Intercomparison of Airborne Carbon Monoxide Measurements During the 2022 Asian Summer Monsoon Chemistry and CLimate Impact Project (ACCLIP)

With redundant sensors on two co-located research aircraft, the 2022 ACCLIP field study based in Osan, South Korea, presented a valuable carbon monoxide measurement intercomparison opportunity. Adequate coincident measurements were obtained for 4 instruments on the NASA WB-57 aircraft and for 3 on the NSF NCAR G-V platform.

The NASA WB-57 aircraft payload included three continuous and one integrated canister sampling in situ sensors: Carbon Oxide Laser Detector 2 (COLD2), Carbon mOnoxide Measurement from Ames (COMA), Airborne Carbonyl Sulfide (ACOS), and Whole Air Sampler (WAS). ACCLIP was the first high altitude deployment for two of these sensors (COMA, ACOS). COLD2 is a laser spectrometer, based on a mid-infrared quantum cascade laser and a multipass cell. The detection technique is direct absorption, and target gases are carbon monoxide (CO) and nitrous oxide (N₂O). NASA’s Carbon mOnoxide Measurement from Ames (COMA) is an Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) instrument (ABB Ltd.) modified for high-altitude airborne in-situ measurements of carbon monoxide (CO) and nitrous oxide (N₂O). NOAA’s ACOS is a laser spectrometer which utilizes a ICOS multipass sample cell and a mid-IR scanning quantum cascade laser, with primary detection species of carbon monoxide (CO) and Carbonyl Sulfide (OCS). WAS is a system of stainless steel canisters collecting time-integrated whole air samples for offline laboratory compositional analysis. Carbon monoxide is quantified post-project by the NCAR Picarro cavity ringdown spectrometer.

The NSF NCAR Gulfstream V payload included two NCAR continuous and one integrated canister sampling in situ sensors: a QCL mid-infrared absorbance spectrometer (Aerodyne Research, Inc.) quantifying carbon monoxide (CO)and nitrous oxide (N₂O), and a cavity ringdown spectrometer (Picarro) for quantification of carbon monoxide (CO), carbon dioxide (CO₂) and methane (CH₄). A WAS system was also part of the G-V payload.

Presented here are results comparing instrument performance on both aircraft. In addition to intra-platform comparisons, higher altitude portions of several ascents and descents, as well as coordinated high altitude sampling transects provided enough measurement coincidence to also allow meaningful comparison of instruments across the two platforms.