Climate and the Atmosphere

Transcription

1 Climate and Biomes

2 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

3 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

4 Weather and Climate Weather: Current conditions temperature, precipitation, humidity, cloud cover. Climate: Long-term average weather: daily and seasonal cycles yearly and decadal cycles.

5 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 CO 2 and other gases caused by human activities.

6 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.

7 Widespread Mortality in Piñon Pines

8 1. Variations in the amount of incoming solar radiation

9 Latitudinal Differences in Solar Radiation at Earth s Surface

10 Earth s Energy Balance

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

12 Earth s surface is also cooled when water at the surface evaporates and absorbs energy. Latent heat flux: Heat loss due to evaporation.

13 Climate The atmosphere contains greenhouse gases that absorb and reradiate the infrared radiation emitted by Earth. Water vapor (H 2 O) Carbon dioxide (CO 2 ) Methane (CH 4 ) Nitrous oxide (N 2 O)

14 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.

15 2. The earth s annual path around the sun

16 3. The earth s daily rotation

17 Rotation and Wind Direction Earth rotates faster under the air at the equator than it does at the poles Deflection east and west

18 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

19 Tropical Heating and Atmospheric Circulation Cells

20 Summer Prevailing Wind Patterns

21 Winter Prevailing Wind Patterns

22 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.

23 The Coriolis Effect on Global Wind Patterns

24 Wind Patterns Tundra Coniferous forests Deserts Tropical rainforests Easterlies (winds from the east) Westerlies (winds from the west) Northeast tradewinds (doldrums) Southeast Tradewinds Westerlies Easterlies 25,000 miles around the equator

25 4. The world s distribution of continents and oceans

26 Ocean and Climate 71% of Earth is covered with water Currents distribute solar heat and influence regional climates Currents redistribute nutrients

27 The Great Ocean Conveyor Belt

28 Global Ocean Surface Currents

29 Upwelling of Coastal Waters

30 Summer Prevailing Wind Patterns

31 Upwelling Brings cold, nutrient-rich bottom waters to the surface

32 ENSO El Niño Southern Oscillation Climactic event that changes sea surface temperature and air circulation patterns in the equatorial Pacific Ocean

33 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

34 warm, moist, ascending air masses, low pressure, storms in western Pacific Between ENSOs clear skies, dry descending air masses, high pressure upwelling of cold water to feet below surface Fig a, p.562

35 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

36 clear skies, descending air masses, high pressure During an ENSO 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 b, p.562

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

38 La Niña Immense algal bloom in the equatorial Pacific in the La Nina rebound event. Fig d, p.562

39 5. The elevation of land masses Rainshadow Effect

40 Regional Climate Influences On mountain slopes, shifts in vegetation type reflect climate changes as temperature decreases and precipitation and wind speed increase with elevation.

41 The Rain-Shadow Effect

42 Rain Shadow Air rises on the windward side, loses moisture before passing over the mountain

43 Effects of Rain Shadow

44 Topography and elevation affect climate and zonal distribution of vegetation

45 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.

46 The Effects of Deforestation Illustrate the Influence of Vegetation on Climate

47 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.

48 Milankovitch Cycles and Long-Term Climate Variation

49 Milankovitch Cycles and Long-Term Climate Variation