HR: 17:15h
AN: C34A-06    [Abstracts]
TI: Observations and Processes Near the Snow-Air Interface: Insights Gained from New and Comparative Sensor Systems in View of Snow Surface Energy Balance Closure
AU: * Huwald, H
EM: Hendrik.Huwald@epfl.ch
AF: Ecole Polytechnique Fédérale de Lausanne, GR A0 402, Station 2, Lausanne, CH-1015, Switzerland
AU: Selker, J S
EM: selkerj@engr.orst.edu
AF: Oregon State University, Oregon State University, Corvallis, OR 97331, United States
AU: Calaf-Bracons, M
EM: marc.calaf@epfl.ch
AF: Ecole Polytechnique Fédérale de Lausanne, GR A0 402, Station 2, Lausanne, CH-1015, Switzerland
AU: Parlange, M B
EM: Marc.Parlange@epfl.ch
AF: Ecole Polytechnique Fédérale de Lausanne, GR A0 402, Station 2, Lausanne, CH-1015, Switzerland
AB: Global warming drastically affects the seasonal snow cover in high altitude regions. The thermodynamic evolution of the snow pack is mainly controlled by the surface energy balance, however, most studies to date fail to close this budget on short time scales when using measurements of all its components. Also dynamic processes such as air movement in the snow pack associated with air exchange and the snow-atmosphere interface have to be taken into account. To investigate snow-atmosphere interaction, measurements of radiative and turbulent heat fluxes, and other meteorological quantities were obtained over a snow-covered glacier in the Swiss Alps during winter 2007. Humidity, air, surface, and snow temperature – quantities required to calculate energy fluxes for the surface energy budget – were measured with different sensors and techniques. Data revealed significant discrepancies between individual measurements at a location and time mainly due to solar heating of the sensors. We show that even shielded sensors overestimate air temperature during the day when compared to a radiation-independent reference sensor (sonic anemometer). Subsurface heat flux was determined from snow internal temperature and density data. High resolution temperature profiles were measured in the snow using traditional (thermocouple) and novel fiber optic distributed temperature instrumentation. To better understand the rate of gas exchange with the atmosphere controlling latent heat transport in the snow associated to phase changes (sublimation/deposition), air movement in the snow was investigated with using a new in-situ carbon monoxide trace gas measurement system providing high-resolution observation of snow transport process without gas extraction.
UR: http://eflum.epfl.ch
DE: 0764 Energy balance
DE: 0794 Instruments and techniques
DE: 1840 Hydrometeorology
SC: Cryosphere [C]
MN: 2007 Fall Meeting