Untersuchungen zum Energieumsats in der Ablationszone des grönlandischen Indlandeises: Nachtrag.

Resumé

1. Radiation budget in the ablation area
On account of new calibration resuits for the Lupolen instrument in the longwave spectral range, the radiation fluxes of the series of measurements made in the ablation area in 1959 were newly calculated. The complexity of the net radiation balance in the ablation area is determined by the large range of albedo values (46% -85%). At high albedo (> 70 ob), the net radiation balance increases with cloudiness, at low albedo it decreascs with cloudiness. In the net radiation balance the influence of albedo prevails so that there exists a positive correlation bctwccn the net radiation balance and short-wave radiation balance. In the accumulation area, however, there occurs a positive correlation between the net radiation balance and the long-wave radiation balance because of the constantly high albedo.

2. Comparison of ablation and climatic elements
Ice ablation and climatic elements during the measurement period were compared and discussed. The mean values of the net radiation balance, air temperature, vapor pressure, wind velocity, and increase of ice temperature were determined for three ranges of ice ablation. It can be confirmed that high ablation values cor respond to high values of net radiation balance, air temperature, and wind velocity, whereas vapor pressure and heating of the ice do not show the same trend. The energy budget is given for three ranges of ablation. The increase of the convective term with increasing ablation is striking.

3. Ablation and energy budget
The components of the energy budget are given for the entire times of measurements divided into various periods. Measured and calculated ablation values are compared, showing good agreement. The marked differences in the energy budget of an ice and snow surface are treated quantitatively, as well as the differences in the ablation periods of midsummer and late summer. The energy necessary for melting and heating the ice on average is contributed by the net radiation balance ( 83%) and convective heat flux (17%), 26% of which are sensible heat flux, 3% are positive heat flux and -12% are negative latent heat flux. The mass loss owing
to evaporation amounts to no more than 2% of the net ablation.

4. Comparison of energy balance and ablation at various altitudes
The few data of net ablation of ice at various altitudes were compared with values of the energy budget. Measurements of air temperature at the Jakobshavn shore station were used for developing a method of estimating the net ablation of ice by determining the number of days with ablation.