Atmospheric Structure

Atmoshperic Composition

78% nitrogen, 21% oxygen, and 1% other gases

Troposphere

-The lowest layer of Earth's atmosphere

-Varies in height (36,000 ft over US)

-Large amounts of moisture and condensation nuclei are found here

-Most weather occurs here

-Std lapse rate

-Winds increase with altitude

Tropopause

-Transition zone between the troposphere and stratosphere

-Abrupt change in rate of temperature decrease

-36,000 ft MSL above US

-Temperature is constant with altitude (isothermal) (coldest area in lowest atmosphere (we get contrails)

Where do the strongest winds occur?

Just below the tropopause, resulting in moderate to severe turbulence

-Also find a haze layer here

Stratosphere

-Above tropopause

-Increasing temperature (inversion) as altitude increases

-Thin air, smooth flying and great visibility

Temperature Lapse Rate

Decrease in temperature with increase in altitude

What are the three environmental/existing lapse rates?

Standard, Isothermal, and Inverted

Standard Temperature Lapse Rate

2 Deg C (3.5 deg F) per 1000 ft

Standard pressure lapse rate

1 inHg (34 mb) per 1000 ft

Isothermal Lapse Rate

Temperature is constant with increasing altitude

Temperature Inversion

Temperature increases with increasing altitude

The average weight of air on a square inch of earth's surface is?

14.7 lbs

Does pressure decrease as altitude increases?

Yes

Does air density decrease as altitude increases?

Yes

standard sea level pressure

29.92 in Hg

standard sea level temperature

15 deg C or 59 deg F

Station pressure

atmospheric pressure measured at the observing station

Sea Level Pressure

The atmospheric pressure at mean sea level

Surface Analysis Chart

depict high and low pressure systems as they move across the country

Blue H

high pressure symbol

Ridges

High pressure areas/good weather

Troughs

Low pressure area/poor weather

Altimeter Error Temperature

4% error for every 11 degrees C from standard

If the air is colder than a standard atmosphere, the aircraft will be ______ than the altimeter indicates

Lower

If the air is warmer than the standard atmosphere, the aircraft will be ______ than the altimeter indicates.

Higher

When flying from low to high pressure, if the altimeter is not updated, the aircraft will be ____ than the altimeter indicates

Higher

When flying from high to low pressure, if the altimeter is not updated, the aircraft will be ____ than the altimeter indicates

Lower

Indicated Altitude

Altitude read directly from the altimeter.

Absolute Altitude

height above the surface (AGL)

True Altitude

height above mean sea level (MSL)

Pressure Altitude

height above the standard datum plane

Density altitude

Pressure altitude corrected for nonstandard temperature

What resource contains altitude corrections for extreme cold temperatures (<0 deg C)?

Flight Information Handbook

What three forces affect the flow of wind?

Pressure Gradient Force, Coriolis Force, Friction

For wind speeds, pennants indicate how many knots?

50

For wind speeds, single barb indicates how many knots?

10

For wind speeds, half bard indicate how many knots?

5

Isobars

Lines joining places on the map that have the same air pressure; usually 4 millibars apart

What is the initiating force for all winds?

pressure gradient force

Tighter spacing of the isobars shows a ____ ___ gradient thus a strong PGF and ____ winds.

steep pressure, stronger

Wider spacing indicates a ____ ____ gradient producing a weaker PGF and ____ winds.

shallow pressure, weaker

Gradient winds generally move ____ to isobars.

Parallel

Pressure gradient force is perpendicular to isobars ____ low pressure and ____ of high pressure.

Into, Out

Gradient winds flow _____ around high pressure areas and ____ around low pressure areas.

clockwise, counterclockwise

Coriolis Force

The apparent force, resulting from the rotation of the Earth, that deflects air to the right.

Gradient winds are generally found above _____ feet AGL

2000

The combined result of the ____ ____ ____ and ____ ____ is gradient wind which flow ____ to pressure gradient force and ____ to isobars.

Pressure Gradient Force, Coriolis Force, Perpendicular, Parallel

Gradient winds flow ____ around highs and ____ around lows.

