2. The Physical Environment

Abiotic

physical environment

• Temperature, water, sunlight, pH, etc

biotic

living organisms:

• neighbors, competitors, predators, diseases, food, etc

Anthropogenic influences on the environment

human caused environmental changes

• ex: air pollution, building damns, etc

climate

long-term description of weather based on averages and variations measured over decades; includes daily and seasonal cycles, as well as yearly decadal cycles

weather

current conditions → temperatures, precipitation, humidity, cloud cover

Earths energy balance

the balance between incoming energy from thesun and outgoing energy from the earth 

greenhouses

impact the energy balance by trapping radiation which warms earth’s surface (H2O vapor, CO2, methane)

Determinants of climate

1. Global differences in solar radiation

2. Atmospheric currents and ocean currents

3. Regional influences of climate

Global differences in solar radiation

1. Latitudinal patterns

2. The tilt of Earth’s axis

1. Latitudinal patterns

position of Earth’s surface; spatial variation in temperature 

• North and South Pole= cold and energy from sun spread over large area, more atmosphere to get through

• Equator: warm and energy spreads over smaller area, less atmosphere to get thru

2. The tilt of Earth’s axis

affects angle of solar radiation

Atmospheric currents and ocean currents

1. Hadley cells

2. Polar cells

3. ferrel cells

4. Tropical zone versus temperate zone, versus polar zones

5. Intertropical Convergence Zone (ITCZ)

6. Atmospheric circulation and wind patterns

7. Major ocean surface currents

Influence of Hadley cells on global air pressure and precipitation patterns; parts of the Hadley cell

• large scale circulation patterns resulting from uplift in the tropics

• warm air rising creates low pressure

• cool air descending creates high pressures

• high pressure= dry= desert

• low pressure= tropics= at the equator; creates lots of precipitation 

Polar cells

are at the North and South Poles → cold air descends, creating higher pressure zones with little precipitation (polar deserts) (polar zones)

Ferrell Cells

exist at mid-latitudes and are influenced by Hadley and polar Cells and have ample precipitation (mostly) (temperate zones)

Tropical zone

• between 30 degrees North and South

• abundant precipitation  all seasons

• low pressure

• subtropics: wet/dry seasons

temperate zone

• between 30 and 60 degrees

• ample precipitation in all seasons

• low pressure

polar zones

• above 60 degrees

• sparse precipitation all seasons

• high pressure 

Intertropical Convergence Zone (ITCZ)

• where North and South hemisphere circulations meet

• rainy all year round

• much of earth’s precipitation originates here

• moves seasonally because of the tilt of earth’s axis

Tradewinds, westerlies, easterlies

• tradewinds: blow from East to West near the equator; air descends from high altitudes

• westerlies” blow from west to east in mid-latitudes in north and south hemisphere 

• easterlies: blow from east, near the poles

Coriolis effect

• the apparent deflection of air currents when viewed from a rotating reference  point such as Earth’s surface

• wind patterns interact with the shape of ocean basins to drive surface water currents

Major ocean surface currents

• great ocean conveyor belt

• driven by wind, temp, and salinity

• follows wind patterns

Regional influences of climate

1. Topography

2. Continentality

3. Albedo

topography

elevation, mountains

Rain shadows

• where little rainfall occurs in the “shadow” or downward side of mountain

• air rises over mountains, cools as it rises, cooling releases moisture 

santa anna winds

• tend to occur in fall

• cool, dry air originates in the Great Basin (high pressure in great basin)

• low pressure off the coast

• high velocity winds move east to west

• as winds move downslope:

  • air gets warmer

  • winds get faster

  • Humidity drops

Continentality

distance from the coast

Continentality → Effect on temperature variability

• cities further from the coast experience more variation in temperature 

• cities near coasts have similar average temperatures because water has a higher heat capacity than land

Albedo

the measure of reflectivity of a surface

• high albedo examples: snowy environment

• low albedo: dark forests

Vegetation influences on climate

• reflection (albedo)

• texture

• evapotranspiration= water loss thru transpiration by plants and from soil/other surfaces

• latent heat loss 

Short term cycles

Seasonal patterns in temperature and precipitation- earth’s inclination (23.5 degrees) causes seasonal changes

Decadal cycles

El Nino Southern Oscillation (ENSO)

a. Normal conditions versus ENSO conditions

• Normal: strong equatorial trade winds, upwelling along South America, and high rainfall in Western Pacific

• El Nino Conditions: weakened/reversed trade winds, reduced upwelling in South America, drought in Western Pacific

c. ENSO and La Nina in northern versus southern California

Southern California tends to be wetter during El Niño years and drier during La Niña years, but Northern California shows no consistent pattern.

d. Super blooms

el nino can stimulate germination and enhance survival and flowering