1. Height above Earth's surface where the lowest cloud layer base or obscuring phenomena aloft exists that can be classified as broken (BKN) or overcast (OVC) 2. Vertical visibility into a surface-bases total obscuration

Weather Theory Flashcards by Bryn Chase

What is ideal air?

Air that lacks moisture
Nitrogen (N2) ≈ 78%
Oxygen (O2) ≈ 21%
Other ≈ 1%

How well did you know this?

Not at all

Perfectly

What is coastal air?

Nitrogen (N2) ≈ 74%
Oxygen (O2) ≈ 20%
Other ≈ 1%
Water Vapor ≈ 5%

How well did you know this?

Not at all

Perfectly

What are the phases of a microburst?

Formation, impact and dissipation

How well did you know this?

Not at all

Perfectly

What are the 5 types of air masses?

Continental Arctic (cA
Continental Polar (cP)
Continental Tropical (cT)
Maritime Polar (mP)
Maritime Tropical (mT)

How well did you know this?

Not at all

Perfectly

Low density altitude reflects _____ than standard (ISA) temperature

Lower/colder

How well did you know this?

Not at all

Perfectly

Higher density altitude reflects _____ than standard (ISA) temperature

Higher

How well did you know this?

Not at all

Perfectly

A ground-based inversion develops on _____ nights with _____ wind.

Clear cool nights, calm wind

How well did you know this?

Not at all

Perfectly

As moisture increases, air density _____.

Decreases

How well did you know this?

Not at all

Perfectly

As temperature increases, air density _____.

Decreases

How well did you know this?

Not at all

Perfectly

As air pressure decreases, air density _____.

Decreases

How well did you know this?

Not at all

Perfectly

How is servere icing defined?

Rate of ice accumulation is such that the ice protection systems fail to remove
2.Ice is accumulating in locations not normally prone to icing

How well did you know this?

Not at all

Perfectly

What are the five types of temperature variation?

1.Latitude - variations as you move further from the equator
2. Seasonal - variations due to the Earth’s tilt toward or away from the sun
3. Diurnal - variations in temp from day to night
4. Topography - land near water masses have smaller variation, arid regions permit greatest variations
5. Altitude - temperature lapse rate

How well did you know this?

Not at all

Perfectly

Clear air turbulence (CAT) that is associated with a jet stream is most commonly found in the vicinity of the _____ and _____ fronts.

Tropopause, upper fronts

How well did you know this?

Not at all

Perfectly

What is the size of a jet stream?

Thousands of miles long, hundreds of miles wide, thousands of feet tall

How well did you know this?

Not at all

Perfectly

A jet stream flows in or near the _____ in a corkscrew path with the upward motion on the _____ side and the downward motion on the _____ side.

Tropopause, equatorial, polar

How well did you know this?

Not at all

Perfectly

Define a jet stream

Narrow bands of wind with a speed of 50 KTS or greater

How well did you know this?

Not at all

Perfectly

How does advection fog form?

When moist air moves over cooler ground or water. Will dissipate/lift when winds exceed 15 KTS.

How well did you know this?

Not at all

Perfectly

How does fog form?

When the temperature, dew point, or both increase causing the air to become saturated.

How well did you know this?

Not at all

Perfectly

Define VFR

Ceiling > 3,000’ or none AND visibility > 5 SM

How well did you know this?

Not at all

Perfectly

Define MVFR

M - Marginal
Ceiling = 1,000’ - 3,000’ and/or visibility = 3-5 SM

How well did you know this?

Not at all

Perfectly

Define IFR

Ceiling < 1,000’ and/or visibility < 3 SM

How well did you know this?

Not at all

Perfectly

Define LIFR

L - Low
Ceiling < 500’ and/or visibility < 1 SM

How well did you know this?

Not at all

Perfectly

Define ceiling

Height above Earth’s surface where the lowest cloud layer base or obscuring phenomena aloft exists that can be classified as broken (BKN) or overcast (OVC)
Vertical visibility into a surface-bases total obscuration

How well did you know this?

Not at all

Perfectly

How is a severe thunderstorm defined?

Surface winds ≥ 50 KTS and/or surface hail diameter ≥ 3/4”

How well did you know this?

Not at all

Perfectly

It is recommended to pilots that they clear the top of a known or suspected severe thunderstorm by how much?

1,000' for each 10 KTS of wind speed

_____ are hidden convective clouds

Embedded cumulonimbus clouds

What are the characteristics of a steady state thunderstorm?

1. Formed from weather systems 2. More destructive 3. Longer in duration

What are the characteristics of an air mass thunderstorm?

1. Formed from convection 2. Self-destructive 3. Shorter in duration

What are the two classes of thunderstorms?

1. Air mass (AMS) 2. Steady state (SSTATE)

Describe the dissipating stage of a thunderstorm.

Predominantly downdrafts, microburst activity more likely

Describe the mature stage of a thunderstorm.

Both updrafts and downdrafts, precipitation begins to fall, lightning

Describe the formation stage of a thunderstorm.

Primarily updrafts, towering cumulus clouds forming

What are the three life stages of a thunderstorm?

Developing, mature, dissipating

What three conditions are necessary for a thunderstorm to form?

water vapor, unstable air, lift

Frost produces a roughness on the aerodynamic surfaces which may decrease lift by _____ and increase drag by _____.

Lift by 30%, drag by 40%

Frost forms near the Earth's surface primarily on clear night with _____ air and _____ winds.

Stable air and light winds

What mid-level clouds are associated with mountain wave activity?

Alto-cumulus standing lenticular

What high-level clouds are associated with mountain wave activity

Cirro-cumulus standing lenticular

What three conditions are necessary for mountain wave activity?

