ATPL Meteorology - Class 6: Clouds.

Summary

This meteorology class explores cloud formation, starting with the basics of condensation and the dew point. It explains how clouds form from air cooling and water vapor condensing, influenced by dry and saturated adiabatic lapse rates. The video covers various cloud types, from high-level cirrus to low-level cumulonimbus, and their association with weather conditions. It also discusses cloud stability, the environmental lapse rate, and how these factors affect cloud cover and visibility for pilots, concluding with the significance of cloud classification in weather reports.

Takeaways

• 🌧️ Clouds form due to the process of condensation, where water vapor cools and changes from a gas to a liquid state.
• 🌡️ The dew point is the temperature at which air reaches saturation and water vapor starts to condense.
• 🧊 If the dew point is below freezing, water vapor can sublimate directly into ice crystals, forming around impurities or remaining as supercooled droplets until an impurity is introduced.
• 🌬️ Adiabatic cooling occurs when air expands and cools due to a drop in pressure, separate from the cooling caused by the surface temperature.
• ⬆️ As air rises, it cools at a rate of 3 degrees per thousand feet (dry adiabatic lapse rate) until it reaches the dew point, after which it cools at 1.8 degrees per thousand feet (saturated adiabatic lapse rate).
• 🌫️ Fog and mist are forms of low clouds that form when air is cooled near the surface, rather than through adiabatic rising.
• 🏞️ Air rises due to being warmer, orographic lifting by geographic features, or when encountering a front of colder, denser air.
• 🌟 Stability of air is determined by comparing the environmental lapse rate to the adiabatic lapse rates, which affects whether air will continue to rise, sink, or remain stable.
• 🌦️ Clouds are categorized by their stability (stable or unstable), height (low, mid, high), shape (stratiform or cumuliform), and the type of precipitation they produce.
• 📊 Cloud cover at aerodromes is reported in 'oktas', with full coverage being overcast and clear skies reported as 'SKC'.

Q & A

What is the fundamental concept behind cloud formation?

The fundamental concept behind cloud formation is condensation, which is the process of water vapor cooling to the point where it changes from a gas to a liquid state.

What is the dew point and how does it relate to cloud formation?

The dew point is the temperature at which the saturation vapor pressure matches the actual amount of water vapor in the air, leading to condensation. This is where water vapor starts to condense, marking the beginning of cloud formation.

How does the temperature change as air rises and its effect on cloud formation?

As air rises, the pressure drops, causing the air to expand and cool. This cooling is known as adiabatic cooling, which occurs at a rate of 3 degrees per thousand feet for dry air and 1.8 degrees per thousand feet for saturated air, influencing cloud formation.

What is the difference between dry and saturated adiabatic lapse rates?

The dry adiabatic lapse rate is 3 degrees per thousand feet and occurs when the air is not saturated, while the saturated adiabatic lapse rate is 1.8 degrees per thousand feet and occurs when the air is saturated and water vapor starts to condense.

Why do clouds form at different altitudes?

Clouds form at different altitudes based on the temperature and dew point. The altitude at which the air cools to the dew point determines the cloud base, with different types of clouds forming at low, mid, and high levels.

What role do impurities play in the formation of ice crystals in clouds?

Impurities in the air, such as smog particles or dust, provide a surface for ice crystals to form when the temperature is below freezing. Without impurities, supercooled water droplets may form and only freeze when they encounter an impurity.

How does the environmental lapse rate affect the stability of the atmosphere and cloud formation?

The environmental lapse rate compares to the adiabatic lapse rates to determine atmospheric stability. If it's lower than both dry and saturated adiabatic lapse rates, the atmosphere is stable, but if it's higher, the atmosphere is unstable, leading to more cloud formation.

What are the two broad categories of clouds and how do they differ?

The two broad categories of clouds are stable and unstable. Stable clouds are widespread and low, associated with light precipitation, while unstable clouds are tall and fluffy, associated with heavier showers and turbulence.

How are clouds classified by height and what are the categories?

Clouds are classified by height into low-level clouds (up to 6,500 feet), mid-level clouds (6,500 to 23,000 feet), and high-level clouds (above 23,000 feet).

What does it mean when clouds are described in terms of 'octas' in aviation?

In aviation, clouds are described in terms of 'octas' or eighths to indicate the amount of sky covered by clouds overhead an aerodrome, ranging from clear sky to overcast.