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TitleThe influence of DEM resolution on simulated solar radiation-induced glacier melt
AuthorHopkinson, C; Chasmer, L; Munro, S; Demuth, M N
SourceHydrological Processes 24, 2010 p. 775-788,
Alt SeriesEarth Sciences Sector, Contribution Series 20090262
Mediapaper; on-line; digital
File formatpdf
AreaRocky Mountains; Peyto Glacier
Lat/Long WENS-116.7500 -116.5000 51.7500 51.5833
Subjectssurficial geology/geomorphology; glaciers; modelling; digital elevation models; lidar; geographic information system application
ProgramEarth Science for National Scale Characterization of Climate Change Impacts on Canada's Landmass, Climate Change Geoscience
ProgramCanadian Space Agency (GRIP).
AbstractThe influence of DEM resolution to modeled glacier melt during peak melt production was evaluated by performing a clear sky GIS radiation simulation over the Peyto Glacier in the Canadian Rockies. DEMs were generated at eight resolutions ranging from 1m to 1000m grid spacing from airborne lidar data. When applied to the planar area (PA) of the terrain, it was found that total melt increased with DEM resolution (r2 17 = 0.63) by 4% over three orders of magnitude. This systematic scaling-effect was mitigated at the basin scale, however, when the DEM slope variant area (SVA) was used to account for the increased divergence from PA as resolution increases. However, even after the inclusion of SVA in glacier surface melt simulations, localized melt variations with scale were still evident in the ablation and accumulation zone observations. In the ablation zone there was a systematic increase in simulated melt (~4%) as resolution decreased from 1m to 1000m (r2 = 0.89), with the opposite effect in the accumulation zone (r2 = 0.81). DEM resolution also impacted the diurnal melt cycle, such that for the entire glacier there was a tendency for a morning overestimation and afternoon underestimation of melt rate with decreasing resolution. For the accumulation zone there was an increased melt-rate at low resolutions occurring in the afternoon, while in the ablation zone there was a tendency for increasing melt rates with decreasing resolution throughout the day. These localized spatio-temporal variations in simulated melt are largely due to the lowering of ridges and raising of valley floors that occur as resolution decreases. This scale dependence in the representation of terrain morphology directly controls the pattern and relative proportion of direct beam shadowing over actively melting surfaces and thereby has a systematic influence on the grid cell-level hydrological balance. It is recommended that GIS-based glacier melt modeling routines take into account the slope area of grid cells, while noting that the choice of DEM scale can have a discernible and systematic influence on modeled runoff magnitude. It is important to note that while higher grid resolutions mitigate the effect of terrain smoothing on spatio-temporal melt patterns, lower resolutions actually mitigate the systematic error associated with assuming all surface areas are planar.