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

Abstract

[1] 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. Copyright 2009 by the American Geophysical Union.