Topic 9: Earth's Climatic Regions

Topic 9: Earth's Climatic Regions

Overview of Topics

  • Weather vs. Climate

  • Controls on Climate

  • Global Classification of Climates
      - Tropical Climates
      - Mesothermal Climates
      - Microthermal Climates
      - Polar Climates
      - Arid and Semiarid Climates

  • GEOG 203: Planet Earth

Weather vs. Climate

  • Weather
      - Short-term atmospheric conditions which include:
        - Temperature
        - Humidity
        - Cloudiness
        - Precipitation
        - Pressure
        - Winds

  • Climate
      - Refers to the average weather conditions measured over a long period of time, commonly referred to as climate “normals.”
      - Determined by:
        - Temperature
        - Precipitation
      - Vital for understanding the global distribution of ecosystems (biomes).

Earth's Climatic Classification

  • The classification of climates is based on several climate components, which include:
      - Insolation/Latitude
      - Temperature
      - Pressure
      - Air masses
      - Precipitation

Principal Temperature Controls

  1. Latitude
       - Determines the amount of solar radiation received at different locations on Earth.

  2. Altitude
       - Higher altitudes typically have cooler temperatures.

  3. Cloud Cover
       - Influences local temperatures by affecting the amount of sunlight reaching the surface.

  4. Land/water Distribution
       - Land heats up and cools down faster than water, affecting local climates.

Precipitation Mechanisms

  • There are four primary precipitation mechanisms:
      1. Convergent Lifting
      2. Convectional Lifting
      3. Orographic Lifting
      4. Frontal Lifting

Understanding Precipitation

  • General Observations:
      - Equatorial Region
        - Characterized by high wetness due to the convergence of trade winds, extensive convection (heating), and abundant moisture.
      - Subtropics
        - Typically dry due to the presence of descending air from Hadley cells, which creates areas of high pressure.
      - Mountain Regions
        - Exhibits variable climates.
          - Windward Side: Wet climate
          - Leeward Side: Dry climate
      - Continental Interiors
        - Generally dry due to the distance from moisture sources.

Types of Temporal Precipitation Patterns

  1. Uniform Pattern:
       - All months receive approximately equal amounts of precipitation.

  2. Summer Maximum Pattern

  3. Winter Maximum Pattern

  4. Double Maxima:
       - Example includes spring and fall precipitation.

Guess the Region - Example Data

  • Region Characteristics:
      - Mean precipitation = 2971 mm (115 in.)
      - Mean Annual Temperature = 25°C (77°F)
      - A represented tropical rainforest.

  • Second Region Characteristics:
      - Mean precipitation = 450 mm (18 in.)
      - Mean Annual Temperature = 20°C (68°F)
      - A represented low-latitude hot steppe.

Idealized Global Climates

  • Climatic Relationships
      - Cold
        - Polar ice sheet, tundra, taiga, cool summer, etc.
      - Warm to hot
        - Desert, humid subtropical, tropical, etc.

Climate Classifications

  1. Genetic Classifications:
       - Based on forcing factors such as:
         - Net radiation
         - Thermal regime
         - Air masses

  2. Empirical Classification:
       - Based on actual data such as:
         - Temperature
         - Precipitation

The Five Climate Regions of the World

A. Tropical (3 subtypes)
B. Mesothermal (mild winter) (3 subtypes)
C. Microthermal (cold winter) (4 subtypes)
D. Polar & Highland (2 subtypes)
E. Desert (2 subtypes)

Tropical Climates

  • Defined by geographic boundaries between the Tropic of Cancer and the Tropic of Capricorn.
      - Experience consistent insolation and daylength resulting in consistently warm temperatures and no winters.
      - Rainfall is determined largely by the Intertropical Convergence Zone (ITCZ) with year-round moisture surplus.
      - Warm oceans contribute to an unstable atmosphere conducive to precipitation.

Subtypes of Tropical Climates

  1. Tropical Rainforest:
       - Constantly wet with significant water surpluses.

  2. Tropical Monsoon:
       - Seasonal reversal of winds, with at least one dry month.

  3. Tropical Savanna:
       - Distinct wet and dry seasons of equal length.

Mesothermal Climates

  • Midlatitude climates characterized by mild winters and true seasonality.
      - Regions are influenced by changing air masses (mT, cP) and midlatitude wave cyclones.
      - Significant differences between west coast and east coast climates as temperatures decrease poleward.

Subtypes of Mesothermal Climates

  1. Humid Subtropical:
       - Consistently moist throughout the year (example: Texas).

  2. Marine West Coast:
       - Year-round moisture with mild winters (due to mP air masses).

  3. Mediterranean:
       - Characterized by dry summers, often influenced by subtropical highs or cold ocean currents.

Microthermal Climates

  • Found in middle and high latitudes, defined by:
      - Temperature:
        - Cold and long winters; hot (or cool) summers depending on latitude.
      - Moisture:
        - Availability is year-round, with exceptions in small monsoon regions.
      - Note: No microthermal climates exist in the Southern Hemisphere!

Subtypes of Microthermal Climates

  1. Humid Continental:
       - Varying from hot summers (like the U.S. Midwest) to mild summers.

  2. Subarctic:
       - Cool summers (boreal forest) and very cold winters (e.g., Siberia).

Polar and Highland Climates

  • General characteristics:
      - No true summer; even during long daylight hours, temperatures are typically below 10°C (50°F).
      - Conditions too extreme for tree growth.
      - Extremely low moisture levels lead to designs described as “frozen deserts.”

Subtypes of Polar and Highland Climates

  1. Tundra:
       - Features summers barely above freezing with permafrost.

  2. Ice Cap:
       - Remains below freezing year-round (i.e., Greenland & Antarctica).

Desert (Arid and Semiarid) Climates

  • The most extensive climate region characterized by a moisture demand (POTET) that exceeds moisture supply (PRECIP), resulting in a constant deficit.
      - Influencing factors include:
        - Subtropical highs
        - Cold ocean currents
        - Rain shadow effects
        - Great distances from ocean moisture sources.

Subtypes of Desert Climates

  1. Arid Desert:
       - Example: Riyadh, Saudi Arabia.

  2. Semi-Arid Steppe:
       - Example: Walgett, Australia.

Climate Classification Summary: Global Perspective

  • Climates can be classified into three broad types:
      - Tropical Climates:
        - Include tropical rainforests, monsoons, and savannas.
      - Desert Climates:
        - Comprise arid and semiarid regions across various latitudes.
      - Mesothermal and Microthermal Climates:
        - Include humid subtropical, marine west coast, Mediterranean, humid continental, and subarctic climates.
      - Polar and Highland Climates:
        - Represent extreme, cold environments like tundras and ice caps.

These notes reflect comprehensive details regarding the climate types, their implications, and key characteristics discussed throughout the lecture series in GEOG 203: Planet Earth.