ARCTIC WEATHER PECULIARITIES. The strong temperature inversions present over the Arctic during much of the winter causes several interesting phenomena. Sound tends to carry great distances under these inversions. On some days, when the inversion is very strong, human voices can be heard over extremely long distances as compared to the normal range of the voice. Light rays are bent as they pass through the inversion at low angles. This may cause the appearance above the horizon of objects that are normally below the horizon. This effect, known as looming, is a form of mirage. Mirages of the type that distort the apparent shape of the Sun, Moon, or other objects near the horizon are com-mon under inversion conditions.

One of the most interesting phenomena in the Arctic is aurora borealis (northern lights). These lights are by no means confined to the Arc-tic but are brightest at the arctic locations. Their intensity varies from a faint glow on cer-tain nights to a glow which illuminates the sur-face of the Earth with light almost equal to that of the light from a full moon. The reactions resulting in the auroral glow have been observed to reach a maximum at an altitude of approx-imately 300,000 feet.

The amount of light reflected from a snow-covered surface is much greater than the amount reflected from the darker surfaces of the mid-dle latitudes. As a result, useful illumination from equal sources is greater in the Arctic than in lower latitudes. When the sun is shining, suf-ficient light is often reflected from the snow sur-face to nearly obliterate shadows. This causes a lack of contrast which, in turn, results in an in-ability to distinguish outlines of terrain or objects even at short distances. The landscape may merge into a featureless grayish-white field. Dark mountains in the distance may be easily recognized, but a crevasse immediately ahead may be obscured by the lack of contrast. The situation is even worse when the unbroken snow cover is combined with a uniformly overcast sky and the light from the sky is about equal to that reflected from the snow cover. In this situation, all sense of depth and orientation is lost in what appears to be a uniformly white glow; the term for this optical phenomenon is whiteout.

Pilots have reported that the light from a half-moon over a snow-covered field is suf-ficient for landing aircraft at night. It is pos-sible to read a newspaper on occasions by the illumination from a full moon in the Arctic. Even the illumination from the stars creates visibility far beyond what one would expect elsewhere. It is only during periods of heavy cloud cover that the night darkness begins to approach the degree of darkness in lower latitudes. In lower latitudes, south of 65 north latitude, there are long periods of moonlight, since the Moon may stay above the horizon for several days at a time.

Many of the same peculiarities prevalent over the arctic regions are also present in the antarctic. For instance, the aurora borealis has its counterpart in the Southern Hemisphere, called aurora australis. The same restrictions to visibility exist over the antarctic regions as over the Arctic. Some other characteristics of the antarctic regions are as follows:

Precipitation occurs in all seasons, with the maximum occurring in summer. The amount of precipitation decreases poleward from the coast.

Temperatures are extremely low. The low-est temperature in the world, 127F, was recorded at Vostok, Antarctica. In the winter, temperatures decrease from the coast to the pole, but there is some doubt that this is true in the summer. The annual variation of temperature as indicated by Macmurdo station shows the maximum in January and the min-imum in early September. A peculiar, and to date unexplained, feature of antarctic temper-ature variations during the antarctic night is the occurrence of maximum temperatures on cloudless days in the early hours after mid-night. On cloudy days, however, the day is warmer than the night.

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