1. Stable air 2. Winds ≥ 30-40 KTS 3. Wind blowing perpendicular to the mountain

Define frontogenesis

Development of a front

Define frontolysis

Dissipation of a front

What can you expect if there is a change in temperature ≥ 5℃ across a front?

Moderate or greater turbulence

Define Front

A boundary between two air masses

What are the characteristics of stable air?

Statiform clouds/fog, continuous precipitation, smooth air, fair to poor visibility

What are the characteristics of unstable air?

Cumuliform clouds, rain showers, turbulence likely, good visibility

Define air mass

A body of air with uniform temperature and moisture

What are the four cloud families?

1. High 2. Middle 3. Low 4. Clouds with extensive vertical development

What is the measurement of atmospheric instability?

Lifted Index

What determines stability?

Ambient temperature lapse rate

Precipitation may be anticipated when clouds are reported to be at least _____.

4,000 FT

What is supercooled water?

Liquid drops below freezing ex: freezing rain & freezing drizzle

What are microscopic particles that can become condensation surfaces called?

Condensation nuclei

What are the four states of water?

1. Condensation 2. Evaporation 3. Sublimation 4.Deposition

When can you anticipate fog?

When the temperature/dew point spread is ≤ 3℃ and decreasing with light winds

Define dew point

Temperature to which air must be cooled to become saturated

Define relative humidity

The actual water vapor present compared to that which could be present

Define windshear

A rapid change of windspeed and/or direction over a relatively short time, distance or direction

How do high pressure winds flow?

Clockwise (anti-cyclonic), outward, downward

How do low pressure system winds flow?

Counter-clockwise (cyclonic), inward, upward

What is Coriolis Force?

Deflection of winds due to the Earth's rotation (to the right in northern hemisphere)

What drives winds across isobars and contours from higher to lower pressure?

Pressure gradient force

Define advection

The horizontal movement of air

Define convection

Rising air

High Density Altitude (DA) does what to takeoff roll and runway requirement?

Increases

High Density Altitude (DA) does what to performance and climb rate?

Decreases

At lower than standard temperatures, density altitude is _____ than pressure altitude

Less than

Define density altitude.

Pressure altitude corrected for non-standard temperature

Lower pressure results in _____ pressure altitude

Higher

Define pressure altitude

Indicated altitude when using 29.92

Define indicated altitude

Altitude above MSL indicated on altimeter when using local altimeter setting.

Pressure drops faster in _____ air

Colder

What is the normal pressure lapse rate?

1℃/1,000' up to ≈ 10,000' MSL

What is an altimeter setting?

The sea level pressure value to which the scale of the altimeter is set.

What is QNH?

Local altimeter setting

_____ is the actual pressure at field elevation, written as QFE.

Station pressure

Inversions can commonly be found at _____.

The base of the stratosphere

What is an inversion?

An inverted temperature lapse rate.

What hazards are associated with an inversion?

Poor visibility, icing, turbulence

Air density _____ with increased altitude.

Decreases

What is the primary characteristic of the stratosphere?

It's primarily isothermal

The average depth of the tropopause is usually no more than _____.

A few thousand feet

What is the primary characteristic of the tropopause?

An abrupt change in the temperature lapse rate

The tropopause is a _____ layer that separates the troposphere and stratosphere.

Non-continuous

Wind speed normally decreases with altitude within the _____.

Stratosphere

Wind speed normally increases with altitude within the _____.

Troposphere

The average thickness of the troposphere in the mid-latitudes is _____.

≈ 36,000'

The troposphere layer is thickest at the _____.

Equator

All weather originates in the _____.

Troposphere

What is the primary characteristic of the troposphere?

Its temperature lapse rate

What is ISA (International Standard Atmosphere)?

Average weather parameters 15℃ or 59℉ 1013.2 mb(hPa) or 29.92"

Air _____ as altitude increases.

Expands

Air expansion results in lower air ____, ____ and density

Pressure and temperature

Describe vertical windshear

VWS = ∆Speed／∆Altitude VWS ≥ 6KTS/1,000' = Moderate turbulence VWS ≥ 10KTS/1,000' = Severe Turbulence Usually seen on climb/descent

Describe horizontal windshear

HWS = ∆Speed / Distance HWS ≥ 18 KTS / 150 NM = Moderate turbulence HWS ≥ 40 KTS / 150 NM = Severe turbulence Usually seen while cruising

When you change the composition of the air, you change the _____ of the air.

Density

As altitude increases, _____, _____, and _____ decrease.

Pressure, temperature, and density

True or False: Cumulonimbus tops may overshoot into the stratosphere

True

True or False: Wind speed increases with altitude in the troposphere

True

Air expands as altitude increases due to _____

Decreasing pressure

As air density decreases, aircraft performance ______.

Decreases

As pressure decreases, air density _____

Decreases

Inversions are associated with _____ air

Stable

Hazards associated with inversions

Poor visibility, Icing, turbulence

What is a barometer?

Instrument used to measure atmospheric pressure

As we move upward through the atmosphere, the weight of the air above us ______

Decreases

Pressure decreases faster in ______ air

Colder air

Surface lows typically move from the ______ to the _____

From the west to the east

Low pressure systems with faster horizontal movement are referred to as _____

- Leaning lows - Implies faster winds aloft

High pressure systems are associated with _____ weather

Better

What determines how much water vapor a parcel ofair can hold?

Temperature

During winter, polar jet streams migrate _____, increase in altitude, and become _____

migrate south, become more intense

Subtropical jet streams are most active during _____

Winter

Most turbulence occurs on the _____ side of a jet stream, in the curves of an _____ trough

polar side, upper trough