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Chapter 4. Global Climates & Biomes. Structure of the Atmosphere. Density decreases as altitude increases (why?) Five layers of gases: Troposphere: 0 – 16 km (10 mi) Weather occurs here Temperatures drop with altitude Stratosphere: 16 – 50 km (10-31 mi) - PowerPoint PPT Presentation
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Global Climates & Biomes
Chapter 4
Density decreases as altitude increases (why?)Five layers of gases:
1. Troposphere: 0 – 16 km (10 mi) Weather occurs here Temperatures drop with altitude
2. Stratosphere: 16 – 50 km (10-31 mi) Higher altitudes are warmer (UV light) Ozone layer is located here
Ozone = O3 Absorbs UV radiation
3. Mesosphere4. Thermosphere5. Exosphere
Structure of the Atmosphere
The average weather in a given region over a long time
Affected by distribution of heat and precipitationUnequal heating of Earth’s surface:
Due to the curvature of the EarthAngle of sun’s raysAlbedo: the percentage of incoming sunlight that
is reflected from a surface; white reflects, colors absorbEarth’s average = 30%Tropics = 10-20%Snow-covered poles = 80-95%
Climate
Four properties of air that determine circulation:
1. Density – less dense (warm) air rises2. Water vapor capacity – warm air can hold
more water vapor – max amount is saturation point
3. Adiabatic cooling – air rises pressure decreases air expands in volume expansion lowers air temp
Adiabatic heating is the opposite4. Latent heat release – when water vapor
condenses into liquid water, energy is released
Atmospheric Convection Currents
1. The sun heats moist tropical air, causing it to rise2. The rising air experiences adiabatic cooling, water
vapor condenses into rain which falls back to Earth
3. The condensation of water vapor produces latent heat release, which makes the air expand and rise farther
4. The warm rising air displaces the cooler drier air above it, pushing it to the north and south
5. The cool dry air sinks and experiences adiabatic heating. It reaches Earth’s surface as warm dry air and then flows back toward the equator.
Formation of Hadley Cells: a type ofatmospheric convection current
ITCZ: intertropical convergence zoneThe area of Earth that receives the most
intense sunlightDense clouds and intense thunderstorm
activityNot at a fixed latitude – moves with the sun’s
angle throughout the yearLocated between 300 N and 300 S
Ferrel cells – 300 N & S to 600 N & SPolar cells - 600 N & S to the poles (900 N &
S)
Additional circulation cells
The equator rotates faster than the poles… This causes the winds to be deflected – this is
the Coriolis effecthttp://
www.youtube.com/watch?v=mcPs_OdQOYU
Besides all that, the Earth is spinning
The axis of rotation is angled 23.50 – the latitude that receives the most direct sunlight plus the most hours of sunlight changes throughout the year as Earth orbits the Sun
Spring Equinox (March) – Sun directly overhead – all regions get 12 hours of light + 12 hours of dark – spring begins in Northern Hemisphere; fall in Southern Hemisphere
Summer Solstice (June) – max tilt of Northern Hemisphere toward Sun – longest amount of daylight – summer begins
Fall Equinox (Sept) – opposite of March – day & night equalWinter Solstice (Dec) – max tilt of Northern Hemisphere
away from Sun – shortest daylight – winter begins
AND, the Earth is tilted on its axis
Don’t forget about all that ocean water!Ocean currents mix all the ocean waters and moderate the
temperatures of the continentsThese are influenced by:
temperature, gravity, prevailing winds, the Coriolis effect, & locations of continents
Warm water expands – tropical water surface is about 8 cm (3 in) higher water flows away from the equator
Gyres – large-scale patterns of ocean circulation: clockwise in Northern Hemisphere; counterclockwise in Southern
Upwellings – along the western coast of continents deeper , nutrient rich water rises – this supports large populations of producers and rich ecosystems
Thermohaline circulation – mixes surface water with deeper water – related to differing salinities
El Nino-Southern OscillationEvery 3-7 yearsSurface currents in the Pacific reverseGlobal impact:
Cooler & wetter conditions in SE U.S.Drier weather in southern Africa and SE Asia
Interaction of atmosphere & ocean
Local features can impact climateRain shadow
Mountain range forces air up and overOn the windward side, cooler air loses its
moistureOn the leeward side, air is drier deserts
Interaction of atmosphere & land
Terrestrial BiomesBiome – an area characterized by typical
plants and animals adapted to the yearly temperature and precipitation
Each biome contains many ecosystems whose communities are adapted to local variation in climate, soil, and other environmental factors
DesertsEvaporation > precipitation30% of EarthVariations in annual temp (red) and precip (blue)in tropical, temperate, and cold deserts
Human Impacts on Deserts
Large desert cities
Soil salinization from irrigation
Depletion of groundwater
Land disturbance and pollution from mineral extraction
Soil destruction from off-road vehicles
Tropical warm temps high humidity photosynthesis year-round
Temperate Deciduous forests:
seasonal changesbroad leaves dropped for cold winters
Rain forests: evergreens in cool, moist environment
Polar Taiga
long, cold wintersevergreens adapted to year-round photosynthesis
Forests – enough precip to support stands of trees
Human Impacts on Forests
Clearing for agriculture, livestock grazing, timber, and urban development
Conversion of diverse forests to tree plantations
Damage from off-road vehicles
Pollution of forest streams
Tropicalsavanna
Temperateprairie
Polartundra
Grasslands – less precip; fires common; soil extremely rich in temperate zone
Human Impacts on Grasslands
Conversion to cropland
Release of CO2 to atmosphere from grassland burning
Overgrazing by livestock
Oil production and off-road vehicles in artic tundra
Freshwater systems – low levels of dissolved salts
Streams and rivers: from mountains to oceansFlow creates different conditions and habitatsHeadwaters: cold, clear, rapidly moving water
with high levels of O2Downstream: slower moving, less O2, warmer
temps, more algae and cyanobacteria
Aquatic Ecosystems – affected by salinity, depth, and water flow
Standing water: lakes and pondsLife found in layers – temperature, sunlight,
dissolved O2, and nutrient availability changes with depth
Littoral zone: shallow area around shore; rooted vegetation
Limnetic zone: open offshore area; too deep for rooted plants; food chain begins with phytoplankton
Profundal zone: deep water without light; food chain depends on organisms above
Benthic zone: muddy bottom; nourished by decaying organic matter
Freshwater…
Wetlands – land is submerged part or all of the year but is shallow enough for rooted vegetation throughoutSwamps: contain treesMarshes: mainly nonwoody vegetation
(cattails)
Freshwater…
EstuariesSaltmarshes where rives flow into the ocean
Nutrient rich areas due to river flowMangrove swamps
Also produce nutrient rich mud
Marine biomes
Intertidal zoneNarrow strip between high and low tide mark
on the coastlineDifficult habitat for life
Marine biomes…
Coral reefsWarm, shallow water beyond the shoreline
Marine biomes…
The open oceanSunlight cannot penetrate to the bottomPhotic zone: enough light for photosynthesisAphotic zone: lacks light and therefore
photosynthesis
Marine biomes…