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Investigation 3 – PreLab









Astronomers determine the composition of a planet, its atmosphere, and its moons. Interestingly, astronomers continually contend with Earth’s atmosphere. It is a notoriously unpredictable and limiting factor in obtaining fine views of the planets and stars.


This Investigation is designed to help you to answer the following Focus Questions:

  • What factors are necessary for precipitation to form along fronts? 
  • What changes in atmospheric pressure occur with the passing of a cold or warm front? I

Note: These questions are located in your SDR at the beginning and end of the Investigation.


As a class, read the Background(s) in the Investigation. When finished, discuss the following concepts as a class:

  • Air masses are large bodies of air that develop over areas of the Earth where the air is relatively calm and there are few winds.
  • Air masses tend to form in the polar and tropical regions of the Earth and take on the temperature and humidity characteristics of the surface over which they develop.
  • The air masses that form over water usually contain more water or moisture than the air masses that form over land.
  • Meteorologists tend to classify the major air masses according to the following labels:

ATMOS 3 Pre Table

  • Air masses are moved around the Earth by upper atmosphere winds such as the jet stream as well as winds surrounding low and high-pressure systems.
  • When air masses of different temperatures collide, a front is formed.
  • Fronts represent the boundaries between warm and cold air masses. In a cold front, a cold air mass moves in behind a warmer air mass. In a warm air front, a warm air mass moves in behind a colder air mass.
  • Cold and warm front are represented by different symbols on a weather map.
    • A cold front is represented by a solid line with triangles. The triangles point in the direction of the warmer air and the direction in which the front is moving.
    • A warm front is represented by a solid line with semi-circles pointing in the direction of the colder air and in the direction in which the front is moving.

ATMOS 3 Pre Map



The following list includes Key Terms that are introduced in the Investigation Background(s). They should be used, as appropriate, by teachers and students during everyday classroom discourse.

  • air mass
  • front
  • cold front
  • warm front
  • evaporation
  • condensation
  • precipitation

Note: Definitions of these terms can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.


  • Recall what you have already learned about atmospheric and barometric pressure from the experiments in Investigation Two. Discussing the following questions. Describe the air movements that accompany high and low-pressure systems.
    • What types of air movement are observed with areas of high and low pressure?
    • How are changes in atmospheric pressure measured?
  • Think about other symbols that you may see on weather maps or other terms that you may hear in weather forecasts. For example, terms like warm air mass, cold air mass, cold front, and warm front.
  • Assess your prior knowledge and understanding of the Background information to predict the answers to the following questions:

ATMOS 3 PreLab Prediction Box

  • Play the video below. Remember to follow along with your SDR and make any notes that you think might be helpful in the lab.
  • After the video, divide into lab groups to discuss strategy for the lab. For example, you may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow you to anticipate the laboratory experience you will soon encounter. You should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video.


You should review the Investigation and video in preparation for the Lab.