1. Global Climates & Biomes
Chapter 4
Global Climates & Biomes

2. 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)
Higher altitudes are warmer (UV light)
Ozone layer is located here
Ozone = O3
Absorbs UV radiation
Mesosphere
Thermosphere
Exosphere

3. Climate The average weather in a given region over a long time
Affected by distribution of heat and precipitation
Unequal heating of Earth’s surface:
Due to the curvature of the Earth
Angle of sun’s rays
Albedo: the percentage of incoming sunlight that is reflected from a surface; white reflects, colors absorb
Earth’s average = 30%
Tropics = 10-20%
Snow-covered poles = 80-95%

4. Atmospheric Convection Currents
Four properties of air that determine circulation:
Density – less dense (warm) air rises
Water vapor capacity – warm air can hold more water vapor – max amount is saturation point
Adiabatic cooling – air rises  pressure decreases  air expands in volume  expansion lowers air temp
Adiabatic heating is the opposite
Latent heat release – when water vapor condenses into liquid water, energy is released

5. Formation of Hadley Cells: a type of atmospheric convection current
The sun heats moist tropical air, causing it to rise
The rising air experiences adiabatic cooling, water vapor condenses into rain which falls back to Earth
The condensation of water vapor produces latent heat release, which makes the air expand and rise farther
The warm rising air displaces the cooler drier air above it, pushing it to the north and south
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.

7. ITCZ: intertropical convergence zone
The area of Earth that receives the most intense sunlight
Dense clouds and intense thunderstorm activity
Not at a fixed latitude – moves with the sun’s angle throughout the year
Located between 300 N and 300 S

8. Additional circulation cells
Ferrel cells – 300 N & S to 600 N & S
Polar cells N & S to the poles (900 N & S)

9. Besides all that, the Earth is spinning
The equator rotates faster than the poles…
This causes the winds to be deflected – this is the Coriolis effect

10. AND, the Earth is tilted on its axis
The axis of rotation is angled – 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 equal
Winter Solstice (Dec) – max tilt of Northern Hemisphere away from Sun – shortest daylight – winter begins

12. Don’t forget about all that ocean water!
Ocean currents mix all the ocean waters and moderate the temperatures of the continents
These 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

14. Interaction of atmosphere & ocean
El Nino-Southern Oscillation
Every 3-7 years
Surface currents in the Pacific reverse
Global impact:
Cooler & wetter conditions in SE U.S.
Drier weather in southern Africa and SE Asia

16. Interaction of atmosphere & land
Local features can impact climate
Rain shadow
Mountain range forces air up and over
On the windward side, cooler air loses its moisture
On the leeward side, air is drier  deserts

18. Terrestrial Biomes
Biome – 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

21. Deserts Evaporation > precipitation 30% of Earth
Variations in annual
temp (red) and precip (blue)
in tropical, temperate, and
cold deserts

22. 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

23. Forests – enough precip to support stands of trees
Tropical
warm temps
high humidity
photosynthesis
year-round
Temperate
Deciduous forests:
seasonal changes
broad leaves dropped for
cold winters
Rain forests:
evergreens in cool,
moist environment
Polar
Taiga
long, cold winters
evergreens adapted to
year-round photosynthesis

24. 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

25. Grasslands – less precip; fires common; soil extremely rich in temperate zone
Tropical
savanna
Temperate
prairie
Polar
tundra

26. 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

27. Aquatic Ecosystems – affected by salinity, depth, and water flow
Freshwater systems – low levels of dissolved salts
Streams and rivers: from mountains to oceans
Flow creates different conditions and habitats
Headwaters: cold, clear, rapidly moving water with high levels of O2
Downstream: slower moving, less O2, warmer temps, more algae and cyanobacteria

28. Freshwater… Standing water: lakes and ponds
Life 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

30. Freshwater…
Wetlands – land is submerged part or all of the year but is shallow enough for rooted vegetation throughout
Swamps: contain trees
Marshes: mainly nonwoody vegetation (cattails)

31. Marine biomes Estuaries Saltmarshes where rives flow into the ocean
Nutrient rich areas due to river flow
Mangrove swamps
Also produce nutrient rich mud

32. Marine biomes… Intertidal zone
Narrow strip between high and low tide mark on the coastline
Difficult habitat for life

33. Marine biomes…
Coral reefs
Warm, shallow water beyond the shoreline

34. Marine biomes… The open ocean Sunlight cannot penetrate to the bottom
Photic zone: enough light for photosynthesis
Aphotic zone: lacks light and therefore photosynthesis