CHAPTER 7

• Weather


  Set of physical conditions of the lower atmosphere in an area over a period of hours to days
• Weather


  • Atmospheric temperature and precipitation
• Weather affected by


  1. Moving masses of warm or cold air

  2. Atmospheric pressure changes

  3. Occasional shifts in major winds
• Front


  Boundary between two air masses with different temperatures and densities

  
• Warm front


  Advancing warm air mass rises up over cooler air, moisture begins to condense and forms layers of clouds at different altitudes
• Cold front


  Advancing cold air mass stays close to the ground, wedging below warmer air, produces rapidly moving, towering clouds called thunderheads that can cause high surface winds and thunderstorms
• High-pressure air mass


  Contains cool, dense air that descends slowly, lack of condensation leads to dry weather
• Low-pressure air mass


  Contains low-density, warm air that rises, expands, and cools, condensation may lead to precipitation
• Jet streams


  Powerful winds that circle the globe
• El Niño–Southern Oscillation (ENSO)


  Periodic change in wind patterns in the Pacific Ocean that can alter conditions over two-thirds of the world
• Tornadoes


  Violent weather event that forms over land, with vertical convection currents sucking air upward, most occur in the Midwestern United States due to collision of cold and warm air masses
• Tropical cyclones


  Form over warm ocean waters, take a long time to form and gain strength, intensities rated based on wind speeds
• Climate


  An area's general pattern of atmospheric conditions over three decades and longer
• Factors that determine regional climates

  • The cyclical movement of air driven by solar energy and convection
  • Uneven heating of the earth's surface by the sun
  • Tilt of the earth's axis and resulting seasonal changes
  • Rotation of the earth on its axis, creating the Coriolis Effect
  • Ocean currents that redistribute heat from the sun
• Greenhouse gases


  H2O, CO2, CH4, N2O
• Natural greenhouse effect


  Gases keep the earth habitable
• Rain shadow effect


  Most precipitation falls on the windward side of mountain ranges, deserts form on the leeward side
• Heat islands


  Cities create microclimates
• Biomes


  Large terrestrial regions characterized by different types of climate and plant life
• Biomes


  • Tropical deserts
  • Temperate deserts
  • Cold deserts
• Desert ecosystems


  • Slow plant growth and low species diversity
  • Slow nutrient cycling
• Desert


  Annual precipitation low and scattered unevenly throughout the year
• Types of deserts


  • Tropical deserts
  • Temperate deserts
  • Cold deserts
• Desert ecosystems


  • Slow plant growth and low species diversity
  • Slow nutrient cycling
• Grasslands


  Exist in continent interiors, areas too moist for deserts but too dry for forests
• Types of grasslands


  • Tropical
  • Temperate
  • Cold (arctic tundra)
• Tropical grasslands (savannas)


  • Warm temperatures year-round
  • Grazing and browsing animals
• Temperate grasslands


  • Cold winters and hot, dry summers
  • Tallgrass prairies
  • Short-grass prairies
  • Often converted to farmland
• Arctic tundra


  • Plants close to ground to conserve heat
  • Most growth in short summer
  • Animals have thick fur
  • Permafrost (frozen underground soil)
• Alpine tundra


  Above tree line in mountains
• Chaparral


  Dry temperate biome with dense growths of low growing, evergreen shrubs and some small trees with leathery leaves
• Chaparral


  • Thin soil
  • Adapted to and maintained by occasional fires
• Types of forests


  • Tropical
  • Temperate
  • Cold (northern coniferous and boreal)
• Tropical rain forests


  • Hot, high moisture air
  • Stratification of specialized plant and animal niches
  • Rapid recycling of scarce soil nutrients
• What is the impact of human activities in the rain forest
• Temperate deciduous forests


  • Cooler temperatures, abundant moisture
  • Broadleaf deciduous trees
  • Slow rate of decomposition
• What is the impact of human activities on temperate forests
• Coastal coniferous forest


  Also called temperate rain forests, found in scattered coastal regions, ample rainfall and moisture from fog, evergreen coniferous trees
• Cold (northern) coniferous forest

  Also called boreal forests or taigas, south of arctic tundra, cold winters and short summers
• Active Learning: Resource


  1. Research the average temperature and precipitation of a city

  2. Create a climate graph

  3. Hypothesize what kind of biome is there