A Database of Aircraft Measurements of Carbon Monoxide (CO) with High Temporal and Spatial Resolution during 2011–2021

Abstract. To understand tropospheric air pollution at regional and global scales, the SPIRIT airborne instrument (SPectromètre Infra-Rouge In situ Toute altitude) was developed and used on aircraft to measure volume mixing ratios of carbon monoxide (CO), an important indicator of air pollution, during the last decade. SPIRIT could provide high-quality CO measurements with 1σ precision of 0.3 ppbv at a time resolution of 1.6 s thanks to the coupling of a quantum cascade laser to a Robert multi-pass cell. It can be operated on different aircraft such as Falcon-20 and ATR-42 from DLR (Germany) and SAFIRE (CNRS-CNES-Météo France). With support from various projects, more than 200 flight hours measurements were conducted over three continents (Europe, Asia, and Africa), including two inter-continental measurements (Europe-Asia and Europe-Africa). Levels of CO and its horizontal and vertical distribution are briefly discussed and compared between different regions/continents. CO generally decreases with altitude except for the measurements in high-latitude regions, indicating the important contribution of long-distance transport to CO levels at high-latitude regions. A 3D trajectory mapped by CO level was plotted for each flight and presented in this study. The database is archived on the AERIS database (https://doi.org/10.25326/440), the French national center for atmospheric observations (Catoire et al., 2023). Besides, it could help to validate model performances and satellite measurements. For instance, the database covers measurements at high-latitude regions (i.e., Kiruna, Sweden, 68° N) where satellite measurements are still challengeable and at low-latitude regions (West Africa and South-East Asia) where in situ data are scarce and satellites need more validation by airborne measurements.