Column CO2 Retrievals from ACES Airborne Lidar Measurements during ACT-America: Case Study from Spring 2018 Campaign

During the NASA Atmospheric Carbon and Transport–America (ACT–America) Spring 2018 campaign, the ASCENDS (Active Sensing of CO2 Emissions over Nights, Days, and Seasons) CarbonHawk Experiment Simulator (ACES) was utilized to measure partial-column CO₂ lidar measurements from the flight altitude to surface while aboard the C-130 aircraft. ACES is an intensity-modulated continuous-wave (IM-CW) lidar developed by the NASA Langley Research Center to measure column-averaged CO₂ mixing ratio (XCO₂). ACES measurements made during the Spring 2018 campaign were processed, analyzed, and compared to the CO₂ optical depths and XCO₂ values derived from airborne in situ CO₂ concentration and meteorological profiling measurements using the HITRAN spectroscopic model. This paper describes the processing, validation, and analysis of the ACES CO2 measurements.