The Atmosphere Earth’s Atmosphere and Distribution of Earth’s Heat on Land and Water
EQ: How do air pressure and temperature vary in the atmosphere? Standards S6E3b; S6E4a,b; S6E5j; S6E6a
The Air Around You Atmosphere Chapter 12 Section One
The Air Around You • Weather is the condition of Earth’s atmosphere at a particular time. • Atmosphere: the layer of gases that surrounds Earth • Earth’s atmosphere is composed of nitrogen, oxygen, carbon dioxide, water vapor, and other gases. • Earth’s atmosphere contains oxygen and other gases that living things need to survive.
Composition of the Atmosphere • Nitrogen • Makes up ¾ of the air we breathe. • Oxygen • 2nd most abundant gas in the atmosphere • Plant and animals take oxygen from their surroundings and use it to release energy from food in a cellular process. • Is needed for fire to burn • Ozone • Form of oxygen that has three oxygen atoms in each molecule
Composition of the Atmosphere • Carbon dioxide • Is present in small amounts in the atmosphere • Essential to life • Animals produce carbon dioxide • Burning fossil fuels increases the amount of carbon dioxide in the atmosphere. • Water Vapor • Water in the form of a gas • Produces clouds
Importance of the Atmosphere • Earth’s atmosphere makes conditions on Earth suitable for living things. • Traps energy from the sun which keeps most of the Earth’s surface warm. • Water exist in liquid form.
Air Pressure Chapter 12 Section Two
Air Pressure • Properties of air: • Consists of atoms and molecules that have mass • Mass • Density • Pressure • Pressure is the force pushing on an area or surface. • Air pressure is the result of the weight of a column of air pushing down on an area.
Air Pressure • How are mass and air pressure related? • The weight of air in the atmosphere causes air pressure. • So why doesn’t air pressure crush objects? • The reason is that the molecules of air push in all directions. The air pushing down on an object is balanced by the air pushing up on the object. • How does the density of air affect air pressure? • Denser air exerts more pressure than less dense air.
Measuring Air Pressure • An instrument used to measure air pressure is a barometer. • Two kinds of barometers • Aneroid • Mercury • Unit of Air Pressure • 2 different units of measurement • Inches of mercury • millibars
How does altitude affect air pressure? • Altitude, or elevation, is the distance above seal level. • Air pressure decreases as altitude increases. • Less oxygen molecules to breathe at higher altitudes. • As air pressure decreases, so does density.
Altitude Affects Air Pressure • Sea level air has the weight of the whole atmosphere pressing on it. • So air pressure is greater at sea level. • The air near the top of the atmosphere has less weight pressing on it , and thus has lower air pressure.
Altitude Also Affects Density • As you go through the atmosphere, the density of the air decreases. • This means the gas molecules that make up the atmosphere are farther apart at high altitudes than they are at sea level. • The air contains 21% oxygen. • There are fewer oxygen molecules at high altitudes.
Layers of the Atmosphere • Key Concepts • What are the four main layers of the atmosphere? • What are the characteristics of each layer?
What are the layers of the atmosphere? • Scientists divide Earth’s atmosphere into four main layers classified according to changes in temperature. • Troposphere • Stratosphere (Ozone layer) • Mesosphere • Thermosphere • Ionosphere • Exosphere
Troposphere • We live in the troposphere. • All weather and water vapor are in this layer. • Gets colder as you go up. • Clouds • 0-18 km
Stratosphere • 2nd layer of the atmosphere • Temperature s get warmer are you go up. • 12 – 50 km • Contains the Ozone layer. • Absorbs ultraviolet radiation
Mesosphere • Protects Earth’s surface from being hit by meteoroids. • Coldest region of atmosphere • 50 – 80 km
Thermosphere • Outermost layer of Earth’s atmosphere • Above 80 km • Air is thin, it is very hot because the sun strikes this layer first • Divided into 2 layers: • Ionosphere, lower layer of thermosphere • 80 – 400 km • Radio waves bounce back to Earth’s surface • Exosphere, outer layer of thermosphere • 400 – 1000 km • Artificial satellites orbit here
Energy from the Sun • Kinds of energy from the sun • Visible light • Infrared radiation • Ultraviolet radiation • Can cause sunburns, skin cancer, and eye damage • When Earth’s surface is heated, it radiates most of the energy back into the atmosphere as infrared radiation. • Greenhouse effect • Process by which a blanket of gases around the Earth that hold heat in the atmosphere.
Heat Transfer • Three forms of heat transfer: • Radiation • Direct transfer of energy by electromagnetic waves • Ex. – heat from the sun travels by radiation • Conduction • Direct transfer of heat from one substance to another substance by direct contact. • Ex. – pot on a stove • Convection • The transfer of heat by the movement of fluid • Ex. – Upward movement of warm air and the downward movement of cool air form convection currents.
Winds • A wind is the horizontal movement of air from an area of high pressure to an area of low pressure. • Winds are • Caused by the unequal heating of the earth. • Cool, dense air flows under warm, less dense air. • Measuring wind • Speed (anemometer) • Direction (wind vane) • Wind-chill factor – the increased cooling a wind can cause.
Local Winds • Winds that blow over short distances. • Caused by the unequal heating of Earth’s surface within a small area. • During the day, land warms up faster than water. • At night, the land cools faster than water.
Local Winds • Sea Breeze • Local wind that blows from an ocean or lake.
Local Winds • Land Breeze • The flow of air from land to a body of water.
Global Winds • Winds that blow steadily from specific directions over long distances • Created by unequal heating of Earth’s surface. • Occur over a large area • Global convection currents • Produced by temperature differences between the equator and the poles • Coriolis Effect • Earth’s rotation makes winds curve
Global Wind Belts • Major wind belts • Trade winds • Polar easterlies • Prevailing westerlies
Atmosphere Review • Can you answer the following questions: • What are the main gases in the atmosphere? • Name the 6 layers of the atmosphere? • What are 3 forms of heat transfer? • What causes wind? • What are the major global winds?