Importance of temporal variability for hydrological predictions based on the maximum entropy production principle

This work builds on earlier work by Kleidon and Schymanski (2008) who explored the use of the maximum entropy production (MEP) principle for modeling hydrological systems. They illustrated that MEP can be used to determine the partitioning of soil water into runoff and evaporation - which determines hydroclimatic conditions around the Globe - by optimizing effective soil and canopy conductances in a way to maximize entropy production by these fluxes. In the present study, we show analytically that under their assumption of constant rainfall, the proposed principle always yields an optimum where the two conductances are equal, irrespective of rainfall rate, evaporative demand, or gravitational potential. Subsequently, we show that under periodic forcing or periodic variations in one resistance (e.g., vegetation seasonality), the optimal conductance does depend on climatic drivers such as the length of dry spells or the time of closure of stomata. Key Points Maximizing entropy production can be used to constrain conductances Assuming constant forcing results in climate independent optimized conductances Dynamics in forcing do result in climate dependent optimal conductance