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…