17.1 The Atmosphere17.1 The Atmosphere

Unit 7: Atmosphere, Weather, and Climate

WeatherWeather – the state of the atmosphere at – the state of the atmosphere at a given time a given time

vs. vs.

ClimateClimate – weather over many years – weather over many years

Most important measurable Most important measurable properties:properties:

1. Temperature1. Temperature2. Humidity2. Humidity3. Type and amount of precipitation3. Type and amount of precipitation4. Air pressure4. Air pressure5. Speed and direction of wind 5. Speed and direction of wind

Composition of atmosphereComposition of atmosphere

A mixture of gases:A mixture of gases:

– Nitrogen 78%Nitrogen 78%– Oxygen 21%Oxygen 21%– Argon less than 1%Argon less than 1%– COCO22 less than 1% less than 1%

– Water vapor varies from 1-4%Water vapor varies from 1-4%

Volume of Clean, Dry AirVolume of Clean, Dry Air

Variable Components / Human Variable Components / Human InfluenceInfluence

Water vapor is the source of all clouds & Water vapor is the source of all clouds & precipitation. Water vapor absorbs heat given precipitation. Water vapor absorbs heat given off by Earth & some solar energy. (Like CO2)off by Earth & some solar energy. (Like CO2)

Ozone (O3)Ozone (O3) Primary pollutants = emitted directly from Primary pollutants = emitted directly from

identifiable sourceidentifiable source Secondary pollutants = not emitted directly Secondary pollutants = not emitted directly

into air.into air.

Primary PollutantsPrimary Pollutants

Structure of the AtmosphereStructure of the Atmosphere

Atmosphere rapidly thins Atmosphere rapidly thins (pressure decreases) as (pressure decreases) as altitude increases (as altitude increases (as you travel away from you travel away from Earth)Earth)

Atmospheric pressure is Atmospheric pressure is the weight of the air the weight of the air above above

Layers of the atmosphere – based Layers of the atmosphere – based on temperature changeson temperature changes

Colder as you climb higherColder as you climb higher Divided into 4 layers based on temperature:Divided into 4 layers based on temperature:

– Troposphere: bottom layer, temp decreases w/ Troposphere: bottom layer, temp decreases w/ increase in altitudeincrease in altitude

– Stratosphere: temp. remains constant to height ~20 Stratosphere: temp. remains constant to height ~20 km then gradually increases (heated…why?)km then gradually increases (heated…why?)

– Mesosphere: temps. decrease w/ height until Mesosphere: temps. decrease w/ height until mesopause.mesopause.

– Thermosphere: contains only tiny amt of the Thermosphere: contains only tiny amt of the atmosphere’s mass. Temps. Increase atmosphere’s mass. Temps. Increase

Earth – Sun RelationshipEarth – Sun Relationship 2 main motions2 main motions

– Rotation: spinning on axisRotation: spinning on axis– Revolution: movement of Earth in its orbit Revolution: movement of Earth in its orbit

around the sunaround the sun Seasonal changes occur bc Earth’s position Seasonal changes occur bc Earth’s position

to the sun constantly changes as it travels to the sun constantly changes as it travels along its orbitalong its orbit

If the axis was NOT tilted we would not have If the axis was NOT tilted we would not have seasonal changesseasonal changes

Axis points to the North StarAxis points to the North Star

Summer Solstice: 1Summer Solstice: 1stst day of summer (NH day of summer (NH leaning toward the sun)leaning toward the sun)

Winter Solstice: 1Winter Solstice: 1stst day of winter (NH leaning day of winter (NH leaning away from the sun)away from the sun)

Autumnal Equinox: Sept. 22 or 23 in NH Autumnal Equinox: Sept. 22 or 23 in NH (occurs halfway btw the solstice)(occurs halfway btw the solstice)

Spring Equinox: March 21 or 22 in NH (axis Spring Equinox: March 21 or 22 in NH (axis neither leaning toward or away from the sun)neither leaning toward or away from the sun)

Length of daylight = Earth’s position in orbit Length of daylight = Earth’s position in orbit – Summer = longer daylightSummer = longer daylight

Review/PreviewReview/Preview

1.1. List the layers and boundaries of List the layers and boundaries of atmosphere in order from bottom to top.atmosphere in order from bottom to top.

2.2. What gas absorbs short wavelength UV What gas absorbs short wavelength UV radiation? What gases absorb long radiation? What gases absorb long wavelength radiation?wavelength radiation?

3.3. Where are the answers to #2 found? (in Where are the answers to #2 found? (in which two atmospheric layers?)which two atmospheric layers?)