A Simple Method to Determine the Timing of Snow Melt by Remote Sensing with Application to the CO₂ Balances of Northern Mire and Heath Ecosystems

摘要

The timing of the disappearance of the snow cover in spring, or snow melt day (SMD), is a key parameter controlling the carbon dioxide balance between the northern mire and heath ecosystems and the atmosphere. We present a simple method for the determination of the SMD using a satellite-based surface albedo product (SAL). The method is based on the local change of albedo from higher wintertime values towards the lower summertime values. The satellite SMD timing correlates well with the SMD determined from snow depth measurements at Finnish weather stations (r = 0.86, slope 1.05). In 50% of the cases the error was 3.4 days or less and bias less than half a day. This would lead to a moderate uncertainty in the annual CO₂ balance of mire and heath ecosystems, if the published SMD—CO₂ balance relations are valid. However, due to the limited data sets available a systematic validation is left for the future.