Remote Sensing of Spring Snowmelt in Siberia

Abstract

Active as well as passive spaceborne sensors can be used to monitor spring snowmelt on regional to continental scale. Change detection methods are used to determine dates related to the thaw period. They comprise initial thaw, primary thaw, start of diurnal thaw/refreeze period, mean date of thaw, end of thaw and start of greening-up of vegetation. Only the latter is determined by use of passive optical sensors and combines measurements of visible and infrared radiation. All other approaches use microwave data. Some instruments such as the scatterometer Seawinds on QuikScat and the radiometer AMSR-E on Aqua make several measurements per day allowing the detection of diurnal thaw and refreeze, which is characteristic of the spring snowmelt period in northern latitudes. A specific, diurnal difference approach developed for QuikScat allows the determination of the length of the final period of diurnal thaw/refreeze. This duration and the spatial dynamics are closely linked to surface hydrology and ecosystem processes.