Abstract. Anthropogenic point sources, such as coal-fired power plants, produce a major share of global CO₂ emissions. International climate agreements demand their independent monitoring. Due to the high amount of point sources and their global spatial distribution, a mobile measurement approach with fast spatial coverage is needed. Active remote sensing measurements by airborne lidar show much promise in this respect. The integrated-path differential-absorption lidar CHARM–F is installed onboard an aircraft, in order to detect weighted vertical columns of CO₂ mixing ratios, below the aircraft along its flight track. During the Carbon Dioxide and Methane mission (CoMet) in spring 2018, airborne greenhouse gas measurements were performed, focusing on the major European sources of anthropogenic CO₂ emissions, i.e. large coal–fired power plants. The flights were designed to transect isolated exhaust plumes. From the resulting enhancement in the CO₂ mixings ratios, emission rates can be derived in terms of the cross–sectional flux method. On average, we find our results roughly corresponding to reported annual emission rates, but observe significant variations between individual overflights ranging up to a factor of 2. We suppose that these variations are mostly driven by turbulence. This hypothesis is supported by a high–resolution large eddy simulation that enables us to give a qualitative assessment of the influence of plume inhomogeneity on the cross–sectional flux method. Our findings suggest avoiding periods of strong turbulence, e.g. midday and afternoon. More favorable measurement conditions prevail during nighttime and morning. Since lidars are intrinsically independent of sunlight, they have a significant advantage in this regard.

中文翻译：

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机载激光雷达确定CO ₂点源的排放率

摘要。人为的点源，例如燃煤电厂，在全球CO ₂排放量中占很大份额。国际气候协定要求对其进行独立监测。由于大量的点源及其全局空间分布，需要一种具有快速空间覆盖的移动测量方法。在这方面，机载激光雷达的主动遥感测量显示出很大的希望。集成路径差吸收激光雷达CHARM–F安装在飞机上，以检测CO _2的垂直垂直柱混合比，位于飞机沿飞行轨迹的下方。在2018年春季的二氧化碳和甲烷任务（CoMet）期间，进行了机载温室气体测量，重点是欧洲人为造成的CO ₂排放的主要来源，即大型燃煤电厂。这些飞行被设计成横切孤立的废气羽流。从产生的CO ₂增强中混合比，排放率可以根据截面通量法得出。平均而言，我们发现我们的结果大致与报告的年排放量相对应，但是观察到单个飞越之间的显着变化范围高达2倍。我们认为这些变化主要是由湍流驱动的。高分辨率大涡流仿真支持这一假设，使我们能够对羽状不均匀性对截面通量方法的影响进行定性评估。我们的发现表明，应避免出现剧烈动荡的时期，例如中午和下午。夜间和早晨会出现更有利的测量条件。由于激光雷达本质上与阳光无关，因此在这方面它们具有明显的优势。