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 high-resolution 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.
Highlights
The anthropogenic emissions of greenhouse gases could potentially change the global average temperature, leading to global warming
The latest assessment report of the Intergovernmental Panel on Climate Change (IPCC-AR4) states that climate models are capable of reproducing the temperature trends observed in recent decades if they are forced with increasing concentrations of anthropogenic greenhouse gas (IPCC, 2007)
To demonstrate the differences between the usage of low- and high-resolution CO2 fluxes and between Eulerian and coupled models, we performed a “synthetic” test that examined the transport of CO2 around the city of Moscow, where several large power plants are located, emitting strong plumes of CO2 that are transported to the east of the city by winds
Summary
The anthropogenic emissions of greenhouse gases could potentially change the global average temperature, leading to global warming. In the case of Eulerian models, the evolution of the concentration field is solved numerically using finite difference approximations to the partial differential equation of tracer transport on a fixed grid rather than along the trajectory path (Richtmyer and Morton, 1967) Such models are applied to global-scale simulations of the concentrations of atmospheric constituents and to the inverse modelling of surface fluxes (Gurney et al, 2002, 2004). We extended the approach introduced by Koyama et al (2011) to a high-spatial-resolution case for simulating the concentrations of atmospheric CO2 in the same coupled Eulerian-Lagrangian modelling framework as that used in the earlier study.
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