of 120, 330, 950, and 1,600, respectively. The drift in XCO2 over 1-hr of flight time was found to be below 0.1 ppm. These analyses demonstrate that the measurement stability, precision, and accuracy are all well below the thresholds needed to study synoptic-scale variations in atmospheric XCO2.
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U2 - 10.1029/2019EA000847
DO - 10.1029/2019EA000847
M3 - Article
AN - SCOPUS:85097994367
SN - 2333-5084
VL - 7
JO - Earth and Space Science
JF - Earth and Space Science
IS - 12
M1 - e2019EA000847
ER -