Atmosphere and Climate

Atmosphere• Thin layer of gases that surrounds the Earth• Composed of:

– Nitrogen– Oxygen– Water vapor– Argon– Carbon dioxide– Neon– Helium– Other

Atmosphere has changed

• Early Earth’s atmosphere consisted only of methane, water vapor, ammonia and hydrogen

• Photosynthesis greatly changed our atmosphere!

Five Layers

Troposphere

• Earth’s surface to ~ 6 miles above the surface

• Contains ~ 90% of atmospheric gases

• Where weather occurs

Stratosphere

• 6 miles to about 30 miles above Earth’s surface

• Air is less dense

• Less turbulent air flow

• Contains the ozone layer

Mesosphere, Thermosphere,

Exosphere

• Gases become thinner and thinner

• Colder and colder

• Exosphere merges with outer space

Weather and Climate

• Weather: what is happening in the atmosphere at a particular time and place

• Climate: average weather in an area over a long period of time

Solar Radiation• The sun is 93 million miles away, but it has

a profound effect on our atmosphere

• The sun’s energy comes in many forms– Visible light passes through atmosphere– UV light is absorbed by ozone

– Infrared radiation is absorbed by CO2 & water

Solar radiation reacts with our atmosphere

• Absorption• Reflection• Scattered

• Energy re-emitted by the Earth is mainly heat energy… we’ll come back to this!

What determines Climate?

• Latitude

• Air circulation

• Ocean currents

• Local geography

Latitude• Distance from equator• Amount of solar

energy an area receives depends on latitude

Air Circulation• Important properties of air:

– Cool air sinks, and warms as it sinks– Warm air rises, and cools as it rises– Warm air can hold more water vapor than cool air

• Solar energy heats the ground• Due to these properties of air, winds are created

Air Circulation• Because different

latitudes receive different amounts of solar energy, different patterns of air circulation are created…

• These create the global patterns of precipitation

Global patterns of climate and precipitation create the different biomes we have learned about

Fig. 5-6, p. 103

Cell 3 North

Moist air rises — rain

Cell 2 North

Cool, dryair falls

Cell 1 North

Moist air rises,cools, and releasesMoisture as rain

Cell 1 South

Cool, dryair falls

Cell 2 South

Moist air rises — rain

Cell 3 South

Cold,dry airfalls

Polar cap

Temperate deciduousforest and grassland

Desert

Tropical deciduous forest

Tropicalrain forest

Equator

Tropical deciduous forest

Cold,dry airfalls

Polar capArctic tundra

Evergreenconiferous forest

Temperate deciduousforest and grassland

Desert

60°

30°

0°

30°

60°

The Coriolis Effect• Winds move in a straight line, but the Earth

rotates beneath them… creating a deflection– Always to the left in the southern hemisphere– Always to the right in the northern hemisphere

Winds• The air moving toward the equator from 30°

N or S is deflected by the Coriolis effect to form a wind that comes dominantly from the east, easterlies. These easterlies are also called the trade winds

• The air moving from 30°N or S to 60° N and S is deflected by the Coriolis effect to form a wind that comes dominantly from the west, westerlies

Ocean Currents• Water holds large amounts of heat

• Ocean currents are caused by winds and rotation of Earth

• Ocean currents influence climate by distributing heat from place to place and mixing and distributing nutrients.

Fig. 5-7, p. 104

(c) As concentrations of greenhouse gases rise, their molecules absorb and emit more infrared radiation, which adds more heat to the lower atmosphere.

(b) The earth's surface absorbsmuch of the incoming solar radiation and degrades it to longer-wavelength infrared (IR) radiation, which rises into the lower atmosphere. Some of this IR radiation escapes into space as heat, and some is absorbed by molecules of greenhouse gases and emitted as even longer-wavelength IR radiation, which warms the lower atmosphere.

(a) Rays of sunlight penetrate the lower atmosphere andwarm the earth's surface.

Ocean Currents• The easterlies push the ocean surface water across

the ocean just north (and just south) of the equator, forming an equatorial current.

• This equatorial current flows until it hits land. It is then deflected to the right in the northern hemisphere to form a western boundary current.

• In the North Atlantic, this current is called the Gulf Stream.

Ocean Currents• Western boundary currents bring warm water from

the equator to cooler, higher latitudes. • After flowing along the western side of the ocean,

the current deflects again, crossing the ocean. It reaches the eastern side and deflects again, running back to the equator as an eastern boundary current.

• Eastern boundary currents bring cool water from high latitudes toward the equator. In the Pacific, the eastern boundary current is called the California Current.

Animation: El Nino Southern Oscillation

PLAYANIMATION

The uneven heating of the planet by the sun drives the atmospheric and oceanic circulation, which in turn causes the Earth's climate to vary by latitude. We recognize climate zones, from equator to poles:

•tropics •subtropics •temperate •polar

In addition, climate may be marine or continental depending on how close to the ocean it is.

                

                                                           

Geography of the land• Topography of the land can greatly

affect climate

• Continents are places for extra heating

• Mountains shift winds upward and create added precipitation

Topography and Local Climate:Land Matters

• Interactions between land and oceans and disruptions of airflows by mountains and cities affect local climates.

Figure 5-8Figure 5-8

Climate• There are many factors that determine your

local climate, but ultimately it is… – Latitude– Air circulation– Ocean currents– Local geography

• And the most important factor of all… SOLAR ENERGY!!

BIOMES: CLIMATE AND LIFE ON LAND

• Different climates lead to different communities of organisms, especially vegetation.– Biomes – large terrestrial regions characterized

by similar climate, soil, plants, and animals.– Each biome contains many ecosystems whose

communities have adapted to differences in climate, soil, and other environmental factors.

BIOMES: CLIMATE AND LIFE ON LAND

Figure 5-9Figure 5-9

Fig. 5-10, p. 107

Polar

Rain forestTropical

seasonalforest

Scrubland

Savanna Desert

TropicalGrassland

Chaparral

DeciduousForest

Coniferous forest

Desert

Temperate

SubpolarTundra

Wet

Cold

Dry

Ho

t