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GEOG101 Chapter 4 Lecture
 

GEOG101 Chapter 4 Lecture

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    GEOG101 Chapter 4 Lecture GEOG101 Chapter 4 Lecture Presentation Transcript

    • Overview
      • Air Temperature
      • Air Pressure and Winds
      • Ocean Currents
      • Moisture in the Atmosphere
      • Climate Regions
      • Climatic Change
    • Weather vs. Climate
      • Weather
        • State of the atmosphere at a given time and place
      • Climate
        • Long-term average weather conditions in a place
      • Troposphere is of particular concern
        • Atmospheric layer closest to the earth
        • Contains virtually all of the air, clouds, and precipitation of the earth
    • Air Temperature
      • Insolation
        • Solar radiation received at the earth’s surface
          • Determined by angle of the sun’s rays and number of daylight hours
      • Modifying variables
        • Amount of water vapor in the air
        • Cloud cover
        • Nature of the surface of the earth
        • Elevation
        • Degree and direction of air movement
    • Earth Inclination
      • Axis of the earth tilts at ≈ 23.5°
      • Summer Solstice (about June 21)
        • Northern hemisphere tilted toward the sun
        • Vertical rays of the sun at 23.5° N
      • Winter Solstice (about December 21)
        • Northern hemisphere tilted away from the sun
        • Vertical rays of the sun at 23.5° S
      • Spring and fall equinoxes (about March 21 and September 21)
        • Vertical rays of the sun at equator
    • Earth Inclination
      • Variation in length of days and nights
        • At the equator
          • 12 hours of light each day of the year
        • Inside the Arctic Circle and Antarctic Circle
          • 24 hours of daylight/darkness on solstice
      • Angle of the sun’s rays
        • More direct angle = more energy available
    • Reflection and Reradiation
      • Clouds and light colored surfaces reflect solar energy
      • Reradiation
        • Shortwave solar energy absorbed, returned into the atmosphere as longwave terrestrial radiation
      • Water heats and cools more slowly
        • Marine environment
          • Cooler summers, warmer winters
      • Land heats and cools more rapidly
        • Continental environment
          • Hotter summers, colder winters
    • The Lapse Rate
      • Temperature generally decreases as altitude increases
        • Lapse rate
          • Average of 3.5° F per 1000 feet (6.4 ° C per 1000 m)
      • Temperature inversion
        • Cooler air trapped below warmer air
          • Contributes to smog problems
    • Air Pressure and Winds
      • Weight of the atmosphere
      • Air pressure is higher closer to the earth’s surface
      • Temperature and air pressure
        • Cold air is denser: high pressure
        • Warm air is lighter: low pressure
      • Air pressure is measured by a barometer
    • Air Pressure and Winds
      • Zones of high and low air pressure
      • Pressure gradient force
        • Causes air to flow from high to low pressure areas
        • Wind
          • Velocity is in direct proportion to pressure differences
      • Convection
        • Circulatory movement of rising warm air and descending cool air
    • Air Pressure and Winds
      • Land and sea breezes
        • Day: from sea to land
        • Night: from land to sea
      • Mountain and valley breezes
        • Day: from valley to mountains
        • Night: from mountains to valley
    • Air Pressure and Winds
      • Coriolis effect
        • Apparent deflection relative to the earth’s surface
          • Northern Hemisphere: wind veers toward the right Southern Hemisphere: wind veers toward the left
        • Spiral wind patterns
      • Frictional effect
        • Decreases wind speed
        • Changes wind direction
    • Global Air-Circulation Pattern
      • Equatorial low pressure
      • Subtropical high pressure
        • About 30 ° N and 30° S of the equator
      • Trade winds
        • In the tropics
      • Westerlies
        • In the midlatitudes
      • Subpolar low
      • Polar easterlies
      • Polar high
    • Global Air-Circulation Pattern
      • Jet streams
        • Belts of strong winds in the upper atmosphere
          • From west to east
        • Guide the movement of weather systems
      • Monsoon
        • Wind system that reverses direction seasonally
          • Produces wet and dry seasons
        • Significant effect on parts of southern and eastern Asia
          • Farm economy is dependent upon summer monsoon rains
          • Flooding
    • Ocean Currents
      • Movement due to winds and differences in water density
        • Direction also influenced by landmasses and shape of ocean basins
      • North Atlantic drift
      • Ocean currents affect temperature and precipitation on adjacent land areas
        • Cold currents
          • Dry conditions
        • Warm currents
          • Moist conditions
    • Moisture in the Atmosphere
      • Ascending air expands and cools
        • Less able to hold water vapor
      • Supersaturated air
        • Water vapor condenses around condensation nuclei
      • Clouds
        • Rain droplets or ice crystals supported by upward movements of air
          • Droplets may coalesce and fall as precipitation
        • Form and altitude depends on:
          • Water vapor content, temperature, wind movement
    • Moisture in the Atmosphere
      • Relative humidity
        • Percentage measure of the moisture content of the air
          • Amount present relative to the maximum that can exist at the current temperature
      • Dew point
        • Temperature at which condensation forms
    • Types of Precipitation
      • Convectional precipitation
        • Heated, moisture-laden air rises and then cools below the dew point
