Modification of DAISY SVAT model for potential use of remotely sensed data

The SVAT model DAISY is modified to be able to utilize remote sensing (KS) data in order to improve prediction of evapotranspiration and photosynthesi s: at plot scale. The link between RS data and the DAISY model is the devel opment of the minimum, unstressed, canopy resistance r(c)(min) during the g rowing season. Energy balance processes are simulated by applying resistanc e networks and a two-source model. Modeled data is validated against measur ements performed for a winter wheat plot. Soil water content is measured by time domain reflectometry. Crop dry matter content and leaf area index are modeled adequately. Modeled soil water content, based on a Brooks and Core y [Brooks. R.H., Corey, A.T., 1964. Hydraulic properties of porous media. H ydrology Paper no. 3, Colorado University, Fort Collins, CO. 27 pp.] parame terization. from 0 to 20, 0 to 50 and 0 to 100 cm is calibrated satisfactor ily against measured TDR values. Simulated and observed energy fluxes are g enerally in good agreement when water supply in the root zone is not limiti ng. With decreasing soil moisture content during a longer drought period, m odeled latent heat flux is: lower than observed, which calls for both impro ved parameterizations for environmental controls and for a improved estimat ion of the r(c)(min) parameter. (C) 2001 Elsevier Science B.V. All rights r eserved.