Ice Station Weddell
140
25 February - 29 May 1992
120
100
80
Counts
60
40
20
0
0
1
2
3
4
5
6
7
8
9
10
Total Clouds (tenths)
Figure 4. Histogram of total cloud amount observed during the drift of Ice
Station Weddell from 25 February through 29 May 1992.
for remote sensing and numerical modeling, especially when cloud amount is an
external parameter of the model.
Another no less important problem in developing climatic sea ice models and
using them for numerical experiments is adequately accounting for cloud amount
in calculations of shortwave and longwave radiation (Curry and Ebert 1990,
Doronin and Kheisin 1975). About 10 empirical formulas exist for estimating
incoming longwave radiation from measured surface-layer temperature, charac-
teristics of the clouds (i.e., amount and type of clouds), and, sometimes, surface-
layer humidity. Recently, Knig-Langlo and Augstein (1994) and Key et al. (1996)
reviewed some of these parameterizations and evaluated their accuracy in account-
ing for incoming longwave radiation in polar regions. The meteorological data they
used for their evaluations came from Resolute (Canada), Barrow (Alaska), Ny-
lesund (Spitzbergen), and Georg von Neumayer Station in Antarctica.
Here we consider additional data collected on the RussianAmerican drifting
station Weddell-1 (or Ice Station Weddell, ISW) when that station drifted through
the western Weddell Sea in 1992 (Andreas et al. 1992). On ISW, we used both Rus-
sian and American instruments to measure the hourly averaged components of
the radiation budget during the Antarctic fall and winter (February through May)
(Claffey et al. 1995). In the second part of this report, we compare the incoming
longwave radiation data collected on ISW with the most frequently used
parameterizations for incoming longwave radiation.
Obviously, one of the major applications for a parameterization of incoming
longwave radiation is for estimating that component of the surface heat budget in
models of sea ice in polar regions. Therefore, we report a number of numerical
experiments done with a quasi-stationary, zero-dimensional thermodynamic sea
ice model similar to Semtner's (1976). Our purpose is to study the influence of
various methods for describing meteorological information and various parame-
terizations for the longwave radiation balance on the equilibrium thickness of sea
ice in the Arctic.
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