Composition of the Atmosphere • The atmosphere mostly consists of nitrogen (78%), oxygen (21%), and argon. 99% composed of Nitrogen and Oxygen Remaining 1% made up of small amounts of other gases
Structure of the Atmosphere • Atmosphere composed of several layers
Troposphere • Closest to Earth • Altitude 0-10 km • Contains most of the mass of the atmosphere • Weather occurs here, pollution collects • Upper limit called tropopause • Tropopause is where gradual decrease in temperature stops
Stratosphere -Above troposphere -Altitude 10-50 km -Contains mostly ozone -Ozone absorbs more UV radiation, so this layer is heated -Upper limit called stratopause -Stratopause is where gradual increase in temperature stops
Mesosphere • Above stratosphere • Altitude 50-80 km • No concentrated ozone here, so temperature drops again • Upper limit called mesopause • Mesopause is where gradual decrease in temperature stops
Thermosphere • Above mesosphere • Altitude 80 km and above until outermost boundary of atmosphere • Contains a small part of the atmosphere’s mass • Little air that is in this layer increases in temperature again to greater than 1000C
The Ionosphere • The thermosphere can be identified in two parts- the ionosphere and the exosphere. • Ionosphere: 80 km-640 (about 400 miles = 640 km). • It contains many ions and free electrons (plasma). • Auroras occur in the ionosphere.
Exosphere • Outermost layer of Earth’s atmosphere • Light gases like helium and hydrogen found here • Above exosphere is outer space • No clear boundary between atmosphere and space
Atmosphere Energy • The Sun is the source for all energy in the atmosphere. • Three ways the energy transfer occurs: • Radiation • Conduction • Convection • Flash Animation
Radiation • Radiation is the transfer of energy through space by visible light, UV radiation, and other forms of electromagnetic waves
Conduction • Conduction is the transfer of heat energy that occurs when particles collide • Through conduction, Earth’s surface transfers energy to nearby air particles in troposphere. • Conduction only affects small layer of atmosphere.
Convection • Convection is the transfer of heat energy by the flow of a heated substance • Pockets of air near Earth’s surface are heated, become less dense and rise • As warm air rises, it expands and starts to cool. As it cools, its density increases and the cooler air sinks. As it sinks, it warms again and process starts over.
Temperature and Heat • Temperature-measurement of energy of a substance; interprets atmospheric processes. • Heat-transfer of energy from two objects of different temperatures; fuels atmospheric processes.
Pressure and Density • Air pressure increases towards Earth’s surface because of the greater mass of the atmosphere above you. • Atmospheric pressure decreases with height because there are fewer gas particles above you. • Density is proportional to amount of particles.
Wind • Air moves in response to density imbalances created by the unequal heating and cooling of Earth’s surface. • These imbalances, in turn, create areas of high and low pressure. • Wind can be thought of as air moving from an area of high pressure to an area of low pressure.
Humidity • Humidity-amount of water vapor in air. • Relative humidity-ratio of water that air contains and the maximum amount of water the air could contain. • Warm air is more capable of holding more moisture that cold air. • Do we usually ever complain of humidity in winter?
Clouds • Dew point-temperature at which air must be cooled to reach saturation. • Condensation-phase change from gas to liquid; only occurs at saturation. • Lifted Condensation Level-LCL; point at which condensation occurs.
Cloud Formation • Air masses of different temperatures collide. • The less dense, warmer air mass rises over the more dense, colder air mass. • As the warm air rises, it cools, and once it reaches the LCL, water vapor will condense around condensation nuclei to become a cloud, if the density of condensation nuclei is great enough. • Condensation nuclei-particles in the air around which cloud droplets can form.
Precipitiation • Coalescence-occurs when cloud droplets collide and join together to form a larger droplet. • When the droplet becomes too heavy to be held aloft, gravity takes over and it falls to Earth as precipitation.
