Clouds, Fog, Precipitation

Clouds

There are different types of clouds (shapes, altitudes), and some of these clouds can either be easier or challenging for pilots to contend with during flight. 

Cloud height: temperature multiplied by dew point = in feet 


Clouds: formed by air being cooled to its dew point


Cirrus: high clouds - a line of them approaching indicates a warm front.


Alto Clouds: mid level clouds


Cumulus Cloud: created by unstable air (fast moving), lots of vertical turbulence, better visibility, intense but brief rains, gusty conditions, requires more battery to fly properly, low clouds


Stratus Cloud: created by stable air (limited speed), form in layers, have stable flying conditions, long rains/drizzles, steady winds

Image Source: https://www.almanac.com/cloud-guide-types-clouds-and-weather-they-predict

Stratocumulus: mixture of Stratus and Cumulus, drizzle, instability, low visibility, turbulence, showers, poor flying condition

Cumulonimbus: 20,000 feet or higher, instability, low clouds, turbulence, showers. Hazardous to flight. 


Cirro cumulus and Cirrostratus: 20, 000 feet or higher, instability. 


Alto Cumulus: instability, good visibility, showers, turbulence 


Altostratus: drizzle, limited visibility, smooth air, stability, continuous precipitation 


Towering Cumulus: 20,000 feet or higher, instability, good visibility, showers, low clouds, turbulence

Fog

There are many types of fog; some can interfere with visibility of an aircraft (or a pilot's vision) and some can affect an aircraft physically.

Fog: surface air cloud - there are 6 different types: radiation, advection, upslope, ice/freezing, steam, precipitation.


Radiation Fog: happens when ground radiates heat away, common at night and early in the morning. Can fly an RPAS short time after it dissipates. 


Ice/Freezing Fog: when radiation fog happens in the winter. Will turn into ice when it touches surfaces, like the drone rotors. 


Advection Fog: forms near the ocean, lasts for weeks


Upslope fog: fog that forms on a mountain, but can look like a cloud


Steam fog: cold, dry air moving over warm water picks up evaporating moisture 


Precipitation Fog: when rain falls into warm air (similar to steam fog)

Image Source: https://www.malteseislandsweather.com/mist-and-fog/

Precipitation

Precipitation is an important factor for pilots to contend with as they can affect the safe operation of an aircraft. 

Haze/Smoke: a visibility and legal concern. Stable air masses.


Blowing snow: brings visibility to near zero, and can lead to whiteout (cloud layer appears to merge with the surface)


Thunderstorms: present in all level of clouds, and pose significant threat to RPAS operation.generates strong updrafts and causes damage to the RPAS. Barometric pressure drop indicates approaching thunderstorm. 


Static electricity: discharges into lightning bolts. 


Tornados: product of intense updrafts. Extremely intense low pressure regions that suck up air into clouds.


Barometric pressure will normally fall with an approaching thunderstorm and rise when it has passed.

Image Source: https://globalnews.ca/news/3967652/what-do-you-do-when-youre-caught-in-a-whiteout/

Image Source: https://www.rmets.org/metmatters/types-lightning