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| Titel |
Seasonal and diurnal cycles of liquid water in snow |
| VerfasserIn |
Achim Heilig, Christoph Mitterer, Lino Schmid, Hans-Peter Marshall, Jürg Schweizer, Robert Okorn, Olaf Eisen |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250098748
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| Publikation (Nr.) |
 EGU/EGU2014-14452.pdf |
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| Zusammenfassung |
| The combination of upward-looking ground-penetrating radar (upGPR), automatic weather
station (AWS) and lysimeter allows for continuous monitoring of bulk volumetric liquid
water content (θw) within the snowpack and direct comparison with measurements of the
corresponding outflow. The AWS data can be utilized to calculate energy fluxes
between atmosphere and snowpack at the location of the station. While combining
all data sets, we were able to quantify diurnal and seasonal changes in residual
water content and relate modeled energy fluxes to water outflow. Since upGPR is a
non-destructive monitoring technique, it is possible to continuously observe the
snowpack and results are not biased through spatial variability of pit locations. Data
analysis conducted for three consecutive years at the flat test site Weissfluhjoch,
Davos, Switzerland showed that diurnal θw variations never exceeded 2%. Without
regard to days with new snow accumulation or refreezing, the diurnal patterns in θw
were very similar, with always daily peaks in the late afternoon (at about 17:00h) at
the site. Although θw values varied during a day up to 2%, the gradients during
the season were very small. In 2012, for the whole melting period (>100 days),
increases in θw from day to day were 0.4% liquid water content on average. After the
snowpack has become isothermal, positive energy fluxes result in outflow and increase
the residual water content (θr). Our data showed that as long as potential melt -
calculated for the determined energy fluxes - was exceeding measured outflow, θr values
were increasing but only until reaching a certain threshold. For all three years,
the thresholds were similar at about θr=4–5%. Only shortly before full ablation,
these thresholds were surpassed. In two sloped test sites (about 22 degree slope
angle) in Boise, Idaho, USA and above Davos, we installed upGPR systems as well.
AWS data and energy-flux calculations for both slopes were extrapolated for the
respective aspect and slope angle. Our data showed that snow stratigraphy highly
influences θr in slopes. As long as e.g. crusts ponded the vertical water flow, residual
θw of the whole snowpack was fairly low ( |
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