Atmospheric Conditions
Composition
- 78% nitrogen, 21% oxygen, 1% trace gasses (argon, carbon dioxide, other)
- Water vapor, varying 0-5% by volume is responsible for major changes in weather
Layers of the Atmosphere
Exosphere
Outer layer
Thermosphere
280,000’ - 1,848,000’
Mesosphere
160,000’ - 280,000’
small to no effect on weather
Stratosphere
36,000’ - 160,000’
stable
Troposphere
SFC - 36,000’
Contains most of weather/storms
20-60k feet at poles, 48k feet at equator
Pressure & Stability
Pressure
Atmospheric air pressure
Standard Pressure
29.92 inHg
Pressure Lapse Rate
1”Hg per 1,000’ gain (to 10,000’)
Stability
The atmosphere’s resistance to vertical motion
Stable Air
- Limited vertical motion, sinking air
- Smooth air, less cloud development
- Visibility limited by fog, haze, smoke
Unstable Air
- Vertical motion, rising air
- Turbulent air, cloud development
- Good visibility
Standard Temperature
+15º C
Temperature Lapse Rate
2ºC per 1,000’ gain (to 36,000’)
Lifting Mechanisms
Convergence
Divergence
Orographic
Frontal
Convective
Wind
Coriolis Force
Wind Shear
Low Level Wind Shear (LLWS)
Airspeed fluctuations during low-speed phases of flight (takeoff and landing) can cause an airplane to stall
Temperature
Mositure & Dew Point
Clouds
Fog
Visibility
Obstructions to Visibility
Turbulence
- Wake
- Thermal
- Mechanical
- Frontal
- Clear Air
- Mountain Wave
- Thunderstorm