Chapter 7: Climate & Terrestrial Biodiversity
Weather
 Local physical properties of troposphere
o Temperature, Pressure, Humidity, Cloudiness, Wind
Climate
 Pattern of atmospheric conditions over long periods of time
 Determined by…
o Ocean currents distributing heat & moisture
o Global air circulation patterns
Troposphere (0-10ish miles up)
 Temp decreases w/ altitude
 Most of atmospheric gases
 Weather
 Tropopause = top
Air Circulation Factors
 Uneven heating of Earth’s surface by Sun
o Equator hit at direct angle
o Poles hit at slanted angle
o Seasons
 Variations of light & temp increase steadily toward poles
 Poles have more pronounced seasons
 Earth’s tilt – 23.5 degrees
 March Equinox – Sun faces equator
 All regions have 12 hrs day/night
 June Solstice – N. Hemisphere faces sun (Summer)
 Longest day/Shortest night
 S. Hemisphere opposite
 September Equinox – Sun faces equator
 All regions have 12 hrs day/night
 December Solstice – N.H. tilts away from sun (Winter)
 Shortest day/Longest Night
 S. Hemisphere opposite
o Greenhouse Effect
 Absorb & reflect IR radiation bouncing off ground; warms troposphere & surface
 CO2, N2O (nitrous oxide), O3, CH4, H2O, halocarbons (CFC)
 Global warming potential - relative ability of GHG to contribute to global warming
o Albedo (Reflectivity)
 Measure of how well a substance reflects sunlight
1. Snow (fresh best)
3. Land
2. Ice
4. Water
 Air, Water, & Land properties
o Convection Circulation
 Convection – transfer of heat via liquid & gas
 Air heated at surface; picks up moisture
 Warm air rises; cools/ condenses forming clouds & precipitation
 Dry, cool air descends/ warms; restarts cycle
 Driving Forces
 Horizontal air movement = pressure differences; moves high to low
 Lateral air movement = density (i.e. temp) differences; warm rises/cool descends
o Global Convection Cells
 Hadley Cells – warm air rises at equator & cool falls at 30°
 Ferrel Cells – cool air falls at 30° & warm rises at 60° (Opposite air circulation)
 Polar Cells – warm rises at 60° & cool falls at 90°
o
General Climate Patterns
 Wet/Tropical at equator
 Dry/Warm around 30°
 Wet/Temperate around 60°
 Dry/Cold near poles
 Rotation of Earth on its axis
o Coriolis Effect
 Rotation causes equator to spin faster than poles
 Winds are deflected & curved (right in North, left in South)
o Prevailing Winds
 Equator = Doldrums (no wind)
 Equator – 30° = NE Trade Winds (North) & SE Trade Winds (South)
 30° – 60° = Westerlies
 60° – 90° = Polar Winds
o Oceanic Currents
 Surface currents caused by prevailing winds
 Oceanic Conveyor Belt
 Vertical mixing & global movement of oceans
 Thermohaline Circulation – powered by salt & temperature differences (water
density)
o Also affected by continent positions & winds
Local Weather
 Warm Front – warm air mass displaces cold air mass (moderate precipitation)
 Cold front – cold air mass displaces warm air mass (heavy precipitation)
Beach City Moderation
 Daily Air Currents by Water
o Daytime
 Air rises over warm land
 Draws cool breeze from water over land
o Nighttime
 Land cools
 Air rises over warmer water
 Draws cooler air from land back over water
 Land gets warmer air from offshore
Smog Problems
 Thermal Inversion
o Cold air is trapped under hot air
 Areas of upwelling (Cali coast)
 Mountain shaded valleys (L.A.)
o Inversion layer – band w/ cold air on bottom, warm on top
 Resists mixing; density difference
 Traps air pollution
Heat Island Effect
 Urban areas warmer than surroundings
 Buildings slow winds
 Cement, buildings tend to absorb heat
 Often less vegetation
 Factories, cars, people release heat
Rain Shadow Effect
 Windward Side (faces water)
o Hit by warm moist air from ocean, which rises, cools, & drops precipitation
 Leeward Side (opposite water)
o Cool, dry air descends
Milankovitch Cycles
 3 changes in Earth’s rotation & orbit
o Alter solar radiation
o Trigger long term climate changes
 Axial Wobble (19-23,000 yr cycle)
 Tilt Change (41,000 yr cycle)
o Slow change
o 22.4 & decreasing right now
 Orbit Change (100,000 yr cycle)
o Circular to elliptical
North Atlantic Deep Water (NADW)
 Warm equatorial water moves to North Atlantic
o Cools (releases heat), condenses, sinks (hi salinity)
 Slowed or Stopped?