Another Method of Cloud Formation Orographic Lifting-air mass is forced to lift due to topography, cooling down quickly in the process, causing condensation and cloud formation.
Meteorology • Weather-current state of the atmosphere. • Climate- describes the average weather over a long period of time
Air Masses • A large body of air with similar • TEMPERATURE • HUMIDITY
Air Masses’ Characteristics • Source Regions Air Mass Air Mass Over water: more moist. Over land: drier.
Types of Air Masses DESCRIPTIONCONDITIONLOCATION FORMED • Maritime: (m) moist (marina/water) • Continental:(c) dry (continents/land) • Tropical:(T) warm (tropics) • Polar:(P) cold (poles)
Types of Air Masses • If we combinea temperatureand humiditycharacteristicwe can make • 4 differenttypes of air • masses.
Types of Air Masses cPContinental Polar mPMaritime Polar Dry, cold air to centraland eastern US. Moist, cold air to east areas of Canada mPMaritime Polar Moist, cold air to west coast of the US. mTMaritime Tropical mTMaritime Tropical Moist, warm air to west coast of the Mexico. cTContinental Tropical Moist, warm air to southeast coast of the US. Dry, warm to Desert SW Mr. Fetch's Earth Science Class Mr. Fetch’s Earth Science Classroom
Air Mass Modification mPMaritime Polar Moist, cold air to west coast of the US. Air masses move to be prevailing winds.The winds cause the air masses to move over land and water.As the air masses move, they change.This is called air mass modification. The air masses becomes more like thearea it is moving over… ….. And At the same time, the area the air massis moving over becomes more like themass. Mr. Fetch’s Earth Science Classroom
Weather Systems • CoriolisEffect-caused by Earth’s rotation; causes moving objects to deflect right in N. hemisphere, left in S. hemisphere. • This effect creates a global wind system that transports air masses.
Three Types of Wind Systems • Trade winds • Prevailing westerlies • Polar easterlies
Trade winds • Move between equator and 30° N and S latitude. • Air sinks, warms, and returns to equator in westerly direction.
Prevailing Westerlies • Occurs between 30° and 60° latitude • Moves in opposite direction of trade winds • Moves weather across U.S.
Polar Easterlies • Occur between 60° and poles • Cold air
Fronts A boundary between two air masses: Occluded fronts
mPMaritime Polar Moist, cold air to west coast of the US. mTMaritime Tropical Moist, warm air to southeast coast of the US. When air masses meet… Mr. Fetch's Earth Science Class Mr. Fetch’s Earth Science Classroom
Cold Fronts - When cold air hits warm air.- Warm air is forced violently up.- Rising air creates clouds, rain, and storms. (FRONTAL LIFTING) Steep Slope Mr. Fetch’s Earth Science Classroom
Cold Fronts • When cold air hits warm air.- Warm air is forced violently up.- Rising air creates clouds, rain, and storms. (FRONTAL LIFTING) • Flash Animation
Cold Fronts “COLD FRONT” … umm its gets colder , duh!
Warm Fronts - When warm hits cold air.- Warm air gently glides up over the cold air.- Rising air creates clouds and showers. (Less Violent). Gentle Slope Mr. Fetch’s Earth Science Classroom
Warm Fronts “WARM FRONT”… right, it gets warmer, good.
Stationary Front - When a warm or cold front stops moving.- Usually several days of clouds and showers.
Occluded Front • Occluded front occurs when cold front wraps around warm front.
SYSTEM TYPES LOW PRESSURE: cyclones • form along fronts.(Unstable) • rising air. • winds rotate counter-clockwise around low pressure systems. • Rainy, stormy weather L Mr. Fetch's Earth Science Class
The high’s and low’s of weather… HIGH PRESSURE: anticyclones • sinking air. (Stable) • The sinking air stops clouds from forming. • winds rotate clockwise around high pressure systems. • Sunny, clear weather H Mr. Fetch's Earth Science Class