The Atmosphere

THE AIR AROUND YOU Weather – condition of the atmosphere at a particular time and place Atmosphere – the mixture of gases that surrounds our planet

THE AIR AROUND YOU Composition of the Atmosphere 78% Nitrogen 21% Oxygen 1% Water Vapor, Carbon Dioxide, and Other Gases

THE AIR AROUND YOU Importance of Earth’s Atmosphere The atmosphere contains oxygen and other gases that living things need to survive.

THE AIR AROUND YOU Importance of Earth’s Atmosphere The atmosphere traps energy from the sun which keeps the Earth’s surface warm enough for water to exist as a liquid.

The atmosphere protects living things from dangerous radiation. THE AIR AROUND YOU Importance of Earth’s Atmosphere The atmosphere protects living things from dangerous radiation. ultraviolet radiation

THE AIR AROUND YOU Importance of Earth’s Atmosphere The atmosphere prevents most meteoroids from hitting Earth’s surface.

PROPERTIES of AIR The air consists of atoms and molecules, which have mass, so air has mass. Gravity pulls the gas molecules toward Earth’s surface giving them weight. The amount of mass in a given volume of air is its density. If there are more molecules in a given volume, the density is greater. More Dense Less Dense Air pressure – the result of the weight of a column of air pushing down on an area The atmosphere is heavy! The weight of the column of air above your desk is the same weight as a large school bus!

Layers of the Atmosphere Air temperature changes as you increase in altitude. Some parts of the atmosphere are “warmer” because they contain gases that absorb solar energy. Other parts do not have these gases and are “cooler” as a result. Scientists divide Earth’s atmosphere into four main layers according to changes in temperature. These four layers are troposphere, stratosphere, mesosphere, and thermosphere.

Layers of the Atmosphere TROPOSPHERE The inner, or lowest layer of the atmosphere The densest layer of the atmosphere (has the most “stuff”) Almost all of Earth’s weather occurs here (and ALL life) As altitude increases, the temperature decreases

Layers of the Atmosphere STRATOSPHERE The layer that extends from the top of the troposphere Very thin air that contains little moisture (lower stratosphere is “COLD”) Contains the ozone layer which absorbs energy from the Sun Ozone absorbs the Sun’s energy which is converted to heat and warms the air The ozone layer protects living things from dangerous ultraviolet radiation from the Sun As altitude increases, the temperature increases

Layers of the Atmosphere MESOSPHERE The layer above the stratosphere Protects Earth’s surface from being hit by most meteoroids Temperature decreases as altitude increases *(“COLDEST” layer; has lowest temperatures)

Layers of the Atmosphere THERMOSPHERE The outermost layer of the atmosphere This layer gradually blends with outer space Even though the temperature is VERY high, it is not “hot”

Layers of the Atmosphere THERMOSPHERE The thermosphere is divided into two layers: The lower layer is called the ionosphere Molecules here become electrically charged = ions Brilliant light displays occur here (Northern Lights) The outer layer of the thermosphere is the exosphere Phone calls and television pictures come from the communication satellites here

Layers of the Atmosphere The OZONE Layer A layer of gas made of ozone is found in the stratosphere. Ozone is a form of oxygen and it absorbs ultraviolet radiation. Layers of the Atmosphere The OZONE Layer

There is a hole in the ozone layer. It is argued whether or not the condition of the ozone layer has improved since the ban of CFCs. The United Nations has predicted that the ozone will return to its pre-1980s condition by the year 2050.

Scientists think that chlorofluorocarbons or CFCs caused the ozone layer to thin. These chemicals were once used in aerosol sprays, refrigerants, and air conditioners. CFCs are now banned in the many countries.

The Greenhouse Effect and Global Warming The carbon dioxide in Earth’s atmosphere traps heat. This is called the Greenhouse Effect. Many scientists believe that an increase in carbon dioxide means an increase in temperature. The average temperatures around the world are increasing; we call this trend global warming.

There are several possible sources for this increase in carbon dioxide: Automobiles Factories Deforestation: when large amounts of trees are cut down

Remember that the Greenhouse Effect is GOOD Remember that the Greenhouse Effect is GOOD! Human activities are believed to be altering the amount of carbon dioxide in our air.

The Greenhouse Effect and Global Warming

ACID RAIN Burning fossil fuels releases chemicals into the air. These chemicals combine with water droplets in the atmosphere which forms sulfuric acid and nitric acid. Acid precipitation falls, harming aquatic life and plants (especially pine trees). ACID RAIN

Pollutants are harmful substances in the air, water, or soil. Air pollution can affect the health of humans and other living things. Using Figure 12, list six effects of air pollution on human health. Natural processes can add particles to the atmosphere – list five examples. AIR QUALITY 1. Dizziness 4. Cough 2. Headaches 5. Lung diseases 3. Allergies 6. Eye/Nose/Throat Irritation Forest fires Soil Erosion Dust storms Wind carries pollen/mold Erupting volcanoes

AIR QUALITY Human activities can also add particles to the atmosphere – list three examples. State at least three pollutants produced by burning fossil fuels. 1. Farming 2. Construction 3. Burning fossil fuels 1. Carbon Monoxide 2. Nitrogen Oxide 3. Sulfur Oxide

The term smog was created by combining the words smoke and fog. Typically, London-type smog forms when particles in coal smoke combine with water droplets in humid air. London air is MUCH cleaner than it was 100 years ago. AIR QUALITY

AIR QUALITY The brown haze that develops in sunny cities is called photochemical smog. The action of sunlight on pollutants form a brownish mixture of ozone and other pollutants. The Environmental Protection Agency (EPA) monitors air pollutants in the United States to ensure air quality.