Flashcards in Nature Of The Atmosphere Deck (168):
What is Air made up of?
1% Trace Gasses (Argon, Carbon Dioxide & traces of other gasses)
Name the 4 atmospheric layers and their boundary names?
Troposphere - tropopause.
Stratosphere - stratopause.
Mesosphere - mesopause.
How high is the Troposphere (tropopause)?
20,000ft (6km) over Northern and Southern Poles.
48,000 feet (14.5 km) over the equatorial regions.
How high is the Stratosphere (Stratopause)?
160,000 ft (50km)
How does temperature change with altitude inside the troposphere?
Temperature decreases at a rate of about 2°Celsius every 1,000 feet of altitude gain.
How does air pressure change with altitude inside the troposphere?
Pressure decreases at a rate of about 1 inch per 1,000 feet of altitude gain.
Why is the location of the tropopause important?
It is commonly associated with the location of the jetstream and possible clear air turbulence.
What is weather like inside the troposphere?
The vast majority of weather, clouds, storms, and temperature variances occur within this first layer of the atmosphere.
What is weather like inside the stratosphere?
Little weather exists in this layer and the air remains stable.
How high is the Mesosphere (mesopause)?
280,000 feet (85 km).
What happens to temperature inside the Mesosphere?
It decreases rapidly with an increase in altitude and can be as cold as -90°C.
At what altitude do the reactions of an average person start to become impaired due to oxygen levels?
10,000 ft and for some people as low as 5,000 ft.
What are some of the symptoms of Oxygen deprivation?
Mild disorientation to total incapacitation, depending on body tolerance and altitude.
How heavy is the atmosphere at sea level?
14.7 pounds/square inch
The actual air pressure at a given place and time will differ with WHAT?
Altitude, Temperature, and Air Density.
How is atmospheric pressure normally measured?
In inches of mercury (in. Hg.) by a mercurial barometer.
Name the 2 types of barometer?
What does ISA stand for?
International Standard Atmosphere
Standard sea level pressure is defined as WHAT?
29.92 in. Hg. at 59°F (15°C).
Atmospheric pressure is also reported in WHAT?
1 inch of mercury = approximately how many millibar's?
Standard sea level = how many millibars?
Typical millibar pressure readings range from WHAT to WHAT millibars.
950.0 to 1040.0
Tracking a pattern of rising pressure at a single weather station generally indicates the approach of WHAT?
Decreasing or rapidly falling pressure usually indicates approaching WHAT?
Bad weather and possibly, severe storms.
As altitude increases, pressure diminishes, as the weight of the air column decreases. This decrease in pressure is otherwise referred to as WHAT?
(An increase in density altitude)
At higher altitudes, with a decreased atmospheric pressure, relating to aircraft performance, WHAT 3 things are affected?
Takeoff and landing distances & climb rates.
Air currents and wind are caused by WHAT?
Temperature changes the air density which changes air pressure.
Clouds and precipitation (AKA weather) are caused by WHAT?
Motion in the atmosphere, combined with moisture.
Vertical (rising or falling) air movement is referred to as WHAT?
Horizontal air movement is referred to as WHAT?
The movement of air around the surface of the Earth is called WHAT?
What causes atmospheric circulation?
Atmospheric circulation is caused by uneven heating of the Earth´s surface creating changes in air movement and atmospheric pressure.
What is circulation theory?
Warm air rises in equatorial regions and sinks at polar regions.
What modifies circulation theory?
Several forces but mainly the earths rotation.
The force created by the rotation of the Earth is known as WHAT?
The Coriolis force deflects air in WHAT direction in the Northern Hemisphere.
To the right causing it to follow a curved path.
Does the Coriolis force have the same effect across the globe?
No it is greatest at the poles, and diminishes to zero at the equator.
The Coriolis force deflects air in WHAT direction in the Southern Hemisphere.
To the left causing it to follow a curved path.
The speed of the Earth´s rotation causes the general flow to break up into HOW MANY distinct cells in each hemisphere?
