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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