On the Land Surface, Soil Texture, and Water Budget

The land surface is a crucial component of the climate system. Within the land surface, the hydro-physical processes that occur within the soil layer (related to the soil’s texture) distribute soil moisture and modulate the potential surface fluxes. However, comparison of two widely-used global soil texture datasets reveals that substantial differences exist between them. Seasonal simulations were conducted using two ubiquitous soil texture datasets, USDA’s STATSGO dataset and Beijing Normal University’s Global Soil Dataset for Earth System Science, over the continental United States and Mexico. Water retention within the physical soil matrix and the repercussions of those retentive properties on surface fluxes are explored, as well as the differences emanating from changing the assignments of soil texture between these two datasets. The differences in these model simulations are discussed in terms of regional climate variables (i.e., seasonally-averaged 2-m temperature, and humidity) and the evolution of the boundary layer. Results suggest that energy barriers imparted by soil hydro-physical characteristics can determine whether coupling regimes are water-limited or energy-limited, and therefore, can alter the land surface–atmosphere coupling in a non-trivial way. On extended time scales, the retention properties of the soil system adjust the magnitudes of the storage terms in the terrestrial water budget. This research stresses the need for care in making even seemingly innocuous decisions when modeling weather and climate.