Climate and Biomes

Climate

Objectives:

Understand how weather is affected by:

1. Variations in the amount of incoming solar radiation

2. The earth’s annual path around the sun

3. The earth’s daily rotation

4. The world’s distribution of continents and oceans

5. The elevation of land masses

Climate and the Atmosphere

• Three layers– Outer mesosphere– Middle stratosphere (includes ozone

layer)– Inner troposphere (warmed by

greenhouse effect)

All weather takes place in Troposphere

Weather and Climate

• Weather: Current conditions—temperature, precipitation, humidity, cloud cover.

• Climate: Long-term average weather:– daily and seasonal cycles– yearly and decadal cycles.

Climate Change• Long-term change - results from:

– changes in distribution of solar radiation– changes in overall energy balance.

• Current climate change is due to– increased CO2 and other gases – caused by human activities.

Climate• Climate determines the geographic

distribution of organisms.

• Climate is characterized by average conditions; but extreme conditions are also important to organisms because they can contribute to mortality.

Widespread Mortality in Piñon Pines

1. Variations in the amount of incoming solar radiation

Latitudinal Differences in Solar Radiation at Earth’s Surface

Earth’s Energy Balance

Much of the solar radiation absorbed by Earth’s surface is emitted to the atmosphere as infrared radiation.

Latent heat flux: Heat loss due to evaporation.

Earth’s surface is also cooled when water at the surface evaporates and absorbs energy.

Climate• The atmosphere contains greenhouse

gases that absorb and reradiate the infrared radiation emitted by Earth.

– Water vapor (H2O)– Carbon dioxide (CO2)– Methane (CH4)– Nitrous oxide (N2O)

Climate• Without greenhouse gases, Earth’s

climate would be about 33°C cooler.

• Increased concentrations of greenhouse gases due to human activities are altering Earth’s energy balance, changing the climate system, and causing global warming.

2. The earth’s annual path around the sun

3. The earth’s daily rotation

Rotation and Wind Direction

• Earth rotates faster under the air at the equator than it does at the poles

• Deflection east and west

Global Air Circulation Patterns

• Hot air ascends; cold air descends• Warm air holds more moisture than cold air• As warm air ascends it cools, moisture condenses & creates precipitation• As cold descends it warms and picks up moisture from the surroundings

Tropical Heating and Atmospheric Circulation Cells

Summer Prevailing Wind Patterns

Winter Prevailing Wind Patterns

Atmospheric and Oceanic Circulation• Winds flow from areas of high pressure

to areas of low pressure, resulting in consistent patterns of air movements called prevailing winds.

• The winds appear to be deflected due to the rotation of the Earth—the Coriolis effect.

The Coriolis Effect on Global Wind Patterns

Wind Patterns

25,000 miles around the equator

Tropical rainforests

Deserts

Coniferous forests

Tundra

Northeasttradewinds

SoutheastTradewinds

(doldrums)

Westerlies(winds from the west)

Westerlies

Easterlies(winds from the east)

Easterlies

4. The world’s distribution of continents and oceans

Ocean and Climate

• 71% of Earth is covered with water

• Currents distribute solar heat and influence regional climates

• Currents redistribute nutrients

The Great Ocean Conveyor Belt

Global Ocean Surface Currents

Upwelling of Coastal Waters

Summer Prevailing Wind Patterns

Upwelling

Brings cold, nutrient-rich bottom waters to the surface

ENSO

• El Niño Southern Oscillation

• Climactic event that changes sea surface temperature and air circulation patterns in the equatorial Pacific Ocean

Between ENSOs

• Warm water and heavy rainfall move west across the Pacific

• Warm, moist air rises in the western Pacific, causing storms

• Upwelling of cool water along western coasts

clear skies, dry descending air

masses, high pressurewarm, moist, ascending

air masses, low pressure, storms in western Pacific

upwelling of cold water to 30-160 feet below surface

Fig. 31-27a, p.562

Between ENSOs

During an ENSO

• Trade winds weaken, and warm water flows east across the Pacific

• Sea surface temperatures rise

• Upwelling along western coasts ceases

• Heavy rainfall occurs along coasts, droughts elsewhere

clear skies, descending air masses, high pressure

warm, moist ascending air

masses, low pressure,

storms

rain falls in central Pacific

no upwelling; cold water as deep as 500 feet below surface

Fig. 31-27b, p.562

During an ENSO

El Niño

Near-absence of phytoplankton in the equatorial Pacific during an El Nino. Fig. 31-27c, p.562

Immense algal bloom in the equatorial Pacific in the La Nina rebound event. Fig. 31-27d, p.562

La Niña

5. The elevation of land masses

RainshadowEffect

Regional Climate Influences• On mountain slopes, shifts in vegetation

type reflect climate changes as temperature decreases and precipitation and wind speed increase with elevation.

The Rain-Shadow Effect

Rain Shadow

• Air rises on the windward side, loses moisture before passing over the mountain

Effects of Rain Shadow

Topography and elevation affect climate and zonal distribution of vegetation

Regional Climate Influences• Evapotranspiration: Water loss

through transpiration by plants, plus evaporation from the soil.

It transfers energy (as latent heat) and water into the atmosphere, thereby affecting air temperature and moisture.

The Effects of Deforestation Illustrate the Influence of Vegetation on Climate

Climate Variation over Long Time Scales

• The glacial–interglacial cycles have been explained by regular changes in the shape of Earth’s orbit and the tilt of its axis—Milankovitch cycles.

• The intensity of solar radiation reaching Earth changes, accentuating seasonal variation and resulting in climatic change.

Milankovitch Cycles and Long-Term Climate Variation

Milankovitch Cycles and Long-Term Climate Variation