Man's physical universe

xanabras

262 PHYSICAL LIMITATIONS HAVE BEEN OVERCOME

out of doors with an inch-thick layer of ice. On Monday the storm

changed to a "northeaster," and during Monday night branches and

trees were broken down by the heavy layers of ice and the strong

winds. Damage to the extent of millions of dollars was wrought on

forests and orchards. Telephone, telegraph, and lighting services

stopped as the wires broke under the weight of the two-inch coating

of ice. In some places every pole in mile-long stretches of telephone

lines was felled.

The storm reached its climax with a violent thunderstorm and pink

lightning.

Sleet and Snow Are Common Forms of Precipitation.

Sleet differs from hail in that it is not built up in a layer formation

but is produced by the freezing of raindrops as they fall through a

stratum of cold air below the cloud. Snow is formed, as is rain, by

the cooling of moist air, but the condensation occurs below the freezing-point

of water. Graupel is a white pellet which is considered to be

formed by the partial thawing of snow in a warm layer of air, followed

by freezing in a lower cold layer of air. The snowflakes grow in beautiful

hexagonal crystals of myriad forms. Record snowfalls of three to

five feet have occurred; but inasmuch as fallen snow is mostly air, this

amount of snow does not represent much water. The composition of

snow varies from one to thirty parts of air to one part of water; on the

average, ten inches of snow will give one inch of water when melted.

Inasmuch as dark-colored or black surfaces absorb the sun's heat,

it is easy to understand that snow covered with soot or ashes will melt

much more rapidly than clean white surfaces which reflect most of the

radiant energy of the sun.

Heat is given off when condensation takes place, and snow therefore

melts very rapidly in a moist warm breeze, because the cold snow

causes the moisture in the air to condense. The condensation of moisture

equivalent to an inch of rain would melt thirty times as much

snow as would the same amount of rain after it was condensed.

It has been suggested that much of the energy of hurricanes is

produced by the heat liberated through the condensation of the huge

amounts of rain that accompany such storms.

STUDY QUESTIONS

1. DiflFerentiate between weather and climate.

2. Describe an ideal climate.

3. Criticize the climate of your own home locality.

4. What causes the widespread variations in climate?

5. Where are the extremes of continental climatic conditions found? Explain.

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