On the radiation characteristics of Antarctic Sea Ice |
| |
Authors: | Gerd Wendler Blake Moore Dorte Dissing John Kelley |
| |
Institution: | 1. Geophysical Institute , University of Alaska , Fairbanks, Alaska, 99775, USA E-mail: gerd@gi.alaska.edu;2. Geophysical Institute , University of Alaska , Fairbanks, Alaska, 99775, USA |
| |
Abstract: | Abstract Radiative measurements were carried out continuously during a cruise from Australia to Antarctica during austral summer 1995/96. Both shortwave and longwave radiative fluxes were measured. Some of the results are: -
The incoming solar radiation had a mean value of 217 W m–2; this was a relatively weak value due to the large amount of fractional cloud cover observed. The sun was, for a large part of the trip, above the horizon for 24 hours a day. -
The reflectivity varied widely, not only as a function of sea‐ice concentration, but also as a function of ice type. -
Snow covered pack ice gave the highest albedo values (<70%), while flooded sea ice and thin ice reflected much less (<30%). -
For each sea‐ice type, short term observations showed a good relationship between albedo and ice concentration. -
The albedo increased with decreasing solar elevation. -
The net longwave radiation was negative (mean –27 W m–2); this small absolute value is due to a high amount of fractional cloud cover. There was a weak diurnal variation with a maximum loss (–33 W m–2) in the early afternoon. -
On the average, the net radiation was positive for 17 hours, and negative for 7 hours a day. However, the duration of a positive balance depended strongly on the surface albedo. -
For the observed albedo values, modelling results showed that the net radiation was always positive when averaged over a day. The magnitude, however, depended strongly on the surface albedo, varying by more than the factor of three. |
| |
Keywords: | |
|
|