Explain why altocumulus clouds might be observed at 6400 m ...

[PhilipSeeMore]

Explain why altocumulus clouds might be observed at 6400 m (21,000 ft) above the surface in Mexico City, Mexico, but never at that altitude above Fairbanks, Alaska.
   
  What will be an ideal response?

Question 2

Explain how dew, frozen dew, and visible frost form.
  What will be an ideal response?

[tdewitt]

Answer to Question 1

ANSWER: Air temperatures aloft are much lower above polar latitudes than above subtropical latitudes. Altocumulus clouds usually contain liquid water. Over polar latitudes at 6400 m (21,000 feet), temperatures are generally low enough to freeze all liquid water. Therefore, the very cold air will produce a thin, ice crystal (cirriform) cloud. At 21,000 feet above the tropics and subtropics temperatures are not low enough to freeze all liquid water; consequently, thicker middle clouds may form at that altitude.

Answer to Question 2

ANSWER: Dew forms when the air cools to the dew point, the temperature at which saturation occurs. Frozen dew forms if the air temperature drops to freezing or below. The dew will freeze, becoming tiny beads of ice. Visible frost forms on cold, clear, calm mornings when the dew-point temperature is at or below freezing. When the air temperature cools to the dew point (now called the frost point) and further cooling occurs, water vapor can change directly to ice without becoming a liquid firsta process called deposition.