Weather Changes and Flying Safety

Importance of Understanding Weather for Pilots

• Essential knowledge for ensuring safety during flights.

The Atmosphere

• Definition: Layers of gases surrounding Earth, essential for life.
  • Main gases: Nitrogen, Oxygen, Water Vapor.
• Layers of the Atmosphere: Divided into four main layers.
  • Focus on Troposphere (where most weather occurs).
• Troposphere Characteristics:
  • Thickness varies (4-12 miles at poles; up to 48,000 feet at the equator).
  • Tropopause: Boundary trapping moisture and weather.
• Temperature and Altitude:
  • Temperature decreases by 2°C for every 1,000 feet gain.
• Air Pressure:
  • Air has weight; atmospheric pressure decreases with altitude.
  • Standard pressure at sea level: 29.92 inches of mercury (1,013.2 millibars).
  • Pressure decreases by about 1 inch of mercury for every 1,000 feet.

Influences of the Sun on Weather

• Uneven Heating: Earth’s surface heated unevenly by the sun.
  • Warm air rises; cooler air replaces it, creating circulation.
• Coriolis Force:
  • Affects wind direction due to Earth's rotation.
  • Warm air rises, deflected eastward in the Northern Hemisphere.

Air Pressure Systems

• High Pressure: Cooler, drier air leading to stable weather.
• Low Pressure: Warm air rises, creating unstable weather with potential for clouds and rain.
• Air Movement: Always moves from high pressure to low pressure, influenced by the Coriolis Force.

Weather Charts and Flight Planning

• Using Weather Charts:
  • Use aviationweather.gov for weather conditions and isobar analysis.
  • Closer isobars indicate stronger winds.
• Wind Flags: Indicate wind direction and strength on surface weather charts.

Fronts and Their Characteristics

• Air Masses: Stagnant areas of cool or warm air.
• Fronts:
  • Warm Front: Slow-moving, brings humidity and light rain. Weather before: stratus clouds.
  • Cold Front: Fast-moving, can produce thunderstorms. Weather before: gusty winds and poor visibility.
  • Stationary Front: Mix of a warm and cold front, can cause prolonged bad weather.
  • Occluded Front: Cold front catches up with warm front, can lead to severe weather conditions.

Clouds and Stability

• Types of Clouds:
  • Low clouds: Stratus, Stratocumulus, Nimbostratus.
  • Middle clouds: Altostratus, Altocumulus.
  • High clouds: Cirrus, Cirrostratus, Cirrocumulus.
• Cloud Formation: Depends on temperature, moisture, and stability.
• Stability: Affects weather; unstable air leads to violent weather.

Moisture in the Atmosphere

• Adding Moisture: Primarily through evaporation and sublimation.
• Relative Humidity: Important for understanding weather and cloud formation.

Conclusion

• Understanding stability and moisture levels is crucial for anticipating weather conditions.
• Awareness of weather influences can aid pilots in safe flight planning.