Modelling the water and energy balances of Amazonian rainforest and pasture using Anglo-Brazilian Amazonian climate observation study data

A soil-vegetation-atmosphere transfer model, SWAPS, is introduced. The model is based on existing models for two-layer evaporation and energy balance, interception evaporation and unsaturated soil moisture transport. The model includes a physically based parameterisation for the soil surface resistance to evaporation (as well as a bio-physical vegetation surface resistance). SWAPS is tested against long-term soil moisture data and shorter term flux data from three sites from the Anglo-Brazilian Amazonian Climate Observation Study. Two pasture sites with widely different soil hydraulic properties, and a rainforest site have been used. Flux data are available at these sites under both wet and dry conditions. The model appears to perform well in reproducing the longer term soil moisture as well as surface fluxes. The interception loss for the forest site calculated over the long term agrees with other studies for the Amazonian forest. For the pasture sites the interception loss is less than, but similar to, that of the forest.