Clockwise, counterclockwise

Surfaces are found below ____ ft AGL

2000

Surface winds cross isobars at ____ degs

45

Local winds are created by ____, ____, and ____.

mountains, valleys, and bodies of water

West bound aircraft will encounter strong ____ which will ____ fuel consumption.

headwinds, increase

Rising air has ___ pressure and ____ temperature

low, high

Descending air has ___ pressure and ____ temperature

high, low

Sea Breeze

During the day, cool more dense air from the sea moves towards land causing the warm less dense air to rise over the land.

Land Breeze

At night, cool more dense air from the land moves towards the sea causing the warm less dense air to rise over the sea.

Valley Wind

During the day, air warms and rises from the valley and up the slopes.

Mountain wind

At night, cool air flows downhill to cool the mountain slopes.

Saturation

Air contains the maximum amount of water vapor it can hold for a particular temperature.

Dewpoint

the temperature at which saturation occurs and is a direct indication of the amount of moisture in the air

The higher the dewpoint, the ____ the chance of clouds, fog, or precipitation.

Greater

Dewpoint Spread

The difference between the air temperature and dew point temperature

Relative Humidity

The percentage of water vapor in the air compared to the maximum amount of water vapor that air can contain at a particular temperature

What are three characteristics of precipitation?

Showers, Continuous, Intermittent

Showers

Starts, stops, changes intensity or sky conditions rapidly

Showers are associated with what type of cloud?

Cumuliform

Continuous

steady and changed intensity gradually

Continuous is associated with what type of cloud?

Stratiform

Intermittent

stops and starts at least once during the hour

Intermittent is associated with what types of clouds?

Cumuliform or stratiform

What are three types of precipitation?

Drizzle - liquid and freezing;

Rain - liquid and freezing;

Frozen - hail, ice pellets, snow, and snow grains

Cloud Formation

Formed when the air becomes saturated either by cooling to the dew point or through the addition of moisture

Low Clouds Range

Surface to 6,500 ft AGL

Types of Low Clouds

Cumulus, towering cumulus, stratocumulus, stratus, and cumulonimbus

Low Clouds Turbulence Level

None to moderate

Low Clouds Precipitation

Light rain or drizzle; can produce icing at or below

Middle Clouds Range

6500 to 20000 ft AGL

Types of Middle Clouds

altocumulus, altostratus, nimbostratus

Middle Clouds Composition

water droplets, supercooled liquid water droplets and/or ice crystals

Middle Clouds Precipitation

Rain, snow, and icing

High Clouds Range

20000 to 40000 ft AGL

Types of High Clouds

cirrus, cirrocumulus, cirrostratus

High Clouds Composition

Ice crystals

High Clouds Precipitation

None

Which clouds are nearing the thunderstorm stage and can produce continuous rain, snow, or ice pellets?

Towering Cumulus and Cumulonimbus

Which cloud can produce continuous rain, snow, or ice pellets?

Nimbostratus

Which cloud is the exceedingly dangerous thunderstorm cloud?

Cumulonimbus

Special Clouds

lenticular, contrails, asperitas, nacreous, supercells, virga

Stable

Lifted air that is colder than surrounded air settles when lifting action is removed because it is denser.

Unstable

Lifted air that is warmer than surrounded air settles when lifting action is removed because it is less dense.

Neutrally stable air

Lifted air that has same temperature as surrounding air after it is lifted so it remains at the same point where the lifting was removed.

Four methods by which air masses are lifted

Convergence, frontal, orographic, and thermal

convergence lifting

Air masses converge and force air upward

frontal lifting

Cold front lifts warm air up

orographic lifting

an air mass is forced to rise over a topographic barrier

Thermal lifting

caused when cool air is over a warm surface and is heightened by intense solar heating

____ clouds usually develop with stable conditions, while ____ clouds appear in unstable conditions

Stratiform, cumuliform

Stable air is indicated by (cloud type, turbulence, visibility, winds, precipitation, icing, temperature)

stratus clouds, smooth turbulence, poor visibility (low clouds or fog), steady winds, steady precipitation, rime icing, and temperature inversion

Unstable air is indicated by (cloud type, turbulence, visibility, winds, precipitation, icing, temperature)

cumulus clouds (thunderstorms), rough turbulence, good visibility, gusty winds, showery precipitation, clear icing, rapidly decreasing temperatures when climbing