Land surface evaporation and surface conductance from MODIS and flux towers

Routine monitoring of land surface evaporation is of relevance to natural resource managers who require regular, spatially-resolved diagnoses of moisture availability over large areas (regional to continental scale) to manage water resources; assess landscape condition and assess risks such as bushfires, dust storms and flooding. Moreover, the fundamental influence that evaporation has on landscape climates, hydrology and productivity means that there will always be a demand for evaporation measurement and modelling tools of varying levels of complexity, accuracy and spatial resolution.

To address to these needs, we have developed a simple evaporation model that predicts land surface evaporation and surface conductance using MODIS remote sensing. Unlike other models that use remotely-sensed surface temperature, this model uses vegetation indices (NDVI, LAI) and its predictions are constrained using MODIS estimates of GPP. The paper will present: (1) the model and its performance using evaporation measurements from contrasting ecosystems in Australia, a cool temperate evergreen Eucalyptus forest and a wet-dry tropical savanna; (2) the improvements that this approach offers over models that use land surface temperature; and (3) how such a model could be implemented for routine monitoring of evaporation, surface moisture availability and dryness indices.