Aviation Weather and Atmospheric Conditions

Vocabulary practice flashcards covering atmospheric concepts, turbulence, cloud types, weather advisories, fronts, fog types, and icing conditions based on aviation weather lecture notes.

Convective Turbulence

Turbulence caused by the convective activity of rising and sinking air.

Mechanical Turbulence

Turbulence caused by the physical obstruction of wind by trees, buildings, and mountains.

Lenticular Cloud

A standing lens-shaped cloud formed when stable air hits a mountain and rises, which can contain winds of $50\,\text{kts}$ or more.

Clear Ice

Hard-to-see ice that forms in temperatures from $5^\circ\text{C}$ to $-10^\circ\text{C}$ as water droplets freeze over an airfoil.

Mixed Ice

A combination of rime ice and clear ice that forms in temperatures ranging from $-10^\circ\text{C}$ to $-15^\circ\text{C}$.

Rime Ice

Ice that forms in temperatures from $-15^\circ\text{C}$ to $-20^\circ\text{C}$ and freezes instantly on impact, containing trapped air that makes it easier to clear.

AIRMET

An in-flight weather advisory issued every $6\,\text{hours}$ for moderate turbulence, moderate icing, mountain obscuration, or surface winds of $30\,\text{kts}$ or greater.

SIGMET

An in-flight weather advisory issued as needed (valid for $4\,\text{hours}$) concerning non-convective weather hazardous to all aircraft, such as severe turbulence, severe icing, volcanic ash, or widespread dust/sandstorms.

Convective SIGMET

A weather advisory issued for severe convective hazards to all aircraft, such as embedded thunderstorms, lines of thunderstorms, tornadoes, surface winds greater than $50\,\text{kts}$, or hail greater than or equal to $3/4\,\text{inch}$.

Troposphere

The layer of the lower atmosphere extending from the Earth's surface up to $36\text{,}000\,\text{ft}$, characterized by an average temperature decrease of $2^\circ\text{C}$ per $1\text{,}000\,\text{ft}$.

International Standard Atmosphere (ISA)

A standard baseline atmospheric model established at sea level with a standard pressure of $29.92\,\text{inHg}$ ($1\text{,}013.2\,\text{mb}$) and a standard temperature of $15^\circ\text{C}$ ($59^\circ\text{F}$).

Sublimation

The transition of a solid directly into a vapor state without passing through the liquid phase.

Dew Point

The temperature to which air must be cooled to become completely saturated.

Temperature Inversion

An atmospheric condition occurring on calm, cool nights where temperature increases with altitude, trapping weather, low clouds, fog, and pollutants underneath.

Advection Fog

Fog that forms when a layer of warm, moist air moves horizontally over a cold surface, common in coastal areas during winter.

Radiation Fog

Fog formed on calm, cool, clear nights over flatland areas due to rapid terrestrial radiation cooling (also known as valley fog).

Upslope Fog

Fog formed when stable, moist air is forced up terrain by wind and cools to its dew point as it ascends.

Steam Fog

Fog created when cold, dry air moves across warm water, frequently associated with low-level turbulence and icing.

Squall Line

A continuous lateral band of thunderstorms extending for hundreds of miles that continuously feeds itself.

Microburst

A localized area of intense downdrafts ($1\text{--}2\,\text{miles}$ in diameter) lasting up to $15\,\text{minutes}$ with downdraft speeds up to $6\text{,}000\,\text{ft/min}$.

Virga

Precipitation falling from a cloud that evaporates before reaching the Earth's surface, serving as a warning sign of wind shear or microbursts.

Induction Icing

Ice buildup that specifically affects an engine's air intake system, restricting required airflow.

Cold Front

A boundary where cold, dense air displaces warmer air at $25\text{--}30\,\text{mph}$, forcing warm air upward to produce cumulus clouds, rain showers, and scattered thunderstorms.

Warm Front

A boundary where warm air slides over a colder air mass, moving slowly at $10\text{--}25\,\text{mph}$ and bringing stratiform clouds, steady precipitation, and low visibility.

Convective Turbulence

Turbulence caused by the uneven heating of the Earth's surface, leading to vertical atmospheric movement via rising warm air and sinking cooler air.

Mechanical Turbulence

Turbulence created when wind is physically obstructed by surface features such as trees, man-made structures, and rough terrain or mountains.

Lenticular Cloud

A stationary, lens-shaped cloud formed over mountain peaks when moist, stable air flows over terrain; it signals severe mountain wave turbulence and winds of $50\,\text{kts}$ or more.

