EGU21-15117, updated on 21 Jul 2021
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Interpretation of Atmospheric CO2 Measurements in Mexico City

Yang Xu1, Michel Ramonet1, Thomas Lauvaux1, Jinghui Lian1, Francois-Marie Bréon1, Philippe Ciais1, Michel Grutter2, and Agustin Garcia2
Yang Xu et al.
  • 1Laboratoire des Sciences du Climat et de l’environment (LSCE-IPSL, CEA-CNRS-UVSQ), France (
  • 2Centro de Cienciasde la Atmósfera, Universidad Nacional Autónoma de México (CCA, UNAM), Mexico

The French-Mexican project Mexico City’s Regional Carbon Impacts (MERCI-CO2) is building a CO2 observation network in the Metropolitan Zone of the Valley of Mexico (ZMVM). The project investigates the atmospheric signals generated by the city's emissions on total column and surface measurements, aiming at reducing the uncertainties of CO2 emissions in ZMVM and evaluating the effects of policies that had been implemented by the city authorities. 

A nested high-resolution atmospheric transport simulation based on the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) is performed to analyze the observed CO2 mixing ratios during dry and wet seasons over Mexico City and its vicinity. Both anthropogenic emissions (UNAM 1-km fossil fuel emissions) and biogenic fluxes (CASA 5-km simulations) are taken into account. The model configuration, with a horizontal resolution of 1km and using the Single-Layer urban canopy Model (SLUCM), has been evaluated over two weeks in January 2018 using meteorological measurements from 26 stations set by the Air Quality Agency of Mexico City (Secretary of the Environment of Mexico City - SEDEMA). The reconstruction of meteorological conditions in the urban area shows better performances than suburban and mountainous areas. Due to the complex topography, wind speeds in mountain areas are 2-3 m/s over estimated and wind direction simulations in some stations are 90° deflected, especially in southern mountains. 

Two high-precision CO2 analyzers deployed in urban and rural areas of Mexico City are used to evaluate the WRF CO2 1-km simulations. The model reproduced the diurnal cycle of CO2 mixing ratios at the background station but under-estimates the nighttime accumulation at the urban station. Mean absolute errors of CO2 concentrations range from 6.5 ppm (background station) to 27.1 ppm (urban station), mostly driven by the elevated nocturnal enhancements (up to 500 ppm at UNAM station). Based on this analysis, we demonstrate the challenges and potential of mesoscale modeling over complex topography, and the potential use of mid-cost sensors to constrain the urban GHG emissions of Mexico City.

How to cite: Xu, Y., Ramonet, M., Lauvaux, T., Lian, J., Bréon, F.-M., Ciais, P., Grutter, M., and Garcia, A.: Interpretation of Atmospheric CO2 Measurements in Mexico City, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15117,, 2021.


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