Atmospheric Stability

​Atmospheric Stability

Atmospheric stability is defined as the resistance of the atmosphere to vertical motion.

Unstable atmosphere allows an upward or downward disturbance to grow into a vertical (convective) current. Think thunderstorm development and towering cumulus clouds.

Unstable air can often result in weather conditions unfavorable to sUAS operations. Warming from below, such as the sun shining on pavement or rock, could cause unsta­bility of an air mass.

A stable atmo­sphere resists any upward or downward movement.
A stable layer of air would be associated with a temperature inversion (a condition in which warm air is situated above cool or cold air).

Determining the stability of the atmosphere requires measuring the difference between the actual existing (ambient) temperature lapse rate of a given parcel of air and the dry adiabatic (3°C per 1,000 feet) lapse rate. Because sUAS operate at low

altitudes, it may seem as though lapse rate may not be a factor, but the stability of the local air mass can have significant impact on ambient conditions. Unstable air can often result in weather conditions unfavorable to sUAS operations.

​Atmospheric Stability

Atmospheric stability is defined as the resistance of the atmosphere to vertical motion.

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stability is defined as the resistance of the atmosphere to vertical motion.

​Unstable Atmosphere

Unstable atmosphere allows an upward or downward disturbance to grow into a vertical (convective) current. Think thunderstorm development and towering cumulus clouds.

Unstable air can often result in weather conditions unfavorable to sUAS operations. Warming from below, such as the sun shining on pavement or rock, could cause unsta­bility of an air mass.

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​

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atmosphere allows an upward or downward disturbance to grow into a vertical (convective) current..

​Atmospheric Stability

Unstable Air

Cumuliform clouds

Showery precipitation

Turbulent air

Good visibility

Stable Air

Stratiform clouds

Fog

Steady rain fall

Smooth air

Poor visbility, haze, smoke

Multiple Choice

Can you list some characteristics of stable air?

• Poor visibility and intermittent precipitation.

• Good visibility and steady precipitation.

• Poor visibility and steady precipitation.

​Atmospheric Stability

Unstable Air

Cumuliform clouds

Showery precipitation

Turbulent air

Good visibility

Stable Air

Stratiform clouds

Fog

Steady rain fall

Smooth air

Poor visbility, haze, smoke

​Atmospheric Stability

Weather forecasts often refer to either rain or showers, but did you know they often give a very different 'feel' to the day?

Showers imply the weather will change a lot during the day with rain on and off.

Whereas rain will bring continuous wet weather for hours at a time, and then it will clear.

Categorize

Options (10)

Cumuliform clouds

Stratiform clouds

Showery precipitation

Continuous precipitation

Rough Air

Smooth Air

Good Visibility

Poor Visibility

Fog

No Fog

Organize these options into the right categories

Unstable Air

Stable Air

​Stable Atmosphere

A stable atmo­sphere resists any upward or downward movement.

A stable layer of air would be associated with a temperature inversion (a condition in which warm air is situated above cool or cold air).

​Stable Air
Stratiform clouds
Fog
Steady rain fall
Smooth air
Poor visbility, haze, smoke

Multiple Choice

A stable air mass is most likely to have which characteristic?

• Showery precipitation.

• Turbulent air.

• Poor surface visibility.

​Unstable Atmosphere

Unstable atmosphere allows an upward or downward disturbance to grow into a vertical (convective) current. Think thunderstorm development and towering cumulus clouds.

Unstable air can often result in weather conditions unfavorable to sUAS operations. Warming from below, such as the sun shining on pavement or rock, could cause unsta­bility of an air mass.

Multiple Choice

What are characteristics of a moist, unstable air mass?

• Turbulence and showery precipitation

• Poor visibility and smooth air.

• Haze and smoke.

​Stable Atmosphere

A stable atmo­sphere resists any upward or downward movement.

A stable layer of air would be associated with a temperature inversion (a condition in which warm air is situated above cool or cold air).

​Stable Air
Stratiform clouds
Fog
Steady rain fall
Smooth air
Poor visbility, haze, smoke

Multiple Choice

What are characteristics of stable air?

• Good visibility and steady precipitation.

• Poor visibility and steady precipitation.

• Poor visibility and intermittent precipitation.

​Temperature Lapse Rate

Determining the stability of the atmosphere requires measuring the difference between the actual existing (ambient) temperature lapse rate of a given parcel of air and the dry adiabatic (3°C per 1,000 feet) lapse rate. Because sUAS operate at low

altitudes, it may seem as though lapse rate may not be a factor, but the stability of the local air mass can have significant impact on ambient conditions. Unstable air can often result in weather conditions unfavorable to sUAS operations.

Multiple Choice

What measurement can be used to determine the stability of the atmosphere?

• Atmospheric pressure.

• Actual lapse rate.

• Surface temperature.

Explanation Slide...

When air near the surface is warm and moist, suspect instability. Surface heating, cooling aloft, converging or upslope winds, or an invading mass of colder air may lead to instability nd cumuliform clouds

Multiple Choice

What would decrease the stability of an air mass?

• Warming from below.

• Cooling from below.

• Decrease in water vapor.

Explanation Slide...

Unstable conditions are characterized by cumulus clouds, turbulence, showery precipitation, and good visibility

Multiple Choice

Upon your preflight evaluation of weather, the forecasts you reference state there is an unstable air mass approaching your location. Which would not be a concern for your impending operation?

• Thunderstorms.

• Stratiform clouds.

• Turbulent conditions.

​low-level temperature inversion - Smooth Air

A "low-level temperature inversion with high relative humidity" means you should anticipate foggy or misty conditions near the ground, potentially impacting visibility, as a layer of warmer air traps cooler air near the surface, and the high humidity allows for more moisture to condense into fog. 

Key points about this weather scenario:

• Temperature inversion: This is a situation where a layer of warmer air sits above a layer of cooler air, which is the opposite of the usual temperature decrease with altitude. 

• Low-level: The inversion is occurring close to the ground. 

• High relative humidity: The air is near saturation with moisture, which increases the potential for fog formation. 

What to expect:

• Fog: Dense fog patches or widespread low visibility, especially in the early morning or late evening hours.

• Reduced visibility: Difficulty seeing objects at a distance.

• Potential for icing: If temperatures are near freezing, fog droplets can freeze on surfaces.

• Air pollution trapping: Inversions can trap pollutants close to the ground, leading to poor air quality.

Multiple Choice

You have received an outlook briefing from flight service through 1BOOwxbrief.com.The briefing indicates you can expect a low-level temperature inversion with high relative humidity. What weather conditions would you expect?

• Smooth air, poor visibility, fog, haze, or low clouds.

• Light wind shear, poor visibility, haze, and light

  rain.

• Turbulent air, poor visibility, fog, low stratus type clouds, and showery precipitation.