Airborne measurements of CO<sub>2</sub> column concentrations made with a pulsed IPDA lidar using a multiple-wavelength-locked laser and HgCdTe APD detector
Here we report on measurements made with an improved CO<sub>2</sub> Sounder lidar during the ASCENDS 2014 and 2016 airborne campaigns. The changes made to the 2011 version of the lidar included incorporating a rapidly wavelength-tunable, step-locked seed laser in the transmitter, using...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-04-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/11/2001/2018/amt-11-2001-2018.pdf |
| Summary: | Here we report on measurements made with an improved CO<sub>2</sub> Sounder
lidar during the ASCENDS 2014 and 2016 airborne campaigns. The changes made
to the 2011 version of the lidar included incorporating a rapidly wavelength-tunable, step-locked seed laser in the transmitter, using a much more
sensitive HgCdTe APD detector and using an analog digitizer with faster
readout time in the receiver. We also improved the lidar's calibration
approach and the XCO<sub>2</sub> retrieval algorithm. The 2014 and 2016 flights
were made over several types of topographic surfaces from 3 to 12 km
aircraft altitudes in the continental US. The results are compared to the
XCO<sub>2</sub> values computed from an airborne in situ sensor during
spiral-down maneuvers. The 2014 results show significantly better performance
and include measurement of horizontal gradients in XCO<sub>2</sub> made over the
Midwestern US that agree with chemistry transport models. The results from the
2016 airborne lidar retrievals show precisions of ∼ 0.7 parts per
million (ppm) with 1 s averaging over desert surfaces, which is an improvement of about 8 times compared to similar measurements made in 2011.
Measurements in 2016 were also made over fresh snow surfaces that have lower
surface reflectance at the laser wavelengths. The results from both campaigns
showed that the mean values of XCO<sub>2</sub> retrieved from the lidar consistently
agreed with those based on the in situ sensor to within 1 ppm. The
improved precision and accuracy demonstrated in the 2014 and 2016 flights
should benefit future airborne science campaigns and advance the
technique's readiness for a space-based instrument. |
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| ISSN: | 1867-1381 1867-8548 |