A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

MODELLING FLUXES FROM AMAZONIAN RAIN FOREST USING A LAND-SURFACE SCHEMEP.P. Harris [ppha@ceh.ac.uk], C. Huntingford [chg@ceh.ac.uk], J.H.C. Gash [jhg@ceh.ac.uk][CEH Wallingford, Maclean Building, Wallingford, Oxon., OX10 8BB, UK.]P.M. Cox [peter.cox@metoffice.com][Met Office, London Road, Bracknell, Berks., UK.]Y. Malhi [ymalhi@ed.ac.uk][Institute of Ecology and Resource Management, University of Edinburgh, Edinburgh, UK.]A.D. Nobre [anobre@inpa.gov.br][Instituto Nacional de Pesquisas da Amazonia, Manaus, Amazonas, Brazil.]The land-surface scheme (MOSES) currently used in the Met Office/Hadley Centre GeneralCirculation Model (HadCM3) simulates the fluxes of energy, momentum, heat, moisture andcarbon dioxide between land and atmosphere for a range of surface types. Until now the ability ofMOSES to simulate the fluxes of Amazonian rain forest has not been tested against observations.Using default parameters, MOSES is able to simulate satisfactorily the measurements of long-termevaporation and heat flux from a rain forest site near Manaus, Amazonas. However, the modelleddaytime net carbon exchange for this site is approximately 52% of the observed sink. Observedfluxes of heat, moisture and carbon dioxide are used to calibrate the model through photosynthesis,stomatal conductance and soil parameters. The model is able to make an adequate simulation ofeither the evaporation or net carbon fluxes, but not both simultaneously. It is suggested that thismay indicate a problem with way the model relates transpiration to photosynthesis throughstomatal conductance. The calibrated model is also tested against an independent set of flux datafrom a nearby site.