Analysis of temporal and spatial variability of atmospheric CO2 concentration within Paris from the GreenLITE tm laser imaging experiment

• Published in: Atmospheric chemistry and physics Vol. 19; no. 22; pp. 13809 - 13825
• Main Authors: Lian, Jinghui, Breon, Francois-Marie, Broquet, Grégoire, Zaccheo, T. Scott, Dobler, Jeremy, Ramonet, Michel, Staufer, Johannes, Santaren, Diego, Xueref-Remy, Irène, Ciais, Philippe
• Format: Journal Article
• Language: English
• Published: European Geosciences Union 2019
• Subjects: Ocean, Atmosphere; Sciences of the Universe
• ISSN: 1680-7316; 1680-7324
• DOI: 10.5194/acp-19-13809-2019

In 2015, the Greenhouse gas Laser Imaging To-mography Experiment (GreenLITE ™) measurement system was deployed for a long-duration experiment in the center of Paris, France. The system measures near-surface atmospheric CO 2 concentrations integrated along 30 horizontal chords ranging in length from 2.3 to 5.2 km and covering an area of 25 km 2 over the complex urban environment. In this study, we use this observing system together with six conventional in situ point measurements and the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and two urban canopy schemes (Urban Canopy Model-UCM; Building Effect Pa-rameterization-BEP) at a horizontal resolution of 1 km to analyze the temporal and spatial variations in CO 2 concentrations within the city of Paris and its vicinity for the 1-year period spanning December 2015 to November 2016. Such an analysis aims at supporting the development of CO 2 atmospheric inversion systems at the city scale. Results show that both urban canopy schemes in the WRF-Chem model are capable of reproducing the seasonal cycle and most of the synoptic variations in the atmospheric CO 2 point measurements over the suburban areas as well as the general corresponding spatial differences in CO 2 concentration that span the urban area. However, within the city, there are larger discrepancies between the observations and the model results with very distinct features during winter and summer. During winter, the GreenLITE ™ measurements clearly demonstrate that one urban canopy scheme (BEP) provides a much better description of temporal variations and horizontal differences in CO 2 concentrations than the other (UCM) does. During summer, much larger CO 2 horizontal differences are indicated by the GreenLITE ™ system than both the in situ measurements and the model results, with systematic east-west variations.