Science Source

The global distribution and dynamics of surface soil moisture

Finds that, according to 33 years of remote sensing data, productivity of US grasslands is more sensitive to dryness of the atmosphere than precipitation, important information for understanding how ecosystems will respond to climate change
States that global observations of surface soil moisture (SSM) are now available from Earth-orbiting satellites
States that an atmospheric anomaly (such as a thunderstorm) will dissipate rapidly (hours), whereas the resulting soil moisture anomaly will take much longer to dissipate (days–months)
Demonstrates that, speaking broadly at global scales, lower groundwater storage in drier regions is due not only to lower precipitation, but also to greater partitioning of the water cycle by the SSM storage
Finds that in regions where drainage to groundwater storage is largest, the surface soil layer retains a lower fraction of incoming precipitation; presumably, more of the precipitation rapidly drains to deeper groundwater storages
Finds that for drier soils, however, hydraulic conductivity (and therefore drainage to groundwater storages) is reduced, as is saturation excess runoff, resulting in a higher fraction of incoming precipitation being retained in the surface soil layer
Results indicate that while surface soil moisture is only a small component of the global water budget (making up less than 0.001% of the global freshwater budget by volume), it plays a substantial role in partitioning water between storages