Chapter 6 Flashcards
Definition: Atmospheric Stability
The tendency of the atmosphere to resist or enhance vertical motion.
Stable Atmosphere
Air resists vertical movement, producing slow vertical speeds and steady weather.
Unstable Atmosphere
Air moves upward rapidly, leading to severe weather and thunderstorms.
Lapse Rate
The rate at which temperature decreases with height.
Positive Lapse Rate
Temperature decreases with height (normal condition).
Negative Lapse Rate
Temperature increases with height (temperature inversion).
Dry Adiabatic Lapse Rate (DALR)
Rate of cooling for unsaturated air: ~10°C per km.
Moist Adiabatic Lapse Rate (MALR)
Rate of cooling for saturated air: ~6°C per km.
Environmental Lapse Rate (ELR)
The actual rate at which temperature changes with altitude.
Absolutely Stable Atmosphere
ELR < MALR; air resists vertical motion; forms stratiform clouds.
Absolutely Unstable Atmosphere
ELR > DALR; air accelerates upward; leads to thunderstorms.
Conditionally Unstable Atmosphere
MALR < ELR < DALR; stable if unsaturated, unstable if saturated.
Adiabatic Process
Temperature change occurs due to pressure differences without heat exchange.
Lifting Condensation Level (LCL)
Altitude at which rising air reaches saturation and forms clouds.
Equilibrium Level (EL)
The altitude where rising air stops being warmer than the environment.
Triggers for Rising Air
Surface heating, orographic lifting, surface convergence, frontal lifting.
Orographic Lift
Air forced up by mountains, causing cooling and cloud formation.
Rain Shadow Effect
Leeward side of mountains remains dry due to descending warm air.
Mountain Wave Turbulence
Wave-like disturbances in airflow caused by mountains.
Stabilizing the Atmosphere
Cooling the surface, warming aloft, or cold air advection at the surface.
Destabilizing the Atmosphere
Warming the surface, cooling aloft, or warm air advection at the surface.
Cloud Development
Occurs when air rises, cools, and reaches the dew point.
Stratus Clouds
Form in stable air; spread out horizontally.
Cumulonimbus Clouds
Develop in unstable air; associated with thunderstorms.
Environmental Sounding
Vertical temperature profile measured using weather balloons.
