Exploring the Unknown - NASA's History Office

EXPLORING THE UNKNOWN 181
Colour contrasts of objects on the ground tend to be suppressed in at least two ways:
selective scattering of the bluer components by atmospheric molecules, and “dilution” of
colours by the white diffuse component contributed by the non-selective foreign particle
scattering in the atmosphere.
The effect of the first type of scattering is to deplete the blue colours relatively more
than the longer wave-lengths. The over-all effect is to emphasize red [274] colour components
of the objects on the ground, as compared to the blue components; and to screen
both with diffuse light consisting of a relatively large blue component mixed with white
light. The over-all result would be to give a bluish tinge to what is seen, since the blue scattered
from the incident solar beam would more than make up for the blue-depletion of
light coming from the ground.
As to the colour of the sky on the horizon, we might expect that there would be a grey
layer, corresponding to the atmosphere say in the lower 10,000 ft., with an upper thin blue
region in the region of substantial Rayleigh scattering, and black above that.
Thus, as a result of all these calculations, a reasonable picture was obtained of the surface
features of the Earth under normal conditions of June 21 ground cover illumination,
albedo and atmospheric effects, but without clouds. Over this chart was sketched a hypothetical
cloud pattern normally associated with certain atmospheric disturbances. Albedo
values were assigned to various cloud types and their brightness as computed. These “disturbances”
included the following:—
(a) A cyclone family of three storms in various stages of development extending from
Hudson Bay south-westward to Texas.
(b) The north-eastern part of another such cyclone family whose oldest member is in
the Gulf of Alaska, the remaining members to the southwest being invisible.
(c) A fully developed hurricane embedded in “streets” of trade cumuli in the West
Indies.
(d) The Intertropic Convergence Zone (or Equatorial Front)—a zone of interaction
between the north-east trades of the northern hemisphere and the south-east
trades of the southern hemisphere—extending west of Isthmus of Panama to the
mid-Pacific.
(e) A “line-squall”—favourite breeding-ground of severe wind storms and tornadoes—in
the eastern U.S. moving ahead of the cold front and surrounded on
both sides by the cauliflowerlike cumulus congestus.
(f) Scattered cumulus clouds of varying thicknesses over the heated land areas—
especially in the mountains and other areas where dynamic effects encourage the
lifting of air in vertical columns.
(g) Altocumulus lenticularis or lens-shaped clouds formed by lifting of layers of moist
air over mountains and usually found where the “jetstream” crosses mountains, as
over the northern Canadian Rockies.
(h) Low stratus and fog found off the southern and lower California coasts, over the
Great Lakes, the Newfoundland area, formed by passage of warm moist air over
cold surfaces.
The cumulus cloud systems over the oceans will tend to fall in fairly regular patterns
or “streets”—even more so than was observed over the rough terrain in the V2 picture.
The regularity of the ocean cloud systems in the present sketch is probably exaggerated,
but its breakdown into a more irregular pattern over land is believed to be real. The centres
of the anticyclonic or “high pressure” areas are marked by little or no cloud.
[275] This then is the hypothetical picture visible from the 4,000-mile high vehicle over
Amarillo, Texas. Some of these clouds, such as the Trade Cumuli, could undoubtedly be
observed on almost any day and others, such as the hurricane, seen only rarely. The
cyclone families would be observed daily, but their location, the number of individual