Module 3, Lesson 4 - Clouds and Precipitation

Module 3, Lesson 4 - Clouds and Precipitation

Clouds and Precipitation 

A cloud is a conglomeration of minuscule water droplets or ice crystals suspended in the atmosphere. Remote pilots should maintain a safe distance from them. 

There are two classifications of clouds:

• Stratus clouds are gray and layered in appearance, typically covering the entire sky.

• Cumulus clouds are distinct and puffy, they are more vertically developed and often appear like cotton balls in the sky with flat bases

When precipitation falls from either of these cloud forms, nimbus is associated with the name.

Stratus Cloud

Forms in stable air and may produce a light mist or drizzle.

Stratocumulus Cloud

Possess characteristics of both stratus and cumulus clouds and often appears as closely spaced clusters or rolls of clouds, with clear sky in between.

Nimbostratus Cloud

Thicker and darker than, but similar in form to a stratus cloud.

Cumulus Cloud

In the absence of extensive vertical development, is typically associated with fair weather.

Cumulonimbus Cloud

Developed in an unstable environment aloft and can extend to vast altitude.

Cumuliform Cloud

Often follows the diurnal cycle of solar heating

Multiple Select

What may accompany precipitation falling from this type of cloud? (Select all that apply)

• Lightning

• Hail

• Snow

• Thunder

Observing the movement of clouds can provide insight into the direction and speed of the wind at that level. 

Multiple Choice

Forecasts often give a description of the sky condition, including a cloud ceiling, which will tell remote pilots the height of the lowest cloud above ground level described as either broken or overcast. This is important because remote pilots must maintain a minimum clearance of ______ feet below a cloud and ______ feet horizontally from any cloud.

• 500, 2000

• 400, 1000

• 2000, 500

• 1000, 400

Dew point is the approximate temperature to which water vapor in the air must be cooled and can be used in the prediction of cloud formation. The base of the cloud deck for non-precipitating clouds can be well estimated by calculating the dew point depression. 

At the surface calculate:

• Air temperature- dew point temperature = Dew Point Depression

• Double the difference and add two zeros for an estimating of the cloud base.  

Multiple Choice

What is the dew point depression and cloud base when the temperature is 50 F with a dew point of 40 F?

• 10 F dew point depression and 2000 ft. cloud base

• 10 F dew point depression and 20 ft. cloud base

• 20 F dew point depression and 200 ft. cloud base

• 20 F dew point and 20 ft. cloud base

Fog is a stratiform cloud residing at ground level which occurs when the difference between the air temperature and dew point is small. Fog reduces visibility significantly.

Multiple Choice

Radiation fog

• Forms when near-surface air is moved horizontally over a cooler underlying surface

• Formed when the underlying surface that cool air is flowing over is sufficiently cold

• Occurs when warm rain falls into a layer of cold and moist air

• Brought about by cooling the air adjacent to the ground

• The air mass become saturated when a warm and moist underlying surface evaporates

Multiple Choice

Advection Fog

• The air mass become saturated when a warm and moist underlying surface evaporates

• Formed when the underlying surface that cool air is flowing over is sufficiently cold

• Brought about by cooling the air adjacent to the ground

• Occurs when warm rain falls into a layer of cold and moist air

• Forms when near-surface air is moved horizontally over a cooler underlying surface

Multiple Choice

Ice fog

• The air mass become saturated when a warm and moist underlying surface evaporates

• Formed when the underlying surface that cool air is flowing over is sufficiently cold

• Brought about by cooling the air adjacent to the ground

• Occurs when warm rain falls into a layer of cold and moist air

• Forms when near-surface air is moved horizontally over a cooler underlying surface

Multiple Choice

Evaporation/Steam fog

• The air mass become saturated when a warm and moist underlying surface evaporates

• Formed when the underlying surface that cool air is flowing over is sufficiently cold

• Brought about by cooling the air adjacent to the ground

• Occurs when warm rain falls into a layer of cold and moist air

• Forms when near-surface air is moved horizontally over a cooler underlying surface

Multiple Choice

Frontal fog

• The air mass become saturated when a warm and moist underlying surface evaporates

• Formed when the underlying surface that cool air is flowing over is sufficiently cold

• Brought about by cooling the air adjacent to the ground

• Occurs when warm rain falls into a layer of cold and moist air

• Forms when near-surface air is moved horizontally over a cooler underlying surface

REMEMBER: A visibility of at least 3 SM is required throughout the

duration of flight operations.

Multiple Choice

If a remote pilot or visual observer cannot identify objects at a known distance or at distances marked on a map, what should the remote pilot do?

• Make sure it's a clear day with good visibility so they can avoid the objects

• Estimate their distance and try to avoid them

• Not conduct flight operations