written January 10th 2000  back to my CV     back to my home page  

Snow cover dynamic and one dimensional energy fluxes

at the Schauinsland, Black Forest (Germany)

Poster Abstract
Stefan Vogel
Department of Geological Sciences - Univeristy of Kentucky
swvoge2@pop.uky.edu

In winter 1996/97 an investigation about the snow cover dynamic and one dimensional energy fluxes at a site in the Black Forest was held at the Schauinsland, Freiburg.
The time period of the investigation was from the 25th of November 1996 until the 5th of March 1997. During this period the snow cover dynamic was observed and meteorological data's were collected by an automatic weather station (AWS). Meteorological data's are available for the period between the 13th of December 1996 and the 5th of March 1997.
The meteorological data were used to calculate the energy balance.
The energy balance of the snow pack (Q) is determined by the net radiation (R), the latent heat flux (H) and the sensible heat flux (E). For calculation of the snowmelt the soil heat flux (Hs) was added.


Q = R + H + E + Hs

Net radiation (R) and soil heat flux (Hs) was measured directly. The turbulent heat fluxes were computed from wind speed data, humidity gradients and temperature gradients by differential bulk approach (Braithwater, 1995).
The modelled energy balance was used to estimate the possible or modelled snowmelt (run off). Finally to proof the energy balance, the possible snowmelt was computed for each period between two snow pit measurements and compared with the measured.
Differences between the possible snowmelt and the measured can be attributed to additional energy supply from precipitation or to the possible retention volume of a snow cover. An example for additional energy fluxes from precipitation is the first melting period from 13th until 24th of December 1996. During this period, with relatively high temperatures, the magnitude of snowmelt calculated from additional energy flux through rain (measured rainfall by an average temperature of +4°C), will cover the difference between calculated and measured snowmelt.
For both melting periods (6th until 13th and 18th until 25th February) an overestimation of calculated snowmelt is followed by an underestimation. The overestimation of calculated snowmelt corresponds to the possible retention volume of the snow cover (Wilhem, 1974). For both periods the overall magnitude of the calculated snowmelt is close to the measured one. For the last melting period (18th until 25th February) the high overestimation of calculated snowmelt is due to a low albedo of pure soil after all snow was melted. For the whole investigation period the total amount of calculated snowmelt of 253mm correspond very well with the measured snowmelt of 251mm, even this shows too fine accuracy.
Overall even the model does not include processes within the snow cover it yields good results computing the energy balance and also for calculation of mass balance.


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