Climate Classification

• Climate zones


  Largely determined by temperature and precipitation
• Controls on climate


  • Temperature (latitude, altitude, land-water, ocean currents, mountain barriers)
  • Precipitation (air pressure, air mass influences, prevailing winds)
• Principal temperature controls


  • Latitude
  • Altitude
  • Cloud Cover
  • Land/water
• Precipitation mechanisms


  • Convergent Lifting
  • Convectional Lifting
  • Orographic Lifting
  • Frontal Lifting
• Equatorial region


  Wet, due to convergence of trade winds, lots of convection, ample moisture
• Subtropics


  Dry, due to sinking air and Hadley cells producing high pressure
• Mountain regions


  Variable, wet on windward side, dry on leeward side
• Continental interiors


  Dry, far away from moisture sources
• Types of temporal precipitation patterns

  • Uniform
  • Summer max
  • Winter max
  • Double maxima
• Major controls of climate

  • Latitude
  • Land/water influence
  • Geographic position and prevailing winds
  • Mountains and highlands
  • Ocean currents
  • Pressure and wind systems
• Köppen climate classification


  Based on dominant vegetation types, which respond to temperature and precipitation
• Ancient Greeks had a "logic-based" climate classification with 3 regions: Frigid Zone, Temperate Zone, Torrid Zone
• Köppen climate types


  • A: Tropical
  • B: Arid/dry
  • C: Mesothermal (midlatitude mild)
  • D: Microthermal (midlatitude cold)
  • E: Polar
  • H: Highland
• Köppen first-order divisions


  A, C, and D climates support trees, B and E climates are too dry or too cold
• Köppen second-order subdivisions for A, C, and D climates

  • f: wet year-round
  • s: summer dry
  • w: winter dry
  • m: tropical monsoon
• Köppen second-order subdivisions for B (dry) climates

  • S: semi-arid
  • W: true deserts
• Köppen second-order subdivisions for E (polar) climates

  • T: milder, tundra sub-type
  • F: frozen, ice cap sub-type
• Köppen third-order subdivisions for C and D climates


  • a: hot summers
  • b: warm summers
  • c: mild summers
  • d: cool summers
• Köppen third-order subdivisions for B (arid) climates


  • h: hot arid or semi-arid
  • k: cold arid or semi-arid
• Climate classification approaches


  • Genetic (based on forcing factors)
  • Empirical (based on actual data)
• Tropical Rainforest Climate(A)


  Hot and humid, no winter, high rainfall, lush evergreen vegetation
• Tropical Monsoon climate


  Similar to Tropical Rainforest but with a dry season, coastal areas, seasonal reversal of winds
• Tropical Savanna climate


  North/south of tropical rainforests, distinct wet and dry seasons of approximately equal length, greater annual temperature variability
• Mesothermal climates


  Moderate climates with definite seasonal rhythm in temperature, coldest month between -3°C to +18°C, warmest month above +10°C
• Mesothermal climate types


  • Humid Subtropical (hot summer, winter dry)
  • Marine West Coast
  • Mediterranean
• Humid Subtropical climate


  Hot, humid summers and mild, chilly winters, found in southeastern US, southeastern South America, coastal southeast South Africa, eastern Australia, and eastern Asia
• Mesothermal Climates


  • Humid Subtropical
  • Marine West Coast
  • Mediterranean
• Humid Subtropical Climates


  • Hot, humid summers and mild, chilly winters
  • Found in the southeastern United States, southeastern South America, coastal southeast South Africa, eastern Australia, and eastern Asia from northern India through south China to Japan
  • Summer temperatures average between 21°C (69.8°F) to 26°C (78.8°F)
• Humid Subtropical Subtypes


  • Hot-Summer
  • Winter-Dry
• Humid Subtropical Hot-Summer


  • B.1a Humid Subtropical Hot-Summer
  • Moist year-round
  • Summer = convection
  • Winter = frontal lifting
• Humid Subtropical Winter-Dry


  • B.1b Humid Subtropical Winter-Dry
  • Monsoonal moisture
  • Summer = monsoon
  • Winter = dry
• Cherrapunji, India has the world records for highest yearly precipitation (87 feet or 1044 inches) and highest monthly precipitation (30.5 feet or 366 inches)
• Marine West Coast Climates

  • Found in Pacthe ific Northwest (U.S. & Canada) and Northern Europe
  • mP air masses – cool, moist, unstable
  • Year-round moisture
  • Surprisingly mild winters (>0°C), cool summers
  • Dominated by cyclonic activity embedded in the Westerlies
  • Orographic uplift is an important climate control
• Mediterranean Climates

  • Dry summers caused by expansion of subtropical high
  • Winters are (relatively) wet, also caused by cold ocean currents
  • Located on the western coasts of continents, roughly between 30 and 45 degrees north and south of the equator and often with westerly prevailing winds
• Microthermal Climates

  • In middle- and high-latitudes
  • Winters: cold and long
  • Summers: hot (south) to cool (north)
  • Moisture: Year-round, but small monsoon region in Asia = dry winters
  • No microthermal climates in the Southern Hemisphere
• Microthermal Climate Types


  • Humid Continental Hot-Summer
  • Humid Continental Mild-Summer
  • Subarctic Cool Summer
  • Subarctic Very Cold Winter
• Humid Continental Hot-Summer Climates

  • C.1 Humid Continental Hot-Summer
  • Hot summers & moderate winters
  • Found in U.S. Midwest to the northeast and northeast China
  • Moist year-round, with summer convection and winter midlatitude wave cyclones
  • Asia has a monsoonal moisture regime with dry winters
• Subarctic Climates

  • Found in North America (most of Alaska & Canada) and Eurasia (northern Europe, most of Russia)
  • Large temperature seasonality
  • Year-round (low) moisture
  • Extremely cold winters (−90°F), mild summers.
• Polar and Highland Climates

  • No true summer
  • Temperature: Even during 24 hrs of daylight, T<10°C (50°F)
  • Too cold for trees
  • Moisture: Extremely dry—"frozen deserts"
• Tundra Climate

  • Summer barely above freezing
  • 8–10 months of snow-covered ground
  • Low-growing vegetation when snow melts
  • Extensive permafrost.