Toward High-Resolution Global Atmospheric Inverse Modeling Using Graphics Accelerators

The ability of global transport models to go up in resolution becomes discriminating for greenhouse gas atmospheric inversions. This paper describes the porting on Graphics Processing Units of the global transport model currently used in the European operational Copernicus Atmosphere Monitoring Service (CAMS) for CO2 and N2O inversions. It represents an important milestone to achieve sub-degree resolution. The code includes not only the direct model but also its tangent-linear and its adjoint versions which are needed in variational inversions. Tests were carried out for CO2 at a resolution of 2.50 degrees in longitude, 1.27 degrees in latitude and 79 layers in the vertical, corresponding to 1,626,768 3D cells, 4.5 times more than the current standard resolution of the model used in the CAMS reanalyzes. A month's worth of computation of the tangent-linear and of the adjoint versions now takes 2.5 min, including 50 s for reading meteorological data.