Representation of Space-Time Variability of Soil Moisture

V. Isham1, D.R. Cox2, I. Rodriguez-Iturbe3, A. Porporato4, S. Manfreda3,5


1) Department of Statistical Science, University College London, Gower Street, London WC1E 6BT, UK.

2) Nuffield College, University of Oxford, Oxford OX1 1NF, UK.

3) Department of Civil and Environmental Engineering, Princeton University, Princeton, NJ 08540, USA.

4) Department of Civil and Environmental Engineering, Duke University, Durham, NC 27708, USA.

5) Dipartimento di Ingegneria e Fisica dell'Ambiente (DIFA), University ofBasilicata, Potenza 85100, Italy.

                        

Abstract
A simplified spatial-temporal soil moisture model driven by stochastic spatial rainfall forcing is proposed. The model is mathematically tractable, and allows the spatial and temporal structure of soil moisture fields, induced by the spatial-temporal variability of rainfall and the spatial variability of vegetation, to be explored analytically. The influence of the main model parameters, reflecting the spatial scale of rain cells, the soil storage capacity, the rainfall interception and the soil water loss rate (representing evaporation and deep infiltration) is investigated. The variabilities of the spatially averaged soil moisture process, and that averaged in both space and time, are derived. The present analysis focusses on spatially uniform vegetation conditions; a follow-up paper will incorporate stochastically heterogeneous vegetation.