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 - Funding Information:
The Atmospheric Carbon and Transport (ACT) ‐ America project is a NASA Earth Venture Suborbital 2 project funded by NASA's Earth Science Division. Coauthor Sandip Pal was supported by NASA grant number 80NSSC19K0730 and Texas Tech University start up research grant 14A001‐B5399P‐200. Davis was supported by NASA grant NNX15AG76G to Penn State. C. O'Dell and E. Bell were supported by NASA grant NNX15AI97G to Colorado State University. J.F. Campbell, B. Lin, and M.D. Obland were funded by NASA Science Mission Directorate funding awarded in response to the Earth Venture Suborbital‐2 Announcement of Opportunity NNH13ZDA001N‐EVS2. T. Fan and S. Kooi were covered under NASA contract NNL16AA05C. J. Dobler and W. Erxleben's work was supported by NASA contract NNL15AQ00B.
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
VL - 7
JO - Earth and Space Science
JF - Earth and Space Science
SN - 2333-5084
IS - 12
M1 - e2019EA000847
ER -