A comprehensive global root database is used to derive vertical root distribution and rooting depth for various vegetation categories in one of the most widely-used land models; i.e., the Biosphere-Atmosphere Transfer Scheme (BATS). Using a variety of observational datasets, observed root distribution is found to significantly improves the offline simulation of surface water and energy balance. Global climate modeling further demonstrates that observed root distribution primarily affects latent heat flux and soil wetness over tropical and midlatitude land, respectively. ¿ 1998 American Geophysical Union