Each statement represents the primary learning objective for the corresponding section heading within this chapter.  After you complete this chapter, you should be able to:

• Explain the roles of adiabatic cooling and cloud condensation nuclei in cloud formation (Section 5.1).
  
  

• Name and describe the 10 basic cloud types, based on form and height. Contrast nimbostratus and cumulonimbus clouds and their associated weather (Section 5.2).
  
  

• Identify the basic types of fog and describe how each forms (Section 5.3).
  
  

• Describe the Bergeron process and explain how it differs from the collision–coalescence process (Section 5.4).
  
  

• Describe the atmospheric conditions that produce rain, snow, sleet, freezing rain, and hail (Section 5.5).
  
  

• Describe the instruments used to measure precipitation, including the standard rain gauge, snow pillow, and weather radar (Section 5.6).
  
  

• Discuss several ways that humans attempt to modify the weather (Section 5.7).

Clouds, fog, and the various forms of precipitation are among the most observable weather phenomena. The primary focus of this chapter is to provide a basic understanding of each. In addition to learning how clouds are classified and named, you will learn that the formation of an average raindrop involves complex processes requiring water from roughly a million tiny water droplets.

Cloud Formation

• How Does Air Reach Saturation?

• The Role of Condensation Nuclei

• Growth of Cloud Droplets

Cloud Classification

• Cloud Forms

• Cloud Height

• High Clouds

• Middle Clouds

• Low Clouds

• Clouds of Vertical Development

• Cloud Varieties

Types of Fog

• Fogs Formed by Cooling

  • Radiation Fog

  • Advection Fog

  • Upslope Fog

• Evaporation Fogs

  • Steam Fog

  • Frontal (Precipitation) Fog

How Precipitation Forms

• Precipitation from Cold Clouds: The Bergeron Process

  • Supercooled Water

  • Saturation Vapor Pressure over Water Versus over Ice

  • How the Bergeron Process Generates Precipitation

• Precipitation from Warm Clouds: The Collision-Coalescence Process

  • Cloud Droplet Size and Fall Velocities

  • Hoiw Do Cloud Droplets Coalesce?

Forms of Precipitation

• Rain

• Snow

• Sleet and Freezing Rain

• Hail

• Rime

Precipitation Measurement

• Measuring Rainfall

• Measuring Snowfall

• Precipitation Tracking by Weather Radar

Planned and Inadvertent Weather Modification

• Planned Weather Modification

  • Snow and Rain Making

  • Fog and Stratus Cloud Dispersal

  • Hail Suppression

  • Frost Prevention

• Inadvertent Weather Modification

  • Effects of Large Transportation Corridors

  • Urban Effects