Earth's Water Cycle and Atmosphere

Evaporation

• The process of a liquid (water) changing into a gas (water vapor)
• Occurs when the temperature and humidity of the air are suitable
• Factors that influence evaporation:
  • Temperature: Higher temperatures increase evaporation rate
  • Humidity: Lower humidity increases evaporation rate
  • Wind: Increased wind speed increases evaporation rate
  • Surface area: Larger surface area increases evaporation rate

Condensation

• The process of a gas (water vapor) changing into a liquid (water)
• Occurs when the air reaches its dew point (the temperature at which the air becomes saturated with water vapor)
• Factors that influence condensation:
  • Temperature: Lower temperatures increase condensation rate
  • Humidity: Higher humidity increases condensation rate
  • Presence of condensation nuclei (e.g. dust, salt)

Water Cycle

• The continuous process by which water is circulated between the Earth and the atmosphere
• Consists of three main stages:
  1. Evaporation: Water is evaporated from the Earth's surface into the atmosphere
  2. Condensation: Water vapor in the atmosphere condenses into clouds
  3. Precipitation: Water from clouds falls back to the Earth's surface
• Other stages: Runoff, infiltration, and transpiration

Precipitation

• The formation of water droplets in the atmosphere that fall to the Earth's surface
• Types of precipitation:
  • Rain: Liquid droplets
  • Snow: Ice crystals
  • Sleet: Rain droplets that freeze before reaching the ground
  • Hail: Upward-moving water droplets that freeze into ice balls
• Factors that influence precipitation:
  • Temperature: Cooler temperatures increase precipitation
  • Humidity: Higher humidity increases precipitation
  • Wind: Wind direction and speed influence precipitation patterns

Atmospheric Pressure

• The pressure exerted by the weight of the air in the atmosphere
• Measured in units of pressure (e.g. millibars, inches of mercury)
• Factors that influence atmospheric pressure:
  • Temperature: Higher temperatures decrease atmospheric pressure
  • Humidity: Higher humidity decreases atmospheric pressure
  • Altitude: Higher altitudes decrease atmospheric pressure
• High and low-pressure systems:
  • High pressure: Associated with fair weather and sinking air
  • Low pressure: Associated with bad weather and rising air