Albedo-mediated interactive effects of land- and snow cover changes on the radiative forcing in Northern Italy

Abstract

<p>The Alps are experiencing large climatic and socio-economic changes. Climate change is leading to an above-average increase in temperatures and subsequent changes in the timing and duration of snow cover. In parallel, socio-economic changes are affecting land use in the Alpine region. Both, snow cover duration/timing and land use changes directly affect the surface albedo of this landscape and therefore the energy balance of this region. Globally, changes in surface albedo due to land use changes and changes in snow/ice cover affect surface albedo, and thus radiative forcing, in opposite directions.<br>In this study, we investigated the impact of four different future land use scenarios, 12 future snow cover scenarios on the surface albedo in the alpine region of South Tyrol (Italy) in the year 2100 compared to conditions in 2010. Both, the individual effects of changes in land use and future snow cover patterns were investigated, as well as the interactive effects of these two processes.<br>The hypothetical changes in albedo until 2100 associated with changes in land and/or snow cover were assessed by establishing a surface albedo model based on remotely sensed albedo (MODIS MCD43A1), snow cover data (MODIS MOD10A1), land cover data, as well as geographical information (ASTER ASTGTM).  Potential future land covers were developed on the basis of likely socio-economic pathways and their spatial distribution was mapped. Snow cover scenarios for 2100 are based on EURO CORDEX RCP 2.6 and 8.5 climate scenarios.<br>Snow cover was by far the most important predictor for albedo, followed by the occurrence of needle leaf forests using a regression tree algorithm. This algorithm exhibited excellent skill in modelling current albedo conditions based on the above-mentioned predictors.<br>Likely future snow cover conditions lead to a decrease in average albedo, the magnitude of which depended on the chosen RCP and combination of global/regional climate model. Likely future land cover scenarios caused changes in spatially averaged albedo of the study domain in the same order of magnitude like the RCP 2.6 snow cover scenarios. Simulations with factorial combinations of land cover and snow cover scenarios showed the compounding effect of these two processes. </p><p> </p><p> </p>