Abstract
Abstract. The most widely used method for snow dynamic simulation relies on temperature index approach, that makes snow melt and accumulation processes depend on air temperature related parameters. A recently used approach to calibrate these parameters is to compare model results with snow coverage retrieved from satellite images. In area with complex topography and heterogeneous land cover, snow coverage may be affected by the presence of shaded area or dense forest that make pixels to be falsely classified as uncovered. These circumstances may have, in turn, an influence on calibration of model parameters. In this paper we propose a simple procedure to correct snow coverage retrieved from satellite images. We show that using raw snow coverage to calibrate snow model may lead to parameter values out of the range accepted by literature, so that the timing of snow dynamics measured at two ground stations is not correctly simulated. Moreover, when the snow model is implemented into a continuous distributed hydrological model, we show that calibration against corrected snow coverage reduces the error in the simulation of river flow in an Alpine catchment.
Highlights
The snow dynamic and its spatial variability act as a “large mountain” reservoir due to the shift in time of the water volume determining the flow regime in the rivers network
In this paper we propose a simple procedure to correct snow coverage retrieved from satellite images
We show that using raw snow coverage to calibrate snow model may lead to parameter values out of the range accepted by literature, so that the timing of snow dynamics measured at two ground stations is not correctly simulated
Summary
The snow dynamic and its spatial variability act as a “large mountain” reservoir due to the shift in time of the water volume determining the flow regime in the rivers network. Despite the important role played by the snow and despite the capability reached by scientists and technicians to model its dynamic, one of the main uncertainties lies in the determination of the snow covered areas and of their water equivalent This is due to the well known difficulties of monitoring snow parameters and of detecting the snow coverage on areas of complex topography or densely forested (Bocchiola and Rosso, 2007; Simpson et al, 1998; Baral and Gupta, 1997). The potentiality of images from remote sensing is well assessed by the scientific community (Baumgartner et al, 1994; Metsiimiiki et al, 1998; Parajka and Bloschl, 2008), but the conversion from qualitative data to quantitative ones is still very complex This is due to the spatial and radiometric integration underlined in the pixel value of digital number given for any satellite image. The methodology is validated at basin scale where a good agreement between observed and simulated hydrographs at the river Toce basin outlet (Italy) is observed after model was calibrated against corrected images
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