One-dimensional energy fluxes of a snow cover in winter 1996/97 at the Schauinsland, Black-Forest (Germany)

An investigation into the snow cover dynamic and the one dimensional energy fluxes at a test site in the Black Forest was carried out at the Schauinsland, Freiburg, in winter 1996/97. The time period of the investigation was from 25^th November 1996 until 5^th March 1997. During this period the snow cover changes were observed and meteorological data were sampled at an automatic weather station (AWS). The meteorological data were used to calculate the energy balance. The atmospheric energy balance of the snow surface (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 (H_s) was added.

Q         =          R + H + E + H_s

Net radiation (R) and soil heat flux (H_s) were measured directly. The turbulent heat fluxes were computed from wind speed, humidity gradients and temperature gradients by differential bulk approach. The modelled energy balance was used to compute snowmelt. This was compared to the snowmelt as observed for each time period between two snow pit measurements. Snow pit observations were carried out approximately every two to three days.

Differences between computed and observed snowmelt can be attributed to additional energy input from precipitation or to the retention volume of the snow cover. Additional energy input from precipitation e.g. caused snowmelt from 13^th to 24^th December 1996. During this period, the difference between computed and measured snowmelt corresponds to the energy surplus supplied by rain.

During two periods with considerable snow melt (6^th to 13^th and 18^th to 25^th February) overestimation of snowmelt during the initial phase of the melting period was compensated by underestimation during the on-going of melting. The amount of this mismatch corresponds to the retention volume of the snow cover. During both periods the overall amount of the computed snowmelt matches the measured snowmelt.

The extraordinary overestimation of calculated snowmelt during the final melting period (18^th until 25^th February) is due to low albedo of bare soil after the last snow patches had melted away.

The total amount of calculated snowmelt of 253 mm water equivalent corresponds very well to the total measured snow volume of 251 mm water equivalent. Although this model does not include snow pack processes it returns reasonable results for seasonal snow melt and seasonal energy balance estimates at the study site.