Hydrology Days 2002 Scale Effects In The Dependence Of Water Balance Fluxes Partitioning On Soil Moisture

Abstract. The issue of scale in land surface water and energy balance processes has been a dominant research theme for decades [Sposito, 1998]. It is an issue that cannot be avoided in either modeling (i.e. simulation) or in monitoring (i.e. estimation) frameworks. In climate and hydrological modeling it arises from the disparate scales of processes resolved in the atmosphere and land surface. In field estimation it arises from the difficulty to compare point-scale measures (not everywhere and uniformly available) to larger size grids in the modelling discretisation. In both cases, the presence of subgrid heterogeneity of parameters and forcings, as well as lateral flows and nonlinearities in the state dependence of fluxes, renders so-called bottom-up modeling framework both necessary and, most likely, impossible. Moreover, this well-known problem of scale mismatch limits the conclusiveness of validations (generally based on point data) and thus the reliability of model estimates. In this study the focus has been on observed relations among scale fluxes and states, and ways of comparing these relations to existing models (most of which have a point-scale legacy). In particular, the attention has been focused on the water balanc