Relative contributions of land and ocean processes to precipitation variability 
Randal D. Koster 
Hydrological Sciences Branch, Laboratory for Hydrospheric Processes, NASA Fliglrt, 
Center, Greenbelt. Mlaryland Goddard Space 
Max J. Suarez, 
Climatc and Radiation Brauch, Center, Greenbelt, Maryland Laboratory for 
Atmosphreres, NASA Goddard Space Flight, 

Abstract.
 A series of general circulation model simulations are used to quantify the relative 
contributions of land surface and ocean variability to variability in precipitation. 
The simulations show that land surface processes contribute significantly to the 
variance of annual precipitation over continents. In contrast, ocean processes acting 
alone have a much smaller effect, particularly in midlatitudes. The prceipitation 
variability reflects local evaporation variability and associated hydrological 
persistence, and it, responds most strongly to the land surface during summer, when 
moist convection dominates.