Things we need to talk about:

•Astro Test

•When you can retake (By May 1!)

•Grades

•Tuesday

4/23/2012

Chapter 11

Atmosphere

•Air is a combination of many gases• 78% nitrogen • 21% oxygen• 1 % argon, hydrogen, carbon dioxide, water vapor, and other gases• The amount of water vapor varies with the seasons, altitude, and location•What locations would have more water vapor?• Less?

Atmosphere composition

•Ozone – a gas formed by the addition of a third oxygen atom to an oxygen molecule (O2)

• Exists in small quantities in a layer above Earth’s surface•Absorbs UV radiation from the Sun

Ozone

•Atmosphere is composed of layers

•Each layer differs in composition and temperature

Structure of the Atmosphere

•Troposphere – The layer closest to the Earth•Contains most of the mass of the atmosphere•Contains water vapor•Most of the weather takes place here•Collects air pollution•Characterized by decrease in temperature from bottom to top

Layers of the Atmosphere

•Stratosphere – layer above the troposphere•Made primarily of concentrated ozone•Absorbs more UV radiation than the troposphere•Air gradually increases in temperature to the top of the layer

Layers of the Atmosphere

•Mesosphere – Layer above the stratosphere•No concentrated ozone• Temperature decrease• Thermosphere – Layer above the mesosphere•Contains only a small portion of the atmosphere’s mass• Temperature increases again (up to 1000*C)•Molecules are so sparse that it would not seem warm

Layers of the Atmosphere

•Exosphere – The outermost layer•No clear boundary between atmosphere and space

Layers of the Atmosphere

•Radiation – the transfer of energy through space by visible light, UV radiation, or other forms of electromagnetic waves• Earth is continuously absorbing solar radiation• It is also continuously sending it back into space• 6% of solar rays are reflected by the atmosphere• 25% is reflected by the clouds• 4% is reflected by the Earth’s surface• 15% is absorbed by the atmosphere• 50% directly or indirectly absorbed by Earth’s surface• The rate of absorption depends on the physical characteristics of the area and the amount of solar radiation it receives.

Solar fundamentals

•Solar radiation does not heat the air directly• So how does the air become warm?•Much of the solar radiation passes through the atmosphere and is absorbed by the Earth’s surface• The surface then radiates energy

Solar Fundamentals

•Conduction – The transfer of energy that occurs when molecules collide•Affects only a very thin atmospheric layer near Earth’s surface• Energy is transferred from the particles of air near Earth’s surface to the particles of air in the lowest layer of the atmosphere

Solar Fundamentals

•Convection – the transfer of energy by the flow of a heated substance• Pockets of air near the Earth’s surface are heated, become less dense that the surrounding air, and rise• Once it rises, it expands and starts to cool• Then it sinks and warms again

Solar Fundamentals

Words you should probably know…

Atmosphere Vocab…

• Temperature – a measurement of how rapidly or slowly molecules move around• More molecules in a given space generate a

higher temperature• Measured in degrees Fahrenheit (°F), degrees

Celsius (°C), or Kelvin

• Heat – the transfer of energy that occurs because of a difference in temperature between substances• Heat always flows from an object of higher

temperature to an object of lower temperature

Temperature vs. Heat

•Dew Point – the temperature to which air must be cooled at constant pressure to reach saturatuion• Saturation – the point at which the air holds as much water vapor as it possible can•Why is this important?• Until air is saturated, condensation cannot occur• Condensation – occurs when matter changes from a gas to a liquid

Other Atmospheric Measurements

•Air Pressure – the gravitational attraction between Earth and atmospheric gases• Decreases with height because there are fewer particles exerting pressure

Air Pressure

•Wind – air moving from an area of high pressure to an area of low pressure• Changes with height of atmosphere

Wind

•Humidity – the amount of water vapor in the air

•Relative humidity – the ratio of water vapor in a volume of air relative to how much water vapor that volume of air is capable of holding• Relative humidity varies with temperature•Warm air can hold more moisture than cool air• Expressed as a percentage• Problem solving lab p. 283

Humidity

Clouds

Height Shape

Prefix

Description Prefix Description

Cirro High clouds with bases starting above 6000 meters

Cirrus Latin meaning: “Hair”Wispy, stringy clouds

Alto Middle clouds with bases between 2000 m and 6000 m

Cumulus

Latin meaning: “pile or heap”Puffy, lumpy-looking clouds

Stratus Latin meaning: “layer”Featureless sheets of clouds

Strato

Low clouds below 2000 m

Nimbus Latin meaning: “cloud”Low, gray rain clouds

Cloud Classification

Types of Clouds

• Stratus Clouds – form when fog lifts away, covering much of all of the sky in a given area

• Cumulus – puffy, heap; can lead to moisture, thunderstorms, etc.

• Stratocumulus – layer of cloud clumps with thick and thin areas; found ahead or behind frontal systems

• Nimbostratus – generally thick, dense stratus or stratocumulus clouds producing steady rain or snow.

Low Clouds

Types of Clouds

• Altostratus – flat and uniform texture; frequently indicate the approach of a warm front• Do not produce significant precipitation

• Altocumulus – heap-like clouds; may align in rows or streets of clouds

Middle Clouds

Types of Clouds

• Cirrus – wispy, feathery; composed of ice crystals; first sign of an approaching warm front

• Cirrostratus – widespread, veil-like layer

• Cirrocumulus – layered, lumpy clouds; may line up in rows or streets of clouds

High Clouds

Types of Clouds

• Cumulonimbus – puffy walls of clouds associated with thunderstorms

• Fog – layer of stratus clouds on or near the ground

Other Clouds

http://www.crh.noaa.gov/lmk/?n=cloud_classification

Cloud Classification Chart

• Precipitation – all forms of water that fall from clouds

Precipitation

Water CycleEvaporation – the process of changing from a liquid to a gas

Collection – Water soaking into the ground, entering lakes, streams, oceans, falling into bodies of water

Condensation – changing from a gas to a liquid

Precipitation – any form of water coming from the clouds