Large scale aspects of the United State hydrologic cycle

Abstract

Climatologically, precipitation, which had a US annual mean of more than 2.1 mm day-1, was largely balanced by evaporation; atmospheric moisture flux convergence was also an important contributor (~0.5 mm day-1), especially during the wintertime, and especially along the west coast. At the surface, seasonal and anomalous surface water variations on the order of 10 cm yr-1 were forced by seasonal variations of about 1 mm day-1 in atmospheric moisture flux convergence (precipitation minus evaporation) and streamflow divergence. 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 flux convergence anomalies and less well related to the residual evaporation anomalies. Streamflow divergence anomalies were also related to the atmospheric moisture flux convergence anomalies, especially at lags of around 15 days. A better lag relationship occurred between streamflow divergence and precipitation anomalies. -from Authors