Spatial Reallocation of Global Gridded Climate Datasets

Global climatological data are often evaluated in grids with perpendicular boundaries in a cylinder projection of the longitude and latitude circles of the earth. Typical datasets contain 10 6 to 10 8 values. Each dataset is organized in a diierent grid, according to the authors's preferences. When calculating the global radiation over the ocean, for example, it is essential that cloud data from at least three diierent sources can be accessed based on one grid. One approach is to interpolate data from several datasets, each with a diierent grid, and combine them into a single dataset with an arbitrary grid. To this end, all data sets are managed with two Grid Files each: the data le containing measurements and the description le, containing the information of the area grid partition. This allows for an eecient implementation of point and range queries using the symmetric composite key (longitude, latitude, time, name of quantity) and for a reduction of storage space by factors between 2 and 10 as compared to the equivalent ASCII format; the actual reduction obtained depends on the spatial spectra of the datasets. The interpolation makes use of the description les to calculate the weights which are proportional to the areas resulting from the intersection of the grids.