        • Summer in tropical and continental climates
      • Orographic precipitation
        • Warm, moisture-laden air is forced to rise over hills or mountains and is thereby cooled
          • Windward side
            • Receives a great deal of precipitation
          • Leeward side
            • Very often dry (rain shadow)
    • Types of Precipitation
      • Cyclonic (frontal) precipitation
        • Cool and warm air masses meet
        • Common to the midlatitudes
        • In the tropics—originator of hurricanes and typhoons
        • Air mass
          • Body of air with similar temperature, pressure, and humidity characteristics throughout
          • Form over a source region
        • Front
          • Zone of separation between two air masses
    • Storms
      • Cyclone
        • Masses of air circulate rapidly about a region of low atmospheric pressure
        • Can develop into a storm
      • Hurricane
        • Severe tropical cyclone with winds exceeding 75 mph
        • In the Atlantic, Caribbean, or Gulf of Mexico
      • Typhoon
        • Hurricane in the western Pacific
    • Storms
      • Blizzard
        • Heavy snow and high winds
      • Tornado
        • Funnel-shaped cloud of whirling winds that can form beneath a cumulonimbus cloud and moves at speeds as high as 300 mph
        • Esp. Central U.S.
    • Climate Regions
      • Generalizations based on daily and seasonal weather conditions
      • K öppen system
        • Based on temperature, precipitation, and natural vegetation criteria
        • A: tropical
        • B: dry
        • C: mild midlatitude
        • D: midlatitude with cold winters
        • E: polar
        • H: highland
    • Tropical Climates
      • Tropical rainforest
        • Equatorial low pressure
        • High temperatures and heavy convectional rainfall all year
        • Dense forests
        • Lack of soil nutrients
    • Tropical Climates
      • Tropical savanna
        • To the north and south of rain forests
        • High temperatures
        • Heavy convectional rainfall in summer, dry winters
        • Forests to grasslands
      • Tropical monsoon
        • Significant increase in rainfall when summer monsoon winds bring water-laden air
        • Dense forests
    • Dryland Climates
      • Hot deserts
        • Subtropical high pressure
        • Considerable sunshine, high temperatures
        • Very little precipitation
        • Shrubs in gravelly or sandy environments
      • Midlatitude deserts and semideserts
        • Warm/hot summers and cold winters
        • Some convectional or frontal rainfall in summer, some snowfall in winter
        • Grasslands, desert shrubs
        • Steppes have fertile soils
    • Humid Midlatitude Climates
      • Mediterranean
        • Transition zone between subtropical high and westerlies
        • Warm/hot summers and mild/cool winters
        • Dry summer, frontal precipitation in winter
        • Shrubs and small deciduous trees
      • Humid subtropical
        • Hot, moist summers and moderate, moist winters
        • Convectional rainfall in summer, frontal precipitation in winter
        • Deciduous and coniferous forests
    • Humid Midlatitude Climates
      • Marine west coast
        • Prevailing winds from the sea
        • Moderate temperatures in both summer and winter
        • Frontal and orographic precipitation
        • Deciduous and coniferous forests
      • Humid continental
        • Prevailing winds from the land
        • Hot/mild summers and cool/cold winters
        • Frontal and occasionally convectional rainfall in summer, snow in winter
        • Deciduous and coniferous forests
    • Arctic and Subarctic Climates
      • Subarctic
        • Cool/cold, short summers and very cold winters
        • Coniferous forest to mosses and lichens
        • Tundra
          • Treeless area between the Arctic tree line and the permanently ice-covered zone
      • Arctic
        • Ice cap near the poles
        • Extremely cold with light precipitation
    • Highland Climates
      • Lower temperatures than lowlands at the same latitude
      • Variety of conditions based on:
        • Elevation
        • Prevailing winds
        • Orientation of slope relative to the sun
        • Valley, slope, or peak
        • Ruggedness
    • Climatic Change
      • Long-term climatic change
        • Significant variations over geologic time
          • Ice ages
          • Medieval warm period and “little ice age”
        • May be due to variations in: shape of Earth’s orbit, tilt of the axis, gyration of the rotation axis
      • Short-term climatic change
        • Natural processes
          • Volcanic eruptions, oceanic circulation, sunspot activity
        • Human processes
          • Enhanced greenhouse effect
    • Climatic Change
      • Greenhouse effect
        • Certain gases in the atmosphere function as an insulating barrier, trapping infrared radiation
      • Global warming
        • Caused by human activities that have increased the amount of greenhouse gases in the atmosphere
          • Carbon dioxide: burning fossil fuels, deforestation
          • Methane: natural gas and coal mining, agriculture and livestock, swamps, landfills
          • Nitrous oxides: motor vehicles, industry, fertilizers
          • Chlorofluorocarbons: industrial chemicals
    • Climatic Change
      • Evidence of global warming
        • 20 th century was the warmest in 600 years
          • Average surface temp rose over 1 ° F during the century
        • Winter temps in the Arctic have risen about 7° F since the 1950s
          • Loss of Arctic ice cap
        • Glaciers are thinning and retreating
      • Consequences of global warming include:
        • Rising sea levels
        • Changes in temperature and precipitation patterns
          • Impact on soils, vegetation, agriculture