Ch. 10

Climatic Factors that Impact Communities

1. Definitions

• Weather: Short term fluctuations in:

  • Temperature

  • Humidity

  • Cloud cover

  • Rainfall

  • Influences individual organisms

• Climate: The prevailing/long-term patterns of weather in a specific region.

  • Limits the overall distribution of species.

2. Factors Influencing Earth's Ecosystems

2.1. Climate

• Defined as the long-term pattern of weather in a particular area.

  • Average elements of climate:

    • Average temperature

    • Average rainfall

    • Average solar radiation

    • Humidity

  • Climate further impacted by:

  • Latitude

  • Proximity to large bodies of water

  • Elevation

  • Relationship to major geographic features

2.2. Latitude

2.2.1. Impact of Latitudes on Climate

• Sun's rays hit at a right angle to the surface near the equator.

  • Rays cover a smaller area but carry more energy.

• Near the poles, light hits at a smaller angle:

  • Area covered by the light is larger but energy is the same.

• Result: warm climates at the equator and cold climates at poles.

2.2.2. Seasonal Variation

• Earth’s axial tilt causes hemispheres to experience differing seasons.

• Greater variation between summer and winter as latitude increases.

3. Air Currents

3.1. Generation of Air Currents

• Generated by the Earth’s rotation.

• Resulting from differences in temperature between air masses.

3.2. Properties of Air

• Warm air is less dense than cold air.

• At the equator:

  • Direct sunlight heats the air, allowing it to absorb large amounts of water.

  • As the equatorial air rises, it cools and releases water as precipitation in the tropics.

  • Note: Cold air cannot hold as much water as warm air.

3.3. Climatic Regions Produced by Air Currents

• Various air currents contribute to distinct climatic regions:

  • Doldrums

  • Trade winds

  • Westerlies

  • Polar Easterlies

3.4. Tropospheric Patterns

• The tropics are the warmest and wettest regions on Earth.

• Cooler, dry air flows away from the equator towards 30°N and 30°S, leading to arid regions.

• Patterns continue as one moves further north and south from the equator.

• Directions of air currents affected by the Coriolis Effect.

4. Rainfall

4.1. Factors Determining Rainfall

• Rainfall primarily determined by the interaction of two factors:

  • Temperature

  • Earth’s rotation

• Responsible for broad range of climates observed on Earth.

4.2. Distribution of Rainfall

• Rain falls unevenly, with varying precipitation levels:

  • Some areas experience minimal precipitation.

  • Others receive heavy rain frequently.

5. Ocean Currents

5.1. Oceans as a Major Water Compartment

• Oceans contain 97% of all liquid water on Earth.

• Home to 90% of the Earth's biomass.

• Major role in moderating Earth’s climate.

5.2. Moderating Climate through Oceanic Currents

• Ocean currents, driven by Earth's rotation and solar heating, distribute warm and cold water.

• Example: The North Atlantic Current brings a warm climate to the United Kingdom.

5.3. Effects of Specific Ocean Currents

• Currents affect local and global climates:

  • Transfer heat from tropics to polar regions and vice-versa.

  • Example: The CA current brings cold, nutrient-rich waters to the Pacific Northwest, creating upwellings.

  • Newfoundland vs. UK: similar latitudes but UK has a more moderate climate.

5.4. Gyres and Their Influence

• Gyres: Circular patterns in ocean currents.

• The Gulf Stream impacts the climate of the East Coast of North America and the West Coast of Europe:

  • Moderates northern European climate despite higher latitude.

  • Gulf Stream part of the clockwise-rotating North Atlantic Gyre.

6. Physical Factors Influencing Climate

6.1. Role of Continents and Mountains

• Continents and mountains complicate weather and climate.

• Climate variation occurs due to surface variability:

  • Land masses heat and cool faster than water masses.

6.2. Influence of Elevation

• Elevation impacts temperature and precipitation:

  • Differences in average annual temperature and precipitation based on altitude.

• Example of vertical zonation:

  • Climbing a mountain reveals environmental changes, from warm rainforests at the base to subalpine tundra at the summit.

6.3. Vertical Zonation

• Defined as vegetation zones influenced by altitude:

  • Environment changes with altitude, affecting types of vegetation.

  • Example: Mount Mansfield in Vermont exhibits significant vertical zonation:

  • Peak: 4,393 feet (1,339 m)

  • Base: 1,803 feet (549.6 m)

7. Rain Shadow Effect

7.1. Formation of Rain Shadows

• High mountain peaks can create rain shadows:

  • Rain shadow deserts form on the leeward side of mountains due to elevation.

7.2. Mechanism of Rain Shadow Formation

• Mountains act as cloud formers and rain catchers:

  • Air sweeps up the windward side of a mountain, lowering pressure and cooling.

  • When saturation point is reached, moisture condenses, leading to precipitation.

  • After the peak, cool, dry air descends the leeward side, creating dry conditions.

7.3. Examples of Rain Shadow Effects

• Mt. Waialeale (Hawaii):

  • Windward side receives 11.8 meters of rain per year.

  • Leeward side receives only 0.46 meters per year.

• Death Valley (California):

  • Rain shadow effect noted, situated on the leeward side of the Sierra Nevada mountains, experiencing extremely low precipitation overall.