The dataset (Mielke et al, 2023) consists of daily ASCII-files, each containing the spherical harmonic coefficients (SHCs) for atmosphere, hydrology, and ocean bottom pressure. The files that include the AH+O coefficients are provided in the AOD format of the GFZ with the naming convention TYPE_YYYY-MM-DD_X_01.asc and contain header information (30 lines) and four columns with degree (n) order (m) and Stokes coefficients cnm and snm. Coefficients in each file are split up into different subsets, each corresponding to a subdaily time step (i.e., a daily file with 3-hour temporal resolution is split up into 8 subsets).
The entire dataset is organized following the folder structure /TYPE/NEST/coeff_aodFormat_XXX/. We provide regional refined (nested), coarse grained (nested, but with a lower resolution version of the regional model), or global model solutions of SHCs for each datatype. Some datasets are available in different spectral resolutions, with d/o up to 179, 180, or 360. In this release all AH+O coefficients have a temporal resolution of 3 hours, except the non-regional refined atmospheric solution, which is given 6-hourly. Currently, the whole data set is provided for June 2007 and some components for the whole year 2007. Additional months and years will be added with newer versions of the dataset or can be provided by the authors on request.
For the atmospheric and hydrological background model, regional models with high spatial and temporal resolution are nested into global models: Therefore, global and regional models must be resampled and interpolated on the same regular grid with equivalent time epochs. For the nesting, the global model is interpolated on the same grid resolution as the regional model. Grid points of the global model are than replaced with the data of the regional model of the CORDEX-EU region. A Gaussian filter is applied in a transition zone with a width of 7.5° to reduce an edge effect (Gibbs effect) between the two combined models.