Micrometeorological processes driving snow ablation in an Alpine catchment
Micrometeorological processes driving snow ablation in an Alpine catchment
Mountain snow covers typically become patchy over the course of a melting season. The snow pattern during melt is mainly governed by the end of winter snow depth distribution and the local energy balance. The objective of this study is to investigate micrometeorological processes driving snow ablation in an Alpine catchment. For this purpose we combine a meteorological model (ARPS) with a fully distributed energy balance model (Alpine3D). Turbulent fluxes above melting snow are further investigated by using data from eddy-correlation systems. We compare modelled snow ablation to measured ablation rates as obtained from a series of Terrestrial Laser Scanning campaigns covering a complete ablation season. The measured ablation rates indicate that the advection of sensible heat causes locally increased ablation rates at the upwind edges of the snow patches. The effect, however, appears to be active over rather short distances except for very strong wind conditions. Neglecting this effect, the model is able to capture the mean ablation rates for early ablation periods but strongly overestimates snow ablation once the fraction of snow coverage is below a critical value. While radiation dominates snow ablation early in the season, the turbulent flux contribution becomes important late in the season. Simulation results indicate that the air temperatures appear to overestimate the local air temperature above snow patches once the snow coverage is below a critical value. Measured turbulent fluxes support these findings by suggesting a stable internal boundary layer close to the snow surface causing a strong decrease of the sensible heat flux towards the snow cover. Thus, the existence of a stable internal boundary layer above a patchy snow cover exerts a dominant control on the timing and magnitude of snow ablation for patchy snow covers.
2159-2196
Mott, R.
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Egli, L.
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Grunewald, T.
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Dawes, N.
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Manes, C.
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Bavay, M.
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Lehning, M.
72ba397f-301c-476f-83b0-d37f7620731e
2011
Mott, R.
269a0451-a600-4d9f-a038-ad0de0a7d003
Egli, L.
09f83dba-7788-406c-8035-8bac97be1bc9
Grunewald, T.
827fb220-7193-40ba-a4fc-acd137479bda
Dawes, N.
32637c22-60d6-4678-a292-56922f5efa33
Manes, C.
7d9d5123-4d1b-4760-beff-d82fe0bd0acf
Bavay, M.
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Lehning, M.
72ba397f-301c-476f-83b0-d37f7620731e
Mott, R., Egli, L., Grunewald, T., Dawes, N., Manes, C., Bavay, M. and Lehning, M.
(2011)
Micrometeorological processes driving snow ablation in an Alpine catchment.
The Cryosphere Discussions, 5, .
(doi:10.5194/tcd-5-2159-2011).
Abstract
Mountain snow covers typically become patchy over the course of a melting season. The snow pattern during melt is mainly governed by the end of winter snow depth distribution and the local energy balance. The objective of this study is to investigate micrometeorological processes driving snow ablation in an Alpine catchment. For this purpose we combine a meteorological model (ARPS) with a fully distributed energy balance model (Alpine3D). Turbulent fluxes above melting snow are further investigated by using data from eddy-correlation systems. We compare modelled snow ablation to measured ablation rates as obtained from a series of Terrestrial Laser Scanning campaigns covering a complete ablation season. The measured ablation rates indicate that the advection of sensible heat causes locally increased ablation rates at the upwind edges of the snow patches. The effect, however, appears to be active over rather short distances except for very strong wind conditions. Neglecting this effect, the model is able to capture the mean ablation rates for early ablation periods but strongly overestimates snow ablation once the fraction of snow coverage is below a critical value. While radiation dominates snow ablation early in the season, the turbulent flux contribution becomes important late in the season. Simulation results indicate that the air temperatures appear to overestimate the local air temperature above snow patches once the snow coverage is below a critical value. Measured turbulent fluxes support these findings by suggesting a stable internal boundary layer close to the snow surface causing a strong decrease of the sensible heat flux towards the snow cover. Thus, the existence of a stable internal boundary layer above a patchy snow cover exerts a dominant control on the timing and magnitude of snow ablation for patchy snow covers.
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Mott_et_al_2011.pdf
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Published date: 2011
Organisations:
Energy & Climate Change Group
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Local EPrints ID: 204131
URI: http://eprints.soton.ac.uk/id/eprint/204131
ISSN: 1994-0440
PURE UUID: 35a544fe-8005-4ceb-be30-819b110503dd
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Date deposited: 24 Nov 2011 11:17
Last modified: 14 Mar 2024 04:30
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Author:
R. Mott
Author:
L. Egli
Author:
T. Grunewald
Author:
N. Dawes
Author:
C. Manes
Author:
M. Bavay
Author:
M. Lehning
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