Intercepcao da precipitacao em povoamentos florestais esparsos. Modelacao do processo e caracteristicas aerodinamicas dos cobertos molhados

The rainfall interception process was studied in two Eucalyptus globulus and Pinus pinaster stands from January/92 to July/94. Continuous measurements of gross rainfall, throughfall and stem flow showed that the interception loss was higher in the pine stand than in the eucalypt stand. Interception loss was also simulated by the Rutter model and Gash's original analytical model, but both models overestimated the interception loss from these sparse forests by more than 29%. A reformulated version of the Rutter model greatly improved the accuracy of the simulation for both forests. A new method for the evaluation of the zero plane displacement height was derived using air temperature fluctuation measurements made at two heights. The analysis of the performance of a Gill Instruments sonic anemometer during rainfall showed that the measurements were reliable during these wet periods and that the atmospheric turbulence over the two studied forest canopies was not modified by rainfall. Measurements of evaporation during saturated canopy conditions showed that currently the best solution for modelling wet canopy evaporation from sparse forests is a combination of using an aerodynamic conductance for momentum flux and allowing for incomplete canopy cover, i.e., reducing the evaporation in proportion to the canopy coverAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1249-074 Lisboa, Portugal / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga