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Unit 4.2: Atmospheric Composition and Weather. I.4 Atmospheric Layers: A.Troposphere: tropos- = change, turning 1.Where air turns over, is mixed; most.

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Presentation on theme: "Unit 4.2: Atmospheric Composition and Weather. I.4 Atmospheric Layers: A.Troposphere: tropos- = change, turning 1.Where air turns over, is mixed; most."— Presentation transcript:

1 Unit 4.2: Atmospheric Composition and Weather

2 I.4 Atmospheric Layers: A.Troposphere: tropos- = change, turning 1.Where air turns over, is mixed; most weather occurs here 2.Temperatures as altitude b/c air molecules are farther apart, less able to conduct heat 3.Contains 80% of atmospheres mass 4.Tropopause: boundary between troposphere and stratrosphere; varies with location and season: a.Thicker in the tropics, thinner at the poles b/c of air temperature b.Thicker in summer, thinner in winter b/c of air temperature 2

3 B. Stratosphere: strato- = layered 1.Temps as altitude, why? 2.Ozone layer (O 3 ) in stratosphere absorbs UV radiation from the Sun – causes in temperature in this layer. a.Ozone layer protects living organisms from UV damage b.But chlorofluorocarbons (CFCs) react with ozone, create hole in ozone layer 3

4 C.Mesosphere: meso- = middle 1.Temps as altitude 2.Meteors burn up in this layer D.Thermosphere: thermo- = heat 1.Temps b/c atoms absorb high energy radiation, but b/c atoms are so far apart, does not feel hot! 2.Also in this layer: Auroras, space station (ISS) 4

5 II.Composition of the Atmosphere: A.Major components: 1.Nitrogen gas (N 2 ): ~78% 2.Oxygen gas (O 2 ): ~21% 3.Argon gas (Ar): >1% 4.**Carbon dioxide (CO 2 ): 0.036% a.Absorbs heat radiated from Earth to heat atmosphere 5

6 B.Variable components: 1.Water vapor (H 2 O) a.Absorbs Earths heat and solar energy b.When water changes state, it absorbs or releases heat latent heat 2.Aerosols a.Microscopic particles: sea salts, fine soil, smoke/soot, pollen b.Provide seed to form clouds c.Can reflect/absorb solar radiation d.Partly responsible for red- orange sunset 6

7 3.Ozone: O 3 a.O 2 split by UV, single O combines with O 2 to form O 3 (O 2 + O O 3 ) b.Absorbs harmful UV, protects Earths surface c.Concentrated in stratosphere, not evenly 1)Ozone fluctuates based on seasons: summer = more radiation, so more ozone, but air currents move it to poles d.Ozone hole - loss of ozone due to chlorofluorocarbon (CFC) pollution 1)CFCs break down O 3, lose protective layerCFCs break down O 3 2)CFCs from Styrofoam, hairspray propellants, refrigerant for air conditioners 7

8 C.CO 2 and the Greenhouse effect:Greenhouse effect 1.Solar radiation is high energy (UV, visible), passes through atmosphere easily, including greenhouse gases in atmosphere. a.Greenhouse gases: H 2 O, CO 2, methane 2.Earth absorbs, re-radiates infrared (IR) into atmosphere, but IR has less energy than incoming solar radiation. 3.Greenhouse gases absorb IR, reflect it back to Earths surface instead of allowing it to escape into space. 4.More gases = more IR absorption = higher temps. overall 8

9 D.Human activities that increase levels of GG: 1.Burning coal/oil releases CO 2 2.Deforestation – why? Trees capture CO 2 in photosynthesis If fewer trees, then more CO 2 into atmosphere 3.Livestock management more methane 9

10 E.Atmospheres of Nearby Planets: 1.Venus: density of atmosphere is 93 times that of Earth a.CO 2 = ~95%, N 2 =~4% b.Density and amount of CO 2 = high temps on surface: ~467°C c.Venus has a runaway greenhouse effect b/c of dense CO 2 2.Mars: density of atmosphere is <1% of Earths atmosphere a.CO 2 = ~95%, N 2 = ~2.7%; Ar = ~1.6% b.Mostly CO 2, but so rarefied, no greenhouse effect 1)Rarefied: less dense, spread out Composition of Venus atmosphere 10

11 III. Weather vs. Climate A.Weather: 1.State of the atmosphere at a given place and time 2.Constantly changing B.Climate: 1.All weather that describes a particular place, region C.Both depend on 6 basic elements: 1.Air temperature 2.Humidity 3.Cloudiness – type and amount 4.Precipitation – type and amount 5.Air pressure 6.Speed and direction of wind 11

12 D. 6 Factors that Affect Temperature 1.Latitude: closer to equator = higher temps a.More direct rays, less atmospheric interference 2.Elevation/Altitude: a.Higher elevations are cooler b/c further away from heat generated at Earths surface b.Atmosphere is less dense (air is farther apart) as you rise in altitude so less heat is transferred 12

13 3.Differential heating of land/ water: a.Land surfaces are solid, absorb radiation at surface b.Water is transparent, can absorb more radiation below surface 1)Heated water mixes, redistributes heat, so more stable 2)Specific Heat: capacity to store thermal energy Water has high specific heat; Land has lower specific heat c.... Land near water has more stable temps b/c water acts as a heat sink 13

14 4.Geographic Position : a.Windward coast has more moderate temps. 1)Winds from ocean create more stable temps. b.Leeward coast temps are more like inland temps. 1)Winds come from inland, subject to greater changes in temp. c.Mountains can create barrier, reduce oceanic effects of temperature stability 1)Western side of Sierra-Nevada mtns. receives more rainfall than Eastern side of Sierra-Nevada. Nevada is a rain-shadow desert. 14

15 5.Cloud cover and albedo: Albedo: % of light reflected by an object a.Clouds reflect incoming solar radiation, keeps Earths surface cooler during daytime b.Clouds also reflect back infrared heat from Earths surface, keeps Earths surface night 15

16 6.Ocean currents redistribute heat around Earth: a.Carries warmer water from equator poles 1)England warmer than should be b/c of this warmer water b.Currents from poles bring cooler water toward tropics 16

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