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Climate and Climate Change Environmental Science Spring 2011.

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Presentation on theme: "Climate and Climate Change Environmental Science Spring 2011."— Presentation transcript:

1 Climate and Climate Change Environmental Science Spring 2011

2 Objectives Explain the difference between weather and climate Identify four factors that determine climate Explain why different parts of the Earth have different climates Explain what causes the seasons

3 Weather and Climate Weather: is the state of the atmosphere at a particular place at a particular moment Climate: is the long-term prevailing weather conditions at a particular place based upon records taken

4 Weather and Climate Phoenix, AZ and Seattle, WA may have the same weather on a particular day (may be warm in both places), but climates are quite different (Phoenix is hot and dry, Seattle is cool and moist)

5 Factors Determining Climate Latitude Most important is distance from equator Atmospheric circulation patterns Oceanic circulation patterns Local geography of an area Solar activity Volcanic activity

6 Latitude Latitude: the distance from the equator measured in degrees north or south of the equator Equator: located at zero degrees latitude North Pole: most northerly latitude, 90 degrees north South Pole: most southerly latitude, 90 degrees south

7 Latitude Latitude influences climate because the amount of solar energy an area of Earth receives depends on its latitude

8 Latitude Low latitude More solar energy falls on areas that are near equator Incoming solar energy is concentrated on a relatively small surface area at the equator In areas near equator night and day are about 12 hours long throughout the year Temperatures are high year round, no summers or winters

9 Latitude High latitude In regions close to poles, amount of energy arriving at surface is reduced In northern and southern latitudes, sunlight hits Earth at oblique angle and spreads over a larger surface area Average temperatures are lower Hours of daylight vary

10 Atmospheric Circulation Air circulation affects climate Cold air sinks because it is denser than warm air As cold air sinks, it compresses and gets warmer Warm air rises Expands and cools as it rises Warm air can hold more water vapor than cold air can When warm air cools, the water vapor it contains may condense (rain)

11 Atmospheric Circulation Solar energy heats the ground Warms the air above ground Warm air rises and cooler air moves in to replace it Wind: the movement of air within atmosphere

12 Atmospheric Circulation Because Earth rotates, and because different latitudes receive different amounts of solar energy, pattern of global atmospheric circulation results Determines Earth’s precipitation pattern

13 Global Circulation Patterns Cool air over equator cannot sink because hot air is rising below it Cool air rises and is forced away from the equator

14 Global Circulation Patterns At about 30 degrees north and south latitude, some of cool air sinks, becomes warmer as sinks Warm, dry air moves across land and causes water to evaporate from land below, which creates dry conditions

15 Global Circulation Patterns At about 60 degrees north and south latitude, air collides with cold air traveling from poles Warm air rises When rising air reaches top of troposphere, small amounts return back to circulation patterns between 60 and 30 degrees north and south latitude Most of uplifted air is forced toward poles Cold dry air descends at poles (cold deserts)

16 Prevailing Winds Prevailing winds: winds that blow in mostly one direction throughout the year Because of rotation of Earth, deflected to the right in the Northern hemisphere and to the left in the Southern hemisphere

17 Prevailing Winds Trade Winds: belts of prevailing winds between 30 degrees north and south latitudes and the equator Blow from the northeast in Northern hemisphere and southeast in the Southern hemisphere

18 Prevailing Winds Westerlies: produced between 30 and 60 degrees north and south latitudes Northern hemisphere these westerlies are southwest winds Southern hemisphere these westerlies are northwest winds

19 Prevailing Winds Polar Easterlies: blow from poles to 60 degrees north and south latitudes

20 Oceanic Circulation Patterns Movement of surface ocean currents is caused mostly by winds and rotation of Earth Redistribute warm and cool masses of water

21 Oceanic Circulation Patterns El Nino- Southern Oscillation El Nino and La Nina are opposite phases of ENSO El Nino warmer phase, La Nina colder phase El Nino Short term (6-18 months) periodic change in location of warm and cold water masses in the Pacific Ocean Warm water pushed eastward Increased rainfall eastward (southern half of US) La Nina Water in the eastern Pacific Ocean is cooler than usual

22 Oceanic Circulation Patterns Pacific Decadal Oscillation Long term, 20 to 30 year change in location of warm and cold water masses in Pacific Ocean Influences climate in northern Pacific Ocean and North America Affects ocean surface temperatures, air temperatures, and precipitation patterns

23 Topography Elevation effects climate Temperatures fall by about 6 degrees C for every 11,000m increase in elevation

24 Topography Mountains and mountain ranges influence distribution of precipitation Sierra Nevada mountains When warm air hits mountains it rises As air rises, it cools, which causes rain on western side of mountains By the time air reaches eastern side of mountains, it is dry Rain shadow effect

25 Other Influences on Earth’s Climate Solar maximum: sun emits an increased amount of UV radiation UV produces more ozone, warming the stratosphere Increased radiation can also warm the lower atmosphere and surface of the Earth a little

26 Other Influences on Earth’s Climate Large scale volcanic eruptions Sulfur dioxide gas can reach the upper atmosphere Sulfur dioxide reacts with smaller amounts of water vapor and dust in stratosphere Reaction forms a bright layer of haze that reflects enough sunlight to cause global temperature to decrease

27 Seasonal Changes in Climate Seasons result from tilt of Earth’s axis (about 23.5 degrees relative to the plane of its orbit) Because of tilt, the angle at which the sun’s rays strike the Earth changes as the Earth moves around the sun

28 Seasonal Changes in Climate During summer in Northern Hemisphere, the Northern Hemisphere tilts toward the sun and receives direct sunlight Number of daylight is greatest During summer in Northern Hemisphere, the Southern Hemisphere tilts away from the sun and receives less direct sunlight During summer in Southern Hemisphere, situation is reversed Southern Hemisphere tilted toward sun, Northern hemisphere tilted away

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