CHARM-F-a new airborne integrated-path differential-absorption lidar for carbon dioxide and methane observations: measurement performance and quantification of strong point source emissions

Abstract

The integrated-path differential-absorption lidar CHARM-F (CO₂ and CH₄ Remote Monitoring-Flugzeug) was developed for the simultaneous measurement of the greenhouse gases CO₂ and CH₄ onboard the German research aircraft HALO (High Altitude and Long Range Research Aircraft). The purpose is to derive the weighted, column-averaged dry-air mixing ratios of the two gases with high precision and accuracy between aircraft and ground or cloud tops. This paper presents the first measurements, performed in the spring of 2015, and shows performance analyses as well as the methodology for the quantification of strong point sources applied on example cases. A measurement precision of below 0.5% for 20 km averages was found. However, individual measurements still show deviations of the absolute mixing ratios compared to corresponding data from in situ profiles. The detailed analysis of the methane point source emission rate yields plausible results (26±3 m³/min or 9.2±1.15 kt CH₄ yr^-1), which is in good agreement with reported numbers. In terms of CO₂, a power plant emission could be identified and analyzed.