Friction forces due to the topography of the earth change both speed and direction of wind up to WHAT altitude?
Air flows from areas of WHAT pressure to WHAT pressure?
High to low.
In the Northern Hemisphere, the flow of air from areas of high to low pressure is deflected to the right; producing a clockwise circulation around an area of high pressure.
What is this clockwise circulation known as?
This is known as anti-cyclonic circulation.
In the Northern Hemisphere, the flow of air toward areas of low pressure is deflected to the left; producing an anti-clockwise circulation.
What is this anti-clockwise circulation known as?
Describe the air in a typical High-pressure system.
High-pressure systems are generally areas of dry, stable, descending air.
Good aviation weather is typically associated with (WHAT) pressure systems.
Name some ground surfaces that might give off large amounts of heat?
Plowed ground, rocks, sand, and barren land
Name some surface types that might absorb and retain heat?
Water, trees, and other areas of vegetation.
Define convective currents?
Uneven heating of the air creating small areas of local circulation.
During low altitude flights, up drafts are likely to occur over what surface types?
Pavement's or barren places
During low altitude flights down drafts are most likely to occur over what surfaces?
Water or expansive areas of vegetation like a group of trees.
Typically, turbulent conditions can be avoided by doing what?
Flying at higher altitudes, even above cumulus cloud layers.
During the day, which heats faster, land or water?
What is a sea breeze and when does it occur?
Air coming in from the sea during the day to replace rising land air.
What is a land breeze and when does it occur?
Air coming out to sea from the land during the night to replace rising sea air.
If you have to approach a runway on a sunny day over a car park then a lake, what might happen?
You may rise over the car park and fall over the lake.
Define wind shear?
A sudden, drastic change in windspeed and/or direction over a very small area
Directional wind changes of 180° and speed changes of 50 knots or more are associated with WHAT?
Low-level wind shear.
Low-level wind shear is commonly associated with WHAT?
Passing frontal systems, thunderstorms, and temperature inversions with strong upper level winds (greater than 25 knots).
In general, the most severe type of low-level wind shear is associated with WHAT?
Convective precipitation or rain from thunderstorms.
A microburst is a type of shear associated with WHAT type of weather?
How big is a typical microburst?
Less than 1 mile horizontally and within 1,000 feet vertically.
The lifespan of a typical microburst is HOW LONG?
About 15 minutes
How fast can the downdrafts be, in a microburst?
Up to 6,000 feet per minute
What does LLWAS stand for?
Low level wind shear alert system.
When windspeeds differ by more than HOW FAST, a warning for wind shear is given to pilots.
Is high pressure air more or less stable than low pressure air?
More stable than low presure air.
Does low pressure air bring with it good or bad aviation weather?
Why can a good understanding of high- and low-pressure wind patterns be of great help when planning a flight.
Because a pilot can take advantage of beneficial tailwinds
When planning a flight from west to east, favorable winds would be encountered along WHICH side of a high-pressure system or WHAT side of a low-pressure system.
North side of HIGH pressure and South side of LOW pressure.
On a flight from east to west the most favorable winds would be along WHICH side of a high-pressure system or WHICH side of a low-pressure system.
The southern side of a high-pressure system or the northern side of a low-pressure system.
What are isobars?
Lines drawn on a weather chart to depict areas of equal pressure.
On a weather chart, what do Isobars reveal?
The pressure gradient or change in pressure over distance.
What do closely spaced Isobars mean?
A steep pressure gradient and strong winds.
What do widely spaced Isobars mean?
A shallow pressure gradient and relatively light winds.
On a weather chart, what is a High?
A high is an area of high pressure surrounded by lower pressure.
On a weather chart, what is a low?
A low is an area of low pressure surrounded by higher pressure.
On a weather chart, what is a ridge?
A ridge is an elongated area of high pressure.
On a weather chart, what is a trough?
A trough is an elongated area of low pressure.
On a weather chart, what is a Col?
