cover leads to large uncertain- ties in permafrost monitoring (Langer et al., 2013). Numer- ous studies suggest that differing timing and duration of snow coverage have strong influences on ground surface [...] finally, thawing per- mafrost has an impact on industrial sites in the high arctic. 90 Several studies have already reported about changes in the thermal state of permafrost with increasing temperatures [...] for clear-sky 25 conditions (Wan, 1999), significantly reduced accuracies are shown by numerous studies from Arctic regions for individ- ual measurements as well as for hereof derived time-series (Hachem