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.
CLIMATE AND WEATHER 263 6. Explain the equable climates on the western coast of North America. 7. What is the cause of ocean currents? 8. At what time, day or night, do breezes usually blow from the ocean to the land, and why? 9. At what time, day or night, do breezes blow down mountain canyons, and why? 10. How do breezes from the land and sea change from winter to summer? 11. What is meant by relative humidity? How is it measured? Of what value is this information? 12. Why is Death Valley so dry? 13. Account for the Nevada desert. 14. Why does snow melt so rapidly in a moist warm breeze? 15. Discuss the factors which are the basis for climate and weather. 16. Differentiate between whirlwinds, tornadoes, hurricanes, and cyclones. 17. Discuss the causes of rain, snow, fog, lightning storms, and tornadoes. 18. Explain how convection currents are produced. 19. Why do we have less frost in cloudy weather than on clear nights? 20. Discuss the formation of hail. 21. What are the two causes of the circulation of the atmosphere? 22. What is the dew point, and how is it obtained? 23. W'hat is the cause of the excellent climate of Florida? 24. Why do the states along the eastern seaboard experience weather so different from that of the Pacific coast states?