Abstract
Abstract. Elevation strongly affects quantity and distribution patterns of precipitation and snow. Positive elevation gradients were identified by many studies, usually based on data from sparse precipitation stations or snow depth measurements. We present a systematic evaluation of the elevation–snow depth relationship. We analyse areal snow depth data obtained by remote sensing for seven mountain sites near to the time of the maximum seasonal snow accumulation. Snow depths were averaged to 100 m elevation bands and then related to their respective elevation level. The assessment was performed at three scales: (i) the complete data sets (10 km scale), (ii) sub-catchments (km scale) and (iii) slope transects (100 m scale). We show that most elevation–snow depth curves at all scales are characterised through a single shape. Mean snow depths increase with elevation up to a certain level where they have a distinct peak followed by a decrease at the highest elevations. We explain this typical shape with a generally positive elevation gradient of snow fall that is modified by the interaction of snow cover and topography. These processes are preferential deposition of precipitation and redistribution of snow by wind, sloughing and avalanching. Furthermore, we show that the elevation level of the peak of mean snow depth correlates with the dominant elevation level of rocks (if present).
Highlights
Complex orography is the main driving factor for the spatial heterogeneity of precipitation
We have shown that the clear majority of subareas are characterised by positive elevation gradients of snow depth with distinct peaks at a certain level
We present a detailed assessment of the relationship of snow depth and elevation
Summary
Complex orography is the main driving factor for the spatial heterogeneity of precipitation. When moist air masses are blocked by mountains, they are forced to ascend the mountain slopes. Declining air temperatures result in a cooling and a decrease of the saturation pressure of the lifted air parcels. Once the saturation level is reached moisture condensation leads to cloud formation and to the onset of precipitation. These processes are enhanced by further lifting which results in an increase of precipitation with elevation up to a certain maximum, which is reached when moisture becomes too depleted from the air mass. The interaction of clouds and precipitation particles with the local wind can strongly modify the precipitation patterns at the ground (Mott et al, 2014; Roe, 2005; Roe and Baker, 2006)
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