A possible mechanism for soil moisture bimodality in humid-land environments

The origin and causes for the existence of two distinct steady-state modes of soil moisture probability distribution (pdf) have been attributed to several processes, such as land-atmosphere feedbacks or shifts in climatic conditions within seasons. Here we argue that the interaction between saturated and unsaturated zones in soils with shallow water tables might represent a possible mechanism leading to such bimodality. This conclusion is achieved by analyzing soil water content measurements in vegetated soil columns artificially constructed in a laboratory. We used these observations to develop a stochastic model for the daily soil water balance, which shows how the interplay between the water table and the unsaturated zone is able to induce soil moisture bimodality.Citation: Daly, E., Y. Zinger, A. Deletic, and T. D. Fletcher (2009), A possible mechanism for soil moisture bimodality in humid-land environments, Geophys. Res. Lett., 36, L07402, doi: 10.1029/2008GL036933.