Figure 11. Temporal variability of
total cloud amount for November
1982 on North Pole 25. The traces
show 1) the 3-hour cloud obser-
vations averaged to daily values,
2) cloud amount estimates based
on eq 4 using daily averaged tem-
perature, and 3) cloud amounts
estimated using monthly cloud
data interpolated to daily values
over three months.
Figure 12. Temporal variability of the daily averaged surface-
layer air temperature and the incoming longwave radiation
for November 1982 on North Pole 25. The computed values
of Fdn are based on eq 12 using 1) 3-hour cloud observations
averaged to daily values, 2) monthly cloud data interpolated
months, and 3) daily averaged cloud data estimated using eq 4.
culations of longwave radiation for each winter month on North Pole 25 based on
the KL&A parameterization, explains the good agreement among these three cases.
We see in Table 10 and in Figure 12 that, despite the essential differences in the
time series of cloud amounts used in the calculations (Fig. 11), the time series of
calculated Fdn values correspond well with each other, both on average and in terms
of the linear correlation coefficient. Although this good agreement may, at first,
seem paradoxical, the formula used to estimate Fdn explains it. To obtain the
longwave fluxes in Table 10 and in Figures 12, we used--from eq 6 and 12--
Fdn = σ T 4 aK + bK n3 .
Thus, the air temperature T dominates the calculation. But remember, the correla-
tion between T and n is also high. Consequently, because the surface-layer air tem-