The Atmosphere Word Origin from Greek atmos, means “vapor”; and Latin sphaera, means “sphere” The atmosphere is a thin layer of gases surrounding Earth.atmosphere

Contains the oxygen and water necessary for life on Earth. Provides insulation that helps keep temperatures on Earth within a range in which living organisms can survive. Helps protect living organisms from some of the Sun’s harmful rays and meteorites. Importance of Earth’s Atmosphere

Origins of Earth’s Atmosphere Erupting volcanoes emitting hot gases surrounded the planet to form an atmosphere. The ancient atmosphere was thought to be water vapor with a little carbon dioxide and nitrogen, but not enough oxygen to support life.

As Earth and its atmosphere cooled, the water vapor condensed into liquid, rain fell, and then evaporated from Earth’s surface for thousands of years. Eventually water began to accumulate on Earth’s surface, forming oceans. (the Water Cycle began)

Earth’s first organisms could undergo photosynthesis, which changed the atmosphere. They removed CO 2 from the atmosphere and released oxygen into it. Eventually the levels of CO 2 and oxygen supported the development of other organisms.

Composition of the Atmosphere Amounts of water vapor, carbon dioxide, & ozone vary.

What Else is in the atmosphere? Many tiny solid particles: pollen, dust, salt, ash from volcanic eruptions, and exhaust soot from cars and industry. Most common liquids: water vapor and acids

Layers of the Atmosphere Air we breathe & Weather - airplanes here Has Ozone Layer - protects us from Sun’s harmful radiation – high altitude balloons can be here Combined, contains only 1% of atmospheric gases – Meteors usually burn up here Ions from Sun here reflect AM radio waves. Ions also hit air molecules, causing auroras – Northern Lights So few gas molecules here that Sun’s energy sends them shooting into space Gravity = force pulling the molecules in the atmosphere toward Earth, so there are more of them closer to Earth

Air Pressure and Altitude Air Pressure = the amount of force that a column of air exerts on anything below it Less Air Pressure More Air Pressure Gravity = the force pulling air down

So why doesn’t it crush you? Earth's atmosphere is pressing against each square inch of you with a force of 1 kg per sq. cm. (14.7 lbs. per sq. in)! The force on 1,000 sq. cm. (a little larger than a sq. ft.) is about a ton! How much pressure are you under? Because you have air inside of you too. That pushes back. So there is a balance of pressures!

A Barometer measures air pressure – uses a vacuum inside How do we measure air pressure? 1 atm =Old Way mb = (millibars) in.

Temperature and Altitude of the Troposphere

Space Shuttle Re-entry from Space Orange layer is the Troposphere, white is the Statosphere, and blue is the Mesosphere

Energy from the Sun Energy is transferred by conduction, convection, and radiation.

Radiation = transfer of energy by electromagnetic waves 90% of sun’s radiation reaching Earth is a combination of visible, infrared, and ultraviolet radiation (mostly visible) Electromagnetic Radiation / Spectrum

As Sun’s radiation passes through the atmosphere, some of it is absorbed and some of it is reflected back into space.

Absorb Reflect Gases - CO 2, O 2, 0 3 (ozone) Clouds Particles – dust, pollen, etc. Particles – dust, pollen, etc. Water Vapor Bright Surface Oceans Oceans Earth’s Surface Earth’s Surfaces Only IR & UV radiation is absorbed. Visible light is not absorbed. End Result: Earth’s surface only absorbs about 50% of incoming solar radiation.

The UV rays are harmful to skin. Most of the visible light gets converted to heat (IR). The IR rays are detected as thermal (heat) energy. Sun’s energy that is absorbed by Earth gets radiated back as IR energy.

Radiation Balance The amount of incoming radiation is the same as the amount of outgoing radiation. This radiation balance maintains an overall temperature range on Earth that supports life.

Problem! Greenhouse Gases Create a Heat Surplus! The gases that trap IR best are water vapor, carbon dioxide, and methane. They act like the walls of a greenhouse. Raises the average temperature on Earth Global Warming

Energy Transfer Energy is transferred by conduction, convection, and radiation.

Conduction = Occurs where the atmosphere touches Earth. the transfer of thermal energy by collisions between particles of matter – needs touching

Convection = Transfer of thermal energy by the movement of matter from one place to another

Convection air currents - becomes denser & sinks - becomes less dense

Remember - Convection currents in the mantle causes plate movement

Convection in the oceans causes currents

Water as a Heat Exchanger Over 70% of Earth is covered by water! Water releases or absorbs heat energy during phase changes. This heat is exchanged with the atmosphere. Water holds heat longer and releases it slower than land.

High Temp.Low Temp.

Air is constantly moving and circulating. Warm, less dense air has less pressure. It rises. Cool, denser air has more pressure. It sinks and goes under the warm air, pushing the warm air upward. Warm Air Cold Air

Occassionally, warm air gets trapped by some colder air above it – temperature inversion This is a problem if it lasts a few days because it also traps pollution and any particles, such as pollen and dust.

Globally, Earth is heated by the sun unevenly.

Cold air is denser & has higher pressure – So it sinks. Warm air is less dense & has lower pressure – So it rises. Wind = movement of air from areas of high pressure to areas of low pressure

Coriolis Effect – because the Earth is spinning, the winds appear to curve – causes global wind patterns Global Wind Belts Polar Easterlies – blow from east to west – at 60 ° N & 60 ° S to poles Prevailing Westerlies – blow from west to east – at 30° – 60 ° N & S latitudes Trade Winds – blow from east to west – at Equator to 30 °N and 30 °S

Local Winds - due to local temperature and pressure differences Sea Breeze – Wind blows from the sea to the land. Why? During the day, the land heats up faster than the water. So the air above it is warmer than the air above the water. The hot air over the land rises (has less pressure), and the cooler air above the sea (has more pressure) moves in to take its place.

Land Breeze – Wind blows from the land to the sea. Why? At night, the land cools down (loses heat) faster than the water. So the air above it is cooler than the air above the water. This cooler air sinks and moves toward the sea to take the warmer air’s place.