Clear Ice

A hard, heavy, and transparent ice that forms in temperatures from $5^\circ\text{C}$ to $-10^\circ\text{C}$ as large supercooled water droplets flow smoothly over an airfoil before freezing, making it difficult to detect.

Mixed Ice

A hazardous combination of rime ice and clear ice that forms in temperature ranges between $-10^\circ\text{C}$ and $-15^\circ\text{C}$, appearing as a rough and opaque accumulation on aircraft surfaces.

Rime Ice

A milky, opaque ice that forms in temperatures from $-15^\circ\text{C}$ to $-20^\circ\text{C}$ when tiny water droplets freeze rapidly upon impact, trapping air inside which makes it lighter and easier to clear.

AIRMET

An in-flight weather advisory issued every $6\,\text{hours}$ warning of moderate icing, moderate turbulence, sustained surface winds of $30\,\text{kts}$ or greater, or extensive mountain obscuration and IFR conditions.

SIGMET

An unscheduled in-flight weather advisory valid for up to $4\,\text{hours}$ concerning non-convective hazards safety-critical to all aircraft, including severe icing, severe turbulence, widespread dust storms, sandstorms, or volcanic ash.

Convective SIGMET

A severe weather advisory issued $55\,\text{minutes}$ past the hour (valid for up to $2\,\text{hours}$) for convective hazards to all aircraft, such as tornadoes, lines of thunderstorms, embedded thunderstorms, surface winds exceeding $50\,\text{kts}$, hail greater than or equal to $\frac{3}{4}\,\text{inch}$, or heavy precipitation covering at least $40\%$ of an area of at least $3\text{,}000\,\text{sq\,mi}$.

Troposphere

The lowermost layer of the Earth's atmosphere extending from the surface up to approximately $36\text{,}000\,\text{ft}$, containing nearly all weather activity and characterized by an average temperature lapse rate of $2^\circ\text{C}$ per $1\text{,}000\,\text{ft}$.

International Standard Atmosphere (ISA)

A standardized baseline atmospheric model at sea level consisting of a barometric pressure of $29.92\,\text{inHg}$ ($1\text{,}013.2\,\text{mb}$), a temperature of $15^\circ\text{C}$ ($59^\circ\text{F}$), and a lapse rate of $2^\circ\text{C}$ per $1\text{,}000\,\text{ft}$.

Sublimation

The phase transition in which a solid changes directly into a gaseous vapor without passing through the intermediate liquid state, such as dry ice converting to vapor when exposed to air.

Dew Point

The specific temperature to which a parcel of air must be cooled at constant pressure to become completely saturated with water vapor.

Temperature Inversion

An atmospheric condition occurring on clear, calm nights where air temperature increases with altitude, acting as a lid that traps weather, pollutants, fog, low clouds, and poor visibility near the surface.

Advection Fog

Fog created when a layer of warm, moist air moves horizontally over a cooler surface, common in coastal areas during winter; wind speeds of $15\,\text{kts}$ or greater usually cause it to lift into low stratus clouds.

Radiation Fog

Fog formed on clear, calm, cool nights over flat terrain when terrestrial radiation rapidly cools the ground and adjacent air to its dew point (also referred to as valley fog).

Upslope Fog

Fog created when stable, moist air is pushed gradually up rising terrain or mountains by wind, adiabatically cooling to its dew point as it ascends.

Steam Fog

Fog formed when cold, dry air drifts across a warm body of water, leading to evaporation that rapidly saturates the cold air above and creating low-level turbulence and icing hazards.

Squall Line

A severe, continuous lateral band of thunderstorms extending for hundreds of miles that self-propagates and often forms ahead of a cold front, posing intense hazards to flight.

Microburst

A localized, extremely severe downdraft ($1\text{--}2\,\text{miles}$ in diameter) lasting up to $15\,\text{minutes}$ with vertical downward velocities reaching $6\text{,}000\,\text{ft/min}$, producing severe wind shear and airspeed changes of $30\text{--}90\,\text{knots}$.

Virga

Streaks or wisps of precipitation that fall from a cloud but evaporate entirely before reaching the surface, serving as a visual indicator of severe low-level wind shear or microburst activity.

Induction Icing

The accumulation of ice within the air intake system or carburetor of an engine, restricting essential airflow and causing engine power loss or failure.

Cold Front

A fast-moving boundary ($25\text{--}30\,\text{mph}$) where a dense, cold air mass wedges beneath warmer air, forcing it upward rapidly to produce steep cumulus clouds, heavy rain showers, lightning, and potential squall lines.

Warm Front

A slow-moving boundary ($10\text{--}25\,\text{mph}$) where a warm air mass slides over colder air, producing widespread stratiform clouds, steady prolonged precipitation, low ceilings, and poor visibility.