The Water Cycle, Weather Patterns & Global Systems

The Water Cycle & Energy

  • Key Concepts:

    • The water cycle is driven by two main forces: solar energy and gravity.

    • Solar Energy (Thermal Transfer):

    • The sun provides the energy needed for evaporation, which is the process by which water changes from liquid to gas.

    • Gravity:

    • This force pulls water back down to Earth through precipitation (including rain, snow, etc.) and facilitates its movement across the land as runoff.

    • Condensation:

    • This process occurs when water vapor in the air cools and converts back into liquid droplets, leading to the formation of clouds.

  • Review Questions:

    1. Which process in the water cycle directly supports the claim that the sun is a driving force?

    2. Identify two processes in the water cycle that are driven by gravity.

    3. Identify the processes in the water cycle on the diagram below.

Weather Systems & Air Pressure

  • Key Concepts:

    • Weather is significantly influenced by air pressure and geographic features.

    • Air Pressure:

    • Air naturally moves from areas of high pressure to low pressure. High pressure areas (denoted as "H" on a weather map) typically lead to clear skies, while low pressure areas (denoted as "L") are often associated with stormy weather.

    • The Rain Shadow Effect:

    • When moist air from an ocean encounters a mountain range (for example, the Sierra Nevada), it is pushed upward.

      • As the air ascends, it cools and condenses, resulting in heavy precipitation on the windward (ocean-facing) side of the mountain.

      • Conversely, the leeward side remains considerably drier due to this precipitation.

  • Review Questions:

    1. In which direction does air move?

    2. What happens to warm, moist air as it is pushed higher into the atmosphere by a mountain?

Global Patterns & The Coriolis Effect

  • Key Concepts:

    • The Earth’s rotation establishes large-scale patterns in both the atmosphere and oceans.

    • The Coriolis Effect:

    • Due to the rotational speed variance of the Earth (faster at the equator than at the poles), objects that are not fixed to the surface, like wind and water, appear to curve as they move.

    • Hemisphere Rules:

      • Winds and objects deflect to the RIGHT in the Northern Hemisphere, and to the LEFT in the Southern Hemisphere.

    • Weather Impact:

    • The Coriolis Effect is responsible for the development of "cyclonic" systems, such as hurricanes in the Northern Hemisphere and typhoons in the Southern Hemisphere.

  • Review Questions:

    1. How does the Coriolis Effect impact global weather patterns and wind direction?

    2. In which direction are winds deflected in the Northern Hemisphere due to the Coriolis Effect?

Vocabulary Review

The Water Cycle & Energy

  • Solar Energy:

    • Radiation from the sun that provides the thermal energy essential for powering the water cycle.

  • Evaporation:

    • The process whereby liquid water is heated, transforming it into water vapor (gas).

  • Condensation:

    • The process through which water vapor cools down and reverts back to liquid water droplets, resulting in cloud formation.

  • Precipitation:

    • Any type of water (e.g., rain, snow, sleet, or hail) that descends from clouds and reaches the Earth's surface due to the force of gravity.

  • Transpiration:

    • The process by which plants emit water vapor into the atmosphere through their leaves.

  • Runoff:

    • Water from precipitation that traverses over the land surface, draining into rivers, lakes, and oceans rather than being absorbed into the ground.

Atmosphere & Weather Patterns

  • Air Pressure:

    • The force that results from the weight of air molecules pressing down on a given area.

  • High Pressure (H):

    • An area where air is decreasing in altitude and dispersing, generally leading to clear skies and favorable weather conditions.

  • Low Pressure (L):

    • An area characterized by rising and cooling air, typically associated with cloud formation, wind activity, and precipitation.

  • Air Mass:

    • A significant body of air that possesses uniform temperature and moisture characteristics throughout.

  • Windward Side:

    • The portion of a mountain that is facing the incoming wind, which receives a substantial amount of moisture and precipitation.

  • Leeward Side:

    • The section of a mountain that is shielded from the wind (the "rain shadow") and experiences significantly lower moisture levels.

Global Systems

  • Coriolis Effect:

    • The phenomenon causing the deflection of moving objects (such as wind and ocean currents) to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, attributable to the Earth's rotation.

  • Convection:

    • The process of heat transfer through fluid movement (in both liquids and gases), where warmer, less dense materials rise while cooler, denser materials sink.

  • Global Winds:

    • The extensive wind patterns (including Trade Winds and Westerlies) that redistribute heat and moisture across the planet.