Detectability of CO 2 emission plumes of cities and power plants withthe Copernicus Anthropogenic CO 2 Monitoring (CO2M) mission

Abstract. High-resolution atmospheric transport simulations were used to investigate the potential for detecting carbon dioxide (CO 2 ) plumes of the city of Berlin and neighboring power stations with the Copernicus Anthropogenic Carbon Dioxide Monitoring (CO2M) mission, which is a proposed constellation of CO 2 satellites with imaging capabilities. The potential for detecting plumes was studied for satellite images of CO 2 alone or in combination with images of nitrogen dioxide (NO 2 ) and carbon monoxide (CO) to investigate the added value of measurements of other gases co-emitted with CO 2 that have better signal-to-noise ratios. The additional NO 2 and CO images were either generated for instruments on the same CO2M satellites (2×2 km 2 resolution) or for the Sentinel-5 instrument (7×7 km 2 ) assumed to fly two hours earlier than CO2M. Realistic CO 2 , CO and NO 2 fields were simulated at 1×1 km 2 horizontal resolution with COSMO-GHG model for the year 2015, and used as input for an orbit simulator to generate synthetic observations of columns of CO 2 , CO and NO 2 for constellations of up to six satellites. A new plume detection algorithm was applied to detect coherent structures in the images of CO 2 , NO 2 or CO against instrument noise and variability in background levels. Although six satellites with an assumed swath of 250 km were sufficient to overpass Berlin on a daily basis, only about 50 out of 365 plumes per year could be observed in conditions suitable for emission estimation due to frequent cloud cover. With the CO 2 instrument only 6 and 16 of these 50 plumes could be detected assuming a high (σ VEG50 = 1.0 ppm) and low noise (σ VEG50 = 0.5 ppm) scenario, respectively, because the CO 2 signals were often too weak. A CO instrument with specifications similar to the Sentinel-5 mission performed worse than the CO 2 instrument, while the number of detectable plumes could be significantly increased to about 35 plumes with an NO 2 instrument. Using NO 2 observations from the Sentinel-5 platform instead resulted in a significant spatial mismatch between NO 2 and CO 2 plumes due to the two hour time difference between Sentinel-5 and CO2M. The plumes of the coal-fired power plant Janschwalde were easier to detect with the CO 2 instrument (about 40–45 plumes per year), but again, an NO 2 instrument performed significantly better (about 70 plumes). Auxiliary measurements of NO 2 were thus found to greatly enhance the capability of detecting the location of CO 2 plumes, which will be invaluable for the quantification of CO 2 emissions from large point sources.