LARGE-SCALE ASPECTS OF THE UNITED-STATES HYDROLOGIC-CYCLE

A large-scale, gridpoint, atmospheric, hydrologic climatology consisti ng of atmospheric precipitable water, precipitation, atmospheric moist ure flux convergence, and a residual evaporation for the conterminous United States is described. A large-scale, basin, hydrologic climatolo gy of the same atmospheric variables is also described, as well as res idual surface water and streamflow divergence or runoff for various la rge-scale river basins terminating at the United States boundary. Clim atologically, precipitation, which had a U.S. annual mean of more than 2.1 mm day-1, was largely balanced by evaporation; atmospheric moistu re flux convergence was also an important contributor (approximately 0 .5 mm day-1), especially during the wintertime, and especially along t he U.S. west coast. At the surface, seasonal and anomalous surface wat er (including snow) variations on the order of 10 cm yr-1 were forced by seasonal variations of about 1 mm day-1 in atmospheric moisture flu x convergence (precipitation minus evaporation) and streamflow diverge nce. The strongest seasonal variations were found along the West Coast . Unlike the climatological means and seasonal variations, atmospheric precipitation anomalies were best related to atmospheric moisture flu x convergence anomalies and less well related to the residual evaporat ion anomalies. Streamflow divergence anomalies were also related to th e atmospheric moisture flux convergence anomalies, especially at lags of around 15 days. A better lag relationship occurred between streamfl ow divergence and precipitation anomalies.