Explain why clouds form in rising air

Question

What will be an ideal response?

Answer 1

ANSWER: ?Clouds form either by: (1) cooling—air is cooled below its saturation point (dew point) or (2) evaporation and mixing—water vapor is added to the air by evaporation and moist air mixes with relatively dry air. In general, air temperature within the troposphere decreases with altitude, hence it is expected to have clouds forming as air rises. However, for cloud formation to occur condensation nuclei must be present in the atmosphere. The condensation nuclei most favorable for producing clouds (called cloud condensation nuclei) have radii of 0.1 µm or more. Usually, between 100 and 1000 nuclei of this size exist in a cubic centimeter of air. These particles enter the atmosphere in a variety of ways: dust, volcanoes, factory smoke, forest fires, salt from ocean spray, and even sulfate particles emitted by phytoplankton in the oceans. In fact, studies show that sulfates provide the major source of cloud condensation nuclei in the marine atmosphere. Because most particles are released into the atmosphere near the ground, the largest concentrations of nuclei are observed in the lower atmosphere near Earth's surface. Condensation nuclei are extremely light (many have a mass less than one-trillionth of a gram), so can remain suspended in the air for many days.