Helkowski, J.H., J.A. Foley, and M.T. Coe. Effects of 20th century climatic variability on global patterns of soil moisture and runoff. Submitted to Journal of Climate, Oct 2005

Abstract:

The supply of freshwater is a concern in much of the world, especially as population and development pressures continue to feed an increasing need for fresh water. As a result, understanding the spatial and temporal variations in water availability, and their relationships to climate, is crucial. In this study, we used a global hydrological model, at 0.5 ? x 0.5 ? spatial resolution, to examine short and long-term modes of variability in surface hydrological components (including soil moisture and runoff) for the period 1901-1995, and examined their relationships to precipitation and temperature. More specifically, we examined the interannual variability, El Niño/Southern Oscillation (ENSO) associated variability, and low-frequency variability in surface hydrology parameters. We find that different regions of the world exhibit different spatial patterns in soil moisture and runoff anomalies across these three different modes of variability, suggesting that the impacts of different modes differ from each other. Many regions in the tropics experience the highest degree of interannual variability in soil moisture and runoff while drier regions, in terms of average precipitation, generally experience the highest degree of low-frequency variability in these parameters. We also examined the variability of hydrologic parameters over important agricultural regions; significant variations in water availability affect many agriculturally important regions in Canada, the U.S., Argentina, the
Sahel, central Asia, eastern China, and Australia.