o Europe & N. America screwed
El Niño Southern Oscillation (ENSO)
 Normal Loop
o NE & SE trade winds push warm water west (Indonesia)
 8° warmer
 20 inches higher
o Cold upwelling by Peru
 El Niño
o Every 2-7 yrs
 Equatorial winds weaken or reverse
 Warm water flows east to Peru; Prevents cold upwelling (nutrients) in E. Pacific
 Alters global weather
o Effects
 S. America fisheries hurt
 Warm water gives rise to heavy precipitation
 Dry areas soaked & Wet areas dry
 La Niña
o Opposite effect
o Colder surface water extends far westward
Tornadoes
 Form over land
 Spin up to 300 mph
 Large mass of dry air hits large mass of humid air
o Cool descends as Warm rises
 Fujita Scale – F5 strongest
o Based on damage done
Hurricanes
 Low pressure area over warm water pulls air from surrounding high pressure
 Eye – low pressure center
 Eye wall – area right around eye; most extreme weather
 Hurricane Strength
o Category 1 – 74-95 mph
o Category 4 – 131-155 mph
o Category 2 – 96-110 mph
o Category 5 – 155+ mph
o Category 3 – 111-130 mph
Earth’s Land Biomes
 Regions w/ similar climate (temp & precipitation), soil, plants, & animals
o Tropical – hot
o Temperate – moderate
o Polar – cold
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Deserts
o Low rainfall (<10 inches)
o Fragile ecosystem & soil
 Slow plant growth
 Low species diversity
 Slow nutrient recycling
 Lack of water
o Humans & Deserts
 Large desert cities
 Depletion of groundwater
 Mineral extraction pollution
 Soil salinization from irrigation
 Nuclear Tests
 SUV connection – break up soil, increase erosion
 Only expanding biome
Grasslands
o Normally inland; too moist for desert, too dry for forest
o Persist due to seasonal drought, grazing by large herbivores, & fires
o Savanna
 Warm year-round; wet & dry seasons
 Scattered trees; plants adapted for drought
 Deep roots; small leaves
 Herds of grazers move w/ seasons
o Temperate Grassland
 Summers hot & dry; winters cold
 Uneven rainfall thru year
 Winds & fire slow tree growth
 Grasses adapted to fire (deep roots aren’t killed)
 Very rich soil (good for farming)
o Arctic Tundra
 Above tree line; very cold & windy; little precipitation
 Under snow: grasses, mosses, lichens, shrubs
 Animals have thick fur
 Permafrost – soil w/ frozen water
o Humans & Grasslands
 Convert to croplands
 Release CO2 from burning land
 Overgrazing
 Oil production & off-road vehicles (tundra)
 Global warming melting permafrost; releases CO2 & CH4
Chaparral (Temperate Shrubland)
o Usually border coasts & deserts
o More rain than desert
o Long, warm, dry summers: Very fire-prone
o Dominated by shrubs
o Utilized for urbanization
Forests
o Tropical Rain Forests
 Warm & moist year round (75+ inches); very high NPP
 Dominated by broadleaf evergreens; very specialized plants/animals
 Little wind = animal seed dispersal
 Poor topsoil
 Fast decomposition (warm/moist)
 Soil leaching from rains
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Temperate Deciduous Forests
 Moderate temps; heavy seasons
 Long, warm summers & not too severe winters; abundant rain
 Dominated by broadleafs (oak, hickory, maple, poplar)
 Survive winter by dropping leaves & going dormant
 Most disturbed biome
Coniferous Forests
 aka Boreal Forest or Taiga
 Largest land biome
 Long, cold, dry winters & short summers (cool to warm)
 Dominated by evergreens (pine, spruce, fir, cedar)
 Needle-shaped leaves; waxy cuticle to withstand cold
 Slow decomposition; acidic pH
Humans & Forests
 Clearing for farms, grazing, timber, urbanization
 Convert to monoculture farms
 Off-road vehicles
 Pollution of streams