Geoscience Reference
In-Depth Information
Figure 5.1.
(
Cont.
)
elevation Greenland ice sheet peak at more than 360 W m
−2
, and values in excess of
300 W m
−2
are found near the Pole. June fluxes of 200-220 W m
−2
characterize the
Atlantic side in the Norwegian and Barents seas, where cloud cover is both thick
and extensive.
5.4
Surface Albedo
5.4.1
Definition
The “true” surface albedo refers to the ratio of solar radiation reflected by a surface
to the incident direct beam illumination. This is termed the “directional-hemispheric
reflectance” because the downwelling term is the direct beam irradiance at a speci-
fied angle and the reflected flux is integrated over the upward hemisphere. This dif-
fers from the albedo measured near the earth's surface (examined here) where the
downward flux contains a significant diffuse component (especially under cloud
cover). The albedo measured near the earth's surface is termed the bihemispherical
