Ensembles of boreal summer coupled land-atmosphere climate model integratio
ns for 1987 and 1988 are conducted with and without interactive soil moistu
re to evaluate the degree of climate drift in the coupled land-atmosphere m
odel system, and to gauge the quality of the specified soil moisture datase
t from the Global Soil Wetness Project (GSWP). Use of specified GSWP soil m
oisture leads to improved simulations of rainfall patterns, and significant
ly reduces root-mean-square errors in near-surface air temperature, indicat
ing that the GSWP product is of useful quality and can also be used to supp
ly initial conditions to fully coupled climate integrations. Integrations u
sing specified soil moisture from the opposite year suggest that the intera
nnual variability in the GSWP dataset is significant and contributes to the
quality of the simulation of precipitation above what would be possible wi
th only a mean annual cycle climatology of soil moisture. In particular, sp
ecification of soil wetness from the wrong year measurably degrades the cor
relation of simulated precipitation and temperature patterns compared to ob
served.