Hydrometeorology is a branch of meteorology and hydrology that studies the transfer of water and energy between the land surface and the lower atmosphere, producing an ever more advance knowledge about the water cycle. Hydrometeorology deals with problems involving the hydrologic cycle, the water budget, and the rainfall statistics of storms. Hydrometeorology basically represents an effort to impart a ‘combined approach perspective’ focusing at the interface between hydrology and meteorology. Hydrometeorologic studies address the queries concerning land use, the long-term effects of climate change on water resources, and regional precipitation. Considerable emphasis is placed on determining, theoretically or empirically, the relationships between meteorological variables and the maximum precipitation reaching the ground. These analyses often serve as the bases for the design of flood-control and water-usage structures, primarily dams and reservoirs. Other concerns of hydrometeorologists include the determination of rainfall probabilities, the space and time distribution of rainfall and evaporation, the recurrence interval of major storms, snow melt and runoff, and probable wind tides and waves in reservoirs. The whole field of water quality and supply is of growing importance in hydrometeorology. Hydrometerology deals with the modeling, observing, and forecasting of processes related to water and energy fluxes and storage terms; including interactions with the boundary layer and lower atmosphere, and including processes related to precipitation, radiation, and other meteorological inputs.