Chapter 3 Introduction to the Atmosphere

 Supplies oxygen for humans & animals  Supplies carbon dioxide (CO 2 ) for plants  Helps maintain water supply  Insulates Earth from extreme temperatures  Insulates Earth from ultraviolet radiation - (UV) rays Atmosphere makes life possible on Earth

Introduction to the Atmosphere  Composition of the Atmosphere  Vertical Structure of the Atmosphere  The Ozone Problem  Weather and Climate

Air  Air is not a gas; it is a mixture of gases  2 main gases are oxygen and nitrogen  Pure air is colorless and odorless  Clouds are made up primarily of water vapor

Composition of the Atmosphere 3 Main Gases: –Nitrogen = 78 –Oxygen = 21 –Argon = 1 These are approximate numbers that we will use in this class.

Atmospheric Gases

Particulates  Larger particulates are water and ice  Dust and pollen  Chemicals  Aerosols  Some are natural – some are human source  i.e. industrial, automotive, fires Particulate matter in the atmosphere is from both natural and human sources. For example: pollen is natural and automotive exhaust (CO 2 ) is human.

Particulates  The atmosphere provides vertical and horizontal transport of particulates  Particulates can be transported great distances – even globally by the atmosphere  Particulates affect weather and climate: Cloud formation Absorption & reflection of sunlight Earth Atmosphere

Dust Storms Atmospheric Particulates Dodge City, Kansas May 29, 2004 Libya-Sicily May 29, 2004

Mt. St. Helens 8:32 Sunday morning, May 18, 1980

NYC 9/11

Vertical Structure of the Atmosphere  Temperature varies and rises or falls at different altitudes  Pressure is greater near the surface of the earth  Composition of gases is different at different structural levels in the atmosphere The vertical structure of the atmosphere determines:

Thermal Layers of the Atmosphere  Exosphere  Thermosphere  Mesosphere  Stratosphere  Troposphere

Temperature Variation with Elevation  From sea level through the troposphere temp decreases  At 12 miles it starts to increase  At 30 miles bottom of mesosphere it starts to decrease again  Minimum at 50 miles

Vertical Thickness of Atmosphere  Not a consistent depth/thickness  Over the equator, the troposphere is deepest/thickest  Over the poles, it is shallowest/thinnest N S

Atmospheric Pressure  Can be thought of as the weight of overlying layers of air compressing the lower layers  Atmospheric pressure is highest at sea level and decreases with altitude  As you climb a mountain the atmospheric pressure decreases. We say the air is thinner.

Atmospheric Pressure

Spatial Location of Atmospheric Mass

Atmospheric Composition Good mix = uniform distribution Not mixed = layered

The Ozone Problem  Natural Atmospheric Ozone  Destruction of Ozone by Chlorofluorocarbons (CFCs)  The Antarctic Ozone Hole

Vertical Structure of the Atmosphere Note: the Ozone Layer overlaps the Troposphere – the zone we live in!

Natural Ozone

Ozone Destruction by CFCs

Ozone Depletion

Weather and Climate  Elements of Weather and Climate  Controls of Weather and Climate

Elements & Controls  Temperature  Pressure  Wind  Moisture Content  Latitude  Distribution of land and water  General circulation of the atmosphere  General circulation of the oceans  Elevation  Topographic Barriers  Storms ELEMENTSCONTROLS

Latitude

General Circulation of the Atmosphere Figure 3-14

General Circulation of the Oceans

Elevation

Topographic Barriers

Storms