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 CO 2 & 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, dry air falls Cell 1 North Moist air rises, cools, and releases Moisture as rain Cell 1 South Cool, dry air falls Cell 2 South Moist air rises — rain Cell 3 South Cold, dry air falls Polar cap Temperate deciduous forest and grassland Desert Tropical deciduous forest Tropical rain forest Equator Tropical deciduous forest Cold, dry air falls Polar cap Arctic tundra Evergreen coniferous forest Temperate deciduous forest 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 absorbs much 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 and warm 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 PLAY ANIMATION

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 5-8

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 5-9

Fig. 5-10, p. 107 Polar Rain forest Tropical seasonal forest Scrubland Savanna Desert Tropical Grassland Chaparral Deciduous Forest Coniferous forest Desert Temperate Subpolar Tundra Wet Cold Dry Hot