The operative remote sensing of snow covered area in a service of hydrological modelling in Finland

摘要

A method for monitoring Snow Covered Area (SCA) using optical remote sensing data is presented. The monitoring results during the snowmelt season 2003 were assimilated with the Finnish national hydrological forecasting system in order to obtain best possible forecasts. The remote sensing method is based on a semi-empirical reflectance model, where reflectance from target area is expressed as a function of forest transmissivity, SCA and three major reflectance contributors (snow, snow-free ground, and forest canopy). The assimilation procedure requires information on the accuracy for each SCA-estimate. For reflectance model, these are obtained by applying the standard law of error propagation using empirically gained standard deviations for all parameters of the model. The success of the joint use of remote sensing and hydrological modeling is presented for a drainage basin located in southern Finland. The results indicate that spatial information of SCA can drastically improve the forecasting accuracy particularly at the end of the melting season.