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Unit 4: Temperature-Moisture Relationship

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Temperature & Heat   ::   Temperature & Altitude   ::   Atmospheric Moisture   ::   Relative Humidity   ::   Clouds   ::   Exercises


Upon completion of this unit you will be expected to:

  • Compare the effects of daytime solar radiation, and nighttime heat losses from various topographic surfaces.
  • Explain temperature lapse rates in the atmosphere, and give the theoretical values for dry, wet, and normal lapse rates.
  • Explain the relationship between temperature, dew point, and relative humidity.
  • Give the dry bulb and wet bulb temperatures, determine relative humidity and dew point using appropriate psychrometric tables.
  • Determine relative humidities at various temperatures within a fixed or stationary air mass when given one temperature and corresponding relative humidity.
  • Give four groups of clouds, their approximate base height, and explain how these clouds are formed.
  • Given six indicator cloud types, describe their probable effect on fire weather.


Weather is the most variable and often the most critical determinant of fire behavior. This is the first of several units that will deal with weather and its relationship to fire behavior. This unit will discuss atmospheric temperatures, moisture, and the relationship between these two elements.
You should be familiar with the atmosphere that surrounds the earth and its life-supporting elements of oxygen, moisture, and other gases that affect our activities and well-being. This atmosphere is very dynamic, with conditions changing from moment to moment, that can impact on our activities on very short notice.
These short term atmospheric variations are what we call weather. To most people, weather is thought of in terms of temperature, humidity, precipitation, cloudiness, sunshine, visibility, and wind. The fire manager is concerned with all of these factors, since his successes and failures are often dependent on his keeping current with the weather. An understanding of weather processes and the ability to observe and interpret atmospheric conditions are of great advantage to the fire manager.

Copyright 2008, by the Contributing Authors. Cite/attribute Resource . admin. (2005, September 28). Unit 4: Temperature-Moisture Relationship. Retrieved January 07, 2011, from Free Online Course Materials — USU OpenCourseWare Web site: This work is licensed under a Creative Commons License Creative Commons License