Chapter 3: The Atmosphere 3.1 The Air Around You

The Atmosphere A whole layer of air that surrounds Earth Supports and protects life Keeps Earth warm Very thin

The Atmosphere Mostly made of gases. Nitrogen (N) – 78% Oxygen gas (O) – 21% Argon, CO2, other gases – 1% Some small liquid and solid particles Dust, sea salt, water droplets

The Atmosphere Nitrogen promotes plant growth and is in all living things. Oxygen is needed for animals to breathe, energy for living things, and combustion. CO2 is used to make food for plants.

Water Vapor Air contains water vapor – water in the form of a gas. Plays an important role in the weather Clouds are made of water vapor that condenses into droplets

Particles Air contains solid and liquid particles, such as smoke, ash, dust, salt, and chemicals.

Atmosphere as a System Events in one part of the atmosphere affect other parts of the atmosphere, as well as other parts of Earth’s system. Wind and the ocean Ocean currents and the climate Storms

Chapter 3: The Atmosphere 3.2 Air Pressure

Density and Pressure Density: the amount of mass in a given volume The more closely the particles are packed together, the more dense the object is. Air pressure: the force of air pushing on an object; goes in all directions.

Measuring Air Pressure Barometer: instrument used to measure air pressure. Measured in units - bars Mercury barometer: liquid mercury is moved due to pressure changes; when there is more pressure, it goes higher in the tube.

Measuring Air Pressure Aneroid barometer: pressure causes the instrument to change shape slightly, leading to a needle moving inside of it.

Altitude Altitude: elevation or distance above sea level

Altitude and Pressure Sea-level air has the weight of the whole atmosphere pressing on it. As you go higher into the atmosphere, there is less pressure pushing down. As altitude increases, pressure decreases.

Altitude and Density The particles in the air begin to spread further apart when you go higher in the atmosphere. As altitude increases, density decreases.

Chapter 3: The Atmosphere 3.3 Layers of the Atmosphere

The Layers of the Atmosphere The transfer of heat energy changes in the different layers of the atmosphere. Troposphere Stratosphere Mesosphere Thermosphere

Troposphere The layer nearest Earth’s surface Contains about 80% of the mass in the atmosphere and almost all of the water vapor Warmest at ground level and goes down about 6.5 degrees C every kilometer.

Stratosphere A clear, dry layer Contains gas we call ozone. This absorbs a type of solar radiation that is harmful to life. The radiation raises the temp of the air, and the temp rises the higher you go into the stratosphere.

Mesosphere The air is extremely thin here. Contains less than 0.1% of the atmosphere’s mass. Meteors burn in this layer. The air here is heated from below, so the further you rise, the cooler it gets.

Thermosphere Starts about 90 km/56 mi above Earth’s surface It gets less dense as altitude increases, but the temperature goes up. The air high in this layer (closest to outer space) gets very hot from solar radiation

Chapter 3: The Atmosphere 3.4 Energy in the Atmosphere

Electromagnetic Waves Energy from the sun travels in Electromagnetic Waves, or EM waves. Most of it is in the form of Visible Light, Infrared Waves, and Ultraviolet waves.

Visible Light Visible light = ROYGBIV Red has the longest wavelength; Violet has the shortest.

Nonvisible Radiation Infrared – not visible by humans, but can be felt as heat. Longer wavelengths than red light Ultraviolet – also is invisible, but can cause skin damage and sunburns to humans. Shorter wavelengths than violet light

Energy in the Atmosphere Some of the energy is reflected or absorbed by the atmosphere; the rest reaches the surface. Some UV radiation is absorbed in the ozone layer (stratosphere); most IR radiation comes closer to Earth’s surface and gets absorbed by water vapor and CO2.

Energy in the Atmosphere About 50% of the sun’s energy reaches Earth’s surface as heat, and some of that is sent back into the atmosphere as IR radiation. Gases called greenhouse gases keep heat in Earth’s atmosphere, close to the surface – called the greenhouse effect. Human activity is changing the balance of this natural process, adding more greenhouse gases into the atmosphere.