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The current version of the NASA Surface meteorology and Solar Energy Datasets, SSE (Rel. 6.0), derived its monthly mean direct normal irradiances (DNIs) directly from the NASA GEWEX SRB (Rel. 3.0) monthly mean global horizontal irradiances (GHIs) and the employed methodology relates the DNI to GHI in terms of monthly mean clearness index, latitudinal range, and solar geometry on the monthly average day. The coefficients of the relations were empirically derived from regression analysis of the BSRN data over the period from 1992 to 2005. While the derived monthly mean SSE (Rel. 6.0) DNIs show reasonable agreement with their BSRN counterparts, improvements in the quality of the dataset and DNIs on shorter time scales were realized through the application of the D1RINDEX model to the 3-hourly GHIs of the NASA GEWEX SRB (Rel. 3.0) data to produce 3- hourly DNIs. The DIRINDEX model is a combination of the DIR1NT model and a simplified version of the SOLIS clear-sky model, and the model was modified to accommodate a wider range of input parameters than originally designed. Additional input parameters include solar geometric, geographic and atmospheric parameters. The results are 3-hourly, daily, and monthly mean DNIs spanning 2000 to 2005 on a quasi-equalarea grid system of 44016 grid cells covering the entire globe. The data are then re-gridded onto a l°x l° grid system for the convenience of users. The resulting monthly mean DNIs show better agreement with the BSRN data than the SSE (Rel. 6.0) DNIs do. To further improve the results, we assimilated the ground-based BSRN data into the DNIs using the inverse-distance interpolation in the latitude-longitude-cosine of solar zenith angle phase space. [ABSTRACT FROM AUTHOR]