Abstract
Abstract. The quality of the representation of greenhouse gas (GHG) transport in atmospheric general circulation models (GCMs) drives the potential of inverse systems to retrieve GHG surface fluxes to a large extent. In this work, the transport of CO2 is evaluated in the latest version of the Laboratoire de Météorologie Dynamique (LMDz) GCM, developed for the Climate Model Intercomparison Project 6 (CMIP6) relative to the LMDz version developed for CMIP5. Several key changes have been implemented between the two versions, which include a more elaborate radiative scheme, new subgrid-scale parameterizations of convective and boundary layer processes and a refined vertical resolution. We performed a set of simulations of LMDz with different physical parameterizations, two different horizontal resolutions and different land surface schemes, in order to test the impact of those different configurations on the overall transport simulation. By modulating the intensity of vertical mixing, the physical parameterizations control the interhemispheric gradient and the amplitude of the seasonal cycle in the Northern Hemisphere, as emphasized by the comparison with observations at surface sites. However, the effect of the new parameterizations depends on the region considered, with a strong impact over South America (Brazil, Amazonian forest) but a smaller impact over Europe, East Asia and North America. A finer horizontal resolution reduces the representation errors at observation sites near emission hotspots or along the coastlines. In comparison, the sensitivities to the land surface model and to the increased vertical resolution are marginal.
Highlights
The accumulation of carbon dioxide (CO2) in the atmosphere due to anthropogenic activity is one of the primary drivers of climate change (Ciais et al, 2014a)
In the Supplement, we show the robustness of our conclusions with respect to a change of the CO2 surface fluxes from CAMS to CarbonTracker
Another part of the diurnal variability is induced by boundary layer processes: during nighttime, CO2 accumulates near the surface within the shallower stable boundary layer, whereas during daytime, the low CO2 concentration caused by the photosynthesis uptake is distributed over a deeper convective planetary boundary layer (PBL)
Summary
The accumulation of carbon dioxide (CO2) in the atmosphere due to anthropogenic activity is one of the primary drivers of climate change (Ciais et al, 2014a). Since Locatelli et al (2015a), new versions of the full LMDz GCM have been developed, e.g. for the ongoing CMIP6 The latter benefits from a resolution increased to 79 vertical layers and more elaborate subgrid-scale parameterizations in terms of convection and boundary layer processes. This version has been primarily developed for climate modelling and has not been tested yet for the transport of tracers such as CO2.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
