ATSC113 Flying Weather Midterm 1

Convective clouds/cumuliform clouds

• look like stacks of cotton clouds

• Form when warm humid air rises through cooler surroundings air in the atmosphere

• Buoyancy associated with warm air drives strong updrafts (can be a hazard)

• Have flat bases, somewhat near to the ground

• Form wherever the air near the ground is colder than the ground or ocean surface

Stratiform clouds/ layer clouds

• Look like sheets/blankets

• Associated with layers in the atmosphere with different relative temperatures. When a horizontal wind moves warmer air towards cold wedges on ground, then warm air slides up along the top surface of the cold air because the warm air is more buoyant than the cold air.

• Often found along warm fronts

• Classified by altitude

• Hazards; if cold enough ice can form, visibility

Castellanus Clouds

Look like small castle turrets. Clue that the atmosphere is becoming unstable, thunderstorms possible later

Billow (K-H wave) Clouds

Unstable air aloft. Indicate wind shear which causes waves to form in a layer of air where cooler air underlies warm air. Indicates clear air turn turbulence (CAT)

Lenticular Clouds

• Form in the crests of mountain waves if air is relatively humid

• If there’s several humid layers of air at different altitudes, you can see a stack of lenticular clouds

• Indicate vertical wind oscillations and possible mountain wave-turbulence

• Sailplanes like because they can surf the wave and fly long horizontal distance, commercial aircraft’s hate because of bumpy ride

Rotor Clouds

• Indicate severe or extreme turbulence at low altitudes due to mountain waves

• Can break off aircraft wings

Banner Clouds

• Form on downwind side of mountain peak

• Indicate strong turbulence touching the downwind side of a tall isolated mountain peak

Pyrocumulus Clouds

• Form over forest fires and volcanoes,

• Indicate a forest fire so strong that the heat and moisture released can make a thunderstorm

Pileus Clouds

• Form over fast growing cumulus clouds

• Harmless

Fractus Clouds

• form in turbulent humid air near the ground

• Indicate high humidity or strong winds at low altitudes

Fumulus Clouds

• Water droplet clouds over cooling towers

• Harmless

Contrails Clouds

• Aircraft condensation trail

• Indicate turbulent wing-tip vortices behind

• Small aircraft’s can be flipped upside down

Relate cloud coverage amounts to the visual appearance of the sky

• The fraction of the sky covered by cloud is called sky cover/cloud cover

• - Measured in Olga’s

• Sometimes the sky is obscured, meaning there might be clouds but the observer on the ground can’t see them

• Tricky part of estimating cloud coverage is lower altitude clouds block higher altitude ones. To be safe, weather observers assume there are clouds behind low altitude clouds

• Advantage of flying vertically in aircraft is a good estimate at cloud coverage

Cloud Ceiling

• If a layer of clouds cover more than half the sky it’s called a ceiling

• The height above ground level of the lowest cloud base

• When visibility poor at ground level, ceiling is reported as vertical visibility

• Measured with; traditional ceilometers, laser ceilometers, ceiling balloons, pilot reports, weather observer estimates

Contrast horizontal visibility, vertical visibility, and runway visual range (RVR) and discuss how they affect aviation

• From plane straight down is vertical visibility, straight ahead is horizontal visibility , vertical angle is slant visibility

• Horizontal visibility is the ones measured/reported at airports because it’s most relevant for safety

• Runway visual range is measured by automated visibility sensors on a runway. Indicates how far ahead horizontally a pilot can see on the runway

• In obscuration conditions, the limit that you can see vertically is the vertical visibility and is used instead of ceiling height

VFR

• means that you fly by mostly looking out the window. You need good visibility and stay out of clouds

• If a pilot flies into the clouds they can loose control of the aircraft

IFR

You can conduct most of the flight by not looking out the window, instead navigate using online tools

IFC

Flying IFR in bad weather

IMC

Flying IFR in good weather

VFC/VMC

The name given to weather good enough to fly VFR

Fog

• Fog is a cloud that touched the ground, made of tiny liquid water droplets

• Can form due to 2 mechanisms;

• Water is added to unsaturated (non foggy air)

• Or unsaturated air is cooled to a dew point temperature

• More likely in humid air

Radiation Fog

During clear nights the ground cools by infra red radiation. Cold ground cools the air that touches the ground

Advection Fog

Humid air blows over a colder surface, causing air temp to decrease to dew point temperature

Upslope fog

When the wind blows air against a hill slope the air is pushed upward. When air rises gets sufficiently cold.

Precipitation or Front fog

Formed by adding moisture from the evaporation from warm rain drops falling down through unsaturated air

Steam fog

Occurs when cold air moves over warm humid surfaces(unfrozen lakes)

Obscuration: mist

Very small precipitation particles are gently falling through the air. Creates partial obscuration

Obscuration: smoke

Smoke can come from factories, cars, afforestation fires. Reduces visibility and could be toxic to breathe in if fly through

Obscuration: volcanic Ash

Consists of microscopic rocks with sharp edges. If they get in jet engines can break them by melting and resolidifying

Obscuration: sand

Strong winds over desserts can cause sand storms called haboobs. Similar effects on engine as volcanic ash, also can reduce visibility

Obscuration: haze

Consists of microscopic liquid water droplets, that form around a pollutant particle that attracts water vapour. Reduces visibility

Obscuration: spray

Breaking waves causing tiny droplets to be injected into the atmosphere. Reduces visibility.

Obscuration: Dust

Consists of a variety of microscopic solid substances. Visibility reduced

Identify the causes and typical locations of wind shear at aerodromes

• the change of wind speed or wind direction with altitude.

• Can happen at any altitude, almost always present near the ground

• Caused by weather systems and wind flowing across the mountains

• Associated with turbulence behind obstacles

• Caused by other large aircraft’s landing or taking off