Abstract
Abstract. We designed a method to simulate atmospheric
CO2 concentrations at several continuous observation sites
around the globe using surface fluxes at a very high spatial
resolution. The simulations presented in this study were performed
using the Global Eulerian-Lagrangian Coupled Atmospheric
model (GELCA), comprising a Lagrangian particle
dispersion model coupled to a global atmospheric tracer
transport model with prescribed global surface CO2 flux
maps at a 1×1 km resolution. The surface fluxes used in
the simulations were prepared by assembling the individual
components of terrestrial, oceanic and fossil fuel CO2
fluxes. This experimental setup (i.e. a transport model running
at a medium resolution, coupled to a high-resolution Lagrangian
particle dispersion model together with global surface
fluxes at a very high resolution), which was designed to
represent high-frequency variations in atmospheric CO2 concentration,
has not been reported at a global scale previously.
Two sensitivity experiments were performed: (a) using the
global transport model without coupling to the Lagrangian
dispersion model, and (b) using the coupled model with a
reduced resolution of surface fluxes, in order to evaluate
the performance of Eulerian-Lagrangian coupling and the
role of high-resolution fluxes in simulating high-frequency
variations in atmospheric CO2 concentrations. A correlation
analysis between observed and simulated atmospheric
CO2 concentrations at selected locations revealed that the
inclusion of both Eulerian-Lagrangian coupling and highresolution
fluxes improves the high-frequency simulations of
the model. The results highlight the potential of a coupled
Eulerian-Lagrangian model in simulating high-frequency atmospheric
CO2 concentrations at many locations worldwide.
The model performs well in representing observations of atmospheric
CO2 concentrations at high spatial and temporal
resolutions, especially for coastal sites and sites located close
to sources of large anthropogenic emissions. While this study
focused on simulations of CO2 concentrations, the model
could be used for other atmospheric compounds with known
estimated emissions.