1. Global Climates and biomes
Chapter 4
Global Climates and biomes

2. Atmosphere Weather is short term conditions of atmosphere
Climate is long term conditions
5 major processes influence climate/weather: unequal heating of earth, convection currents, Coriolis effect, tilt, and oceans
Atmosphere has 4-layers:
Troposphere (0-20km): bottom layer, densest, where most weather and mixing occurs, temps get colder with height
Stratosphere (20-50km): second layer, gets warmer with height, contains ozone layer that absorbs UV light
Mesosphere (50-80km) – third layer, coldest, meteorites burn up
Thermosphere – top layer, warmest, absorb gamma rays
Atmosphere protects organisms from radiation and it regulates temperatures

4. Past Climate Study
Trapped bubbles in ice cores provide a timescale of:
Atmospheric composition, greenhouse gas concentrations, temperature trends
Snowfall, solar activity, and frequency of fires
Ice cores go back 800,000 years
Cores in sediment beds preserve pollen grains and other plant remnants
Tree rings indicate age, precipitation, droughts, and fire history

6. 1. Unequal Heating Atmosphere is heated unevenly for 2 reasons
Tilt of the earth
Some areas on earth reflect more sunlight than other areas (albedo)
White surface has higher albedo than black surface
This uneven heating of the atmosphere drives convection currents in the atmosphere

8. 2. Atmospheric Convection Currents
Air has 4 properties that determine how it will circulate
Density: less dense air rises (warm), more dense air sinks (cold)
Water vapor capacity: warm air can hold more water vapor (saturation point) which is less dense
Adiabatic heating/cooling:
When air rises, pressure decreases and air expands and temps lower due to less friction between air molecules
When air sinks, pressure increases and air compresses and temps rise due to more friction between air molecules
Latent heat release: when air condenses, the energy that evaporated it is released and air warms

10. (2). Formation of Convection Currents
Air rises in warm, moist tropics
Rising air experiences lower atmospheric pressure and adiabatic cooling until it reaches saturation point
This leads to condensation which releases latent heat
Eventually air cools and spreads out and begins to sink around 30⁰ latitude (deserts)
When sinking air hits the ground, it spreads in all directions completing the cycle, called a Hadley cell
Air re-converges at the equator, called the intertropical convergence zone (ITCZ)
Polar regions cause additional Hadley cells

12. 3. Earth’s Rotation and Coriolis Effect
Earth rotates faster at equator than poles
Objects’ paths get deflected due to the rotation of earth. This is known as the Coriolis effect
This deflects winds and sets up weather patterns
Trade winds blow towards the equator between 0- 30°. They meet at the equator and rise creating calm winds called the doldrums
Where the air sinks at 30° is the horse latitudes
Air moves north from here, Coriolis force deflects it to right, and get westerlies (40°-60°)
At poles, the air sinks and moves towards the equator, but gets deflected to right. This creates polar easterlies

15. 4. Earth’s Tilt and Seasons
Earth is tilted 23.5⁰
When northern hemisphere is pointed towards the sun they experience summer
When northern hemisphere is pointed away from the sun they experience winter (southern hemisphere is opposite)
Vernal/automnal equinoxes, everywhere receives 12h daylight
Poles have 6 months of darkness and 6 months of daylight

18. 5. Ocean Currents
Currents driven by temp, gravity, prevailing winds, Coriolis effect, and continents
Water is warmer at the equator, so it expands and rises. This makes the water higher then the rest of earth and gravity takes over
Winds and Coriolis effect start ocean currents and deflect them. Called gyres (transport heat)
Upwelling (rising of water) occurs along coastlines
Thermohaline circulation is when water is saltier, making it more dense, so it sinks
ENSO (El Nino – Southern Oscillation– when ocean currents change direction, thus affecting climates (La Nina)

20. Rain Shadows
Air rises on one side of a mountain range and moisture condenses out
On other side, air sinks preventing clouds and it remains dry
Dry region is called a rain shadow

21. Altitudes create “latitudinal” patterns
Vegetative communities rapidly change along mountain slopes
The climate varies with altitude
A mountain climber in the Andes
Begins in the tropics and ends on a glacier
Rainshadow effect = air going over a mountain releases moisture
Creating an arid region on the other side

22. Biomes
Biomes are large regions characterized by a specific type of climate and certain types of plant and animal communities
Largest category scientists use to classify ecosystems
Each biome has many ecosystems
Biomes described by vegetation because that determines organisms and amount of vegetation is determined by climate
At altitude and latitude increase, temps decrease