An Airborne 2-μm Double-Pulsed Direct-Detection Lidar Instrument for Atmospheric CO2 Column Measurements

This study reports airborne measurements of atmospheric CO 2 column density using a 2- μ m double-pulsed integrated path differential absorption (IPDA) lidar. This new 2- μ m IPDA lidar offers an alternative approach to measure CO 2 column density with unique features. The online frequencies of this lidar can be tuned to 1–6 GHz from the CO 2 R30 absorption line peak. It provides high measurement sensitivity to the lower-tropospheric CO 2 near the ground surface. This instrument was flown in the spring of 2014 in a NASA B200 aircraft. The results of these test flights clearly demonstrate the measurement capabilities of this lidar instrument. The CO 2 column dry mixing ratio is compared to an in situ CO 2 measurement by a collocated NOAA flight. The IPDA lidar measurement is determined to be in good agreement with a 0.36% difference, which corresponds to 1.48 ppm. It is the average difference between the IPDA lidar measurements and the NOAA air samples in the flight altitudes from 3 to 6.1 km.