Abstract. To date, lumped rainfall-runoff models rely on rough estimates of catchment-averaged potential evapotranspiration (ETp) rates as meteorological forcing. A model parameter converts this ETp input into actual evapotranspiration (ETact) estimates. This paper examines the potential use of scintillometer-based ETact rates for rainfall-runoff modeling. It has been found that the reservoir-structure of the rainfall-runoff model functions as a low-pass filter for the ETp input. If the long-term volume of the ETp used in the model simulations is consistent with the data set used for calibration, a good match of the seasonal pattern, using temporally constant ETp data, is sufficient to obtain adequate discharge simulations. However, these results are then obtained with strongly erroneous evapotranspiration estimates. A better match of the diurnal cycle does not lead to better model results. Replacing the ETp inputs by scintillometer-based ETact estimates does not lead to better model predictions. Small underestimations of ETact under stable conditions, which occur at night and during the Winter, and which accumulate to significant amounts, are the cause of this problem. Consistent with other studies, the scintillometer-based ETact estimates can be considered reliable and realistic under unstable conditions. These values can thus be used as forcing for rainfall-runoff models.
Noise Reduction from L-Band ALOSPALSAR Data Set Using Spatial Domain Gaussian Low-Pass Filter