A col is the intersection between a ridge and a trough, or an area of neutrality between two highs or two lows.
Generally, the wind 2,000 feet above the ground will be WHERE in relation to surface winds?
20° to 40° to the right of surface winds and more parallel to isobars.
The stability of the atmosphere depends on its ability to resist WHAT?
What is Adiabatic Heating?
Air heating as it drops in altitude.
What is Adiabatic cooling?
Air cooling as it rises in altitude.
What happens to Pressure, Volume & Temperature when air rises?
Pressure decreases, Volume increases, and Temperature decreases.
What happens to Pressure, Volume & Temperature when air falls?
Pressure increases, Volume decreases, and Temperature increases.
What is Lapse rate?
The rate at which temperature decreases with an increase in altitude.
As air ascends through the atmosphere, the average rate of temperature change is WHAT °C (WHAT°F) per 1,000 feet?
What is lighter, water vapor or air?
What is the adiabatic lapse rate (°C/°F) of Dry (unsaturated) air per 1,000 feet?
3°C (5.4°F) per 1,000 feet.
What does the moist adiabatic lapse rate vary from ?°C to ?°C (?°F to ?°F) per 1,000 feet?
1.1°C to 2.8°C (2°F to 5°F) per 1,000 feet.
Cool, Dry air is likely to be which of the following?
Stable or UnStable
Moist, Warm air is likely to be which of the following?
Stable or UnStable
What is an Inversion Layer?
A shallow layer of smooth, stable air close to the ground with air temperature rising with altitude.
When are you most likely to find a surface based temperature inversion?
On clear, cool nights
Describe a Frontal inversion?
When warm air spreads over a layer of cooler air, or cooler air is forced under a layer of warmer air.
How much does air need to heat up to hold double the amount of moisture?
Water is present in the atmosphere in three states, what are they?
Liquid, solid, and gaseous.
As water changes from one state to another, an exchange of heat takes place. These changes occur through WHICH processes?
Evaporation, sublimation, condensation, deposition, melting, or freezing.
Water vapor is only added into the atmosphere by the processes of WHAT and WHAT?
Evaporation and Sublimation.
Evaporation is the changing of liquid water to water vapor.
Define the latent heat of evaporation?
Water vapor forming and absorbing heat from the nearest available source.
The changing of ice directly into water vapor.
What is Relative Humidity?
The actual amount of moisture in the air compared to the total amount of moisture the air could hold at that temperature
At sea level pressure, how many grams of water can a square meter of air hold at the following temperatures?
9g at 10°C
17g at 20°C
30g at 30°C
The temperature at which air can hold no more moisture.
When lifted, unsaturated air cools at a rate of (WHAT) per 1,000 feet
When lifted, the dewpoint temperature decreases at a rate of (WHAT)°F per 1,000 feet
When lifted, unsaturated air cools at a set rate and the dewpoint temperature decreases at a different rate. This results in a convergence of temperature and dewpoint at a rate of (WHAT)°F?
Convergence rate of 4.4°F.
If you know the Temperature and Dewpoint, how can you work out the approximate height of the cloud base?
Temperature — DewPoint = Temperature Dewpoint Spread (TDS)
TDS÷Convergence Rate(4.4°F) = A
Ax1,000 feet = height of cloud base AGL
There are four methods by which air can reach the complete saturation point. What are they?
1. Warm air moving over a cold surface.
2. Cold and warm air mixing.
3. Air cooling at night through contact with the cooler ground.
4. Air being lifted or forced upward.
Why is Frost dangerous to flight?
It disrupts airflow over the wing reducing lift and it increases drag.
A cloud beginning within 50 feet of the surface.
Name the 5 types of Fog?
1. Radiation Fog
2. Advection Fog
3. Upslope Fog
4. Steam fog, (AKA Sea Smoke)
5. Ice fog
If radiation fog is less than 20 feet thick, it is known as WHAT?
What causes Radiation Fog?
Ground cools rapidly and air reaches its dew point.
What causes Advection Fog?
