Geography 101 The Physical Environment
                                                          Announcements |   Course Outline  |   TPE: Text 
                                                                   Calendar  |  Syllabus    |   Study Aids |   Grades | Blog   

Atmospheric Structure and
Composition

Introduction

Our atmosphere is comprised by a dynamic mixture of gases that envelop the earth. Two gases, nitrogen and oxygen make up most of the atmosphere by volume. They are indeed important for maintaining life and driving a number of processes near the surface of the earth. Many of the so called "minor gases" play an equally important role in the earth system. The minor gases include those that have a significant impact on the heat budget and the availability of moisture across the earth. The atmosphere is not a homogeneous mass of gases, but has a layered structure as defined by vertical temperature changes. In this lecture we'll look at the significance of the major and minor gases and describe the vertical structure of the earth's atmosphere.

Atmospheric Composition

Permanent Gases (% by volume)

• Nitrogen 78

• Oxygen 21

Variable Gases (% by volume)

• Carbon Dioxide - Greenhouse Gas 

  • (See Greenhouse effect animation)

• Methane - Greenhouse Gas

• Ozone - Absorbs UV; eye and respiratory irritant; damages plants

• Water vapor  Greenhouse Gas; absorbs long-wave radiation

• Particulates - Absorbs long-wave or reflects short-wave radiation; condensation nuclei

Atmospheric Structure

• Atmosphere subdivided on the basis of temperature change

Troposphere

• Normal (.65^o C /100 m) vs. Environmental Lapse Rate of Temperature
   

Tropopause

Stratosphere

• Inverted lapse rate of temperature - temperature increases with increasing elevation.

Optional Reading

• "Cattle Contribute to Global Warming" - Read about the contribution that cattle make to greenhouse gases in Brazil.

• "Kangaroos offer clue to global warming" - from the BBC
  

Optional Audio Program

• "Ozone Layer" Listen to this NPR segment from May 2000 about the ozone hole over the Arctic.

Can you....

• describe the significance of the variable gases to the earth's atmospheric environment?

• describe characteristics of the troposphere, tropopause, and stratosphere?