Sub-topic 3: Clouds, Precipitation, and Visibility
Understanding clouds, precipitation, and visibility is crucial for safe and efficient aviation. This module delves into the formation, types, and associated weather phenomena that pilots must be aware of.
Cloud Formation and Types
Clouds are visible masses of water droplets or ice crystals suspended in the atmosphere. They form when air cools to its dew point, causing water vapor to condense. The altitude and atmospheric conditions determine the type of cloud that forms.
High, Middle, and Low.
Precipitation
Precipitation is any form of water that falls from clouds and reaches the ground. The type of precipitation depends on the temperature profile of the atmosphere between the cloud and the ground.
| Precipitation Type | Formation Conditions | Associated Hazards |
|---|---|---|
| Rain | Water droplets that form in clouds and remain liquid until they reach the ground. Occurs when temperatures are above freezing throughout the atmospheric column. | Reduced visibility, hydroplaning on runways. |
| Snow | Ice crystals that form in clouds and remain frozen as they fall. Occurs when temperatures are below freezing throughout the atmospheric column. | Reduced visibility, accumulation on runways and aircraft, icing. |
| Sleet (Ice Pellets) | Rain that freezes as it falls through a layer of sub-freezing air near the surface. Forms when snow melts and then refreezes. | Reduced visibility, slippery surfaces, potential for aircraft icing. |
| Freezing Rain | Rain that falls as liquid but freezes on contact with surfaces that are at or below freezing. Occurs when a warm layer is above a shallow sub-freezing layer near the surface. | Severe icing on aircraft and runways, extremely hazardous conditions. |
| Hail | Lumps of ice that form in strong updrafts within cumulonimbus clouds. Can be carried up and down multiple times, accumulating layers of ice. | Severe structural damage to aircraft, reduced visibility, turbulence. |
Visibility
Visibility is the greatest horizontal distance at which an object can be seen and identified. It is a critical factor for safe flight operations, especially during takeoff, landing, and low-level flight.
This diagram illustrates the process of cloud formation. It begins with the presence of water vapor in the atmosphere. When air rises and cools to its dew point, condensation occurs, forming tiny water droplets or ice crystals. These particles aggregate to form visible clouds. The type of cloud formed depends on factors like altitude, temperature, and atmospheric stability.
Text-based content
Library pages focus on text content
Cumulonimbus clouds are the most dangerous for aviation due to associated thunderstorms, heavy precipitation, hail, lightning, and severe turbulence.
Fog reduces visibility to less than 5/8 statute mile (1000 meters), while mist has visibility greater than or equal to 5/8 statute mile but less than 6 statute miles.
Learning Resources
The official WMO Cloud Atlas provides comprehensive information and images for all cloud types, essential for identification and understanding.
This handbook is a foundational resource for understanding aviation weather, including detailed sections on clouds, precipitation, and visibility.
Provides real-time aviation weather information, including forecasts, current conditions, and graphical products crucial for flight planning.
A clear and concise explanation of cloud types and their formation from the UK's national weather service.
A series of articles tailored for pilots, covering various weather topics including clouds and visibility in an accessible format.
Focuses on the practical implications of different cloud types for pilot decision-making and safety.
Detailed explanation of the formation, types, and forecasting of fog, a critical factor for visibility.
Covers the formation and characteristics of various precipitation types, including rain, snow, sleet, and freezing rain.
A comprehensive wiki-style resource covering a wide range of aviation weather topics, including clouds, visibility, and precipitation.
Explains the importance of visibility for pilots and the various factors that affect it during flight operations.