ID:
publications-2653
Type:
Peer reviewed articles
Year:
2017
Authors:
Evan S. Miles, Jakob F. Steiner, Fanny Brun
Title:
Highly variable aerodynamic roughness length ( z 0 ) for a hummocky debris-covered glacier
Venue/Journal:
Journal of Geophysical Research: Atmospheres
DOI:
10.1002/2017JD026510
Research type:
Uncategorized
Water System:
River Basins
Technical Focus:
Abstract:
AbstractThe aerodynamic roughness length (z0) is an essential parameter in surface energy balance studies, but few literature values exist for debrisācovered glaciers. We use microtopographic and aerodynamic methods to assess the spatial variability of z0 for Lirung Glacier, Nepal. We apply structure from motion to produce digital elevation models for three nested domains: five 1Ā m2 plots, a 21,300Ā m2 surface depression, and the lower 550,000Ā m2 of the debrisāmantled tongue. Wind and temperature sensor towers were installed in the vicinity of the plots within the surface depression in October 2014. We calculate z0 according to a variety of transectābased microtopographic parameterizations for each plot, then develop a grid version of the algorithms by aggregating data from all transects. This grid approach is applied to the surface depression digital elevation model to characterize z0 spatial variability. The algorithms reproduce the same variability among transects and plots, but z0 estimates vary by an order of magnitude between algorithms. Across the study depression, results from different algorithms are strongly correlated. Using MonināObukov similarity theory, we derive z0 values from the meteorological data. Using different stability criteria, we derive median values of z0 between 0.03Ā m and 0.05Ā m, but with considerable uncertainty due to the glacier's complex topography. Considering estimates from these algorithms, results suggest that z0 varies across Lirung Glacier between ā¼0.005Ā m (gravels) to ā¼0.5Ā m (boulders). Future efforts should assess the importance of such variable z0 values in a distributed energy balance model.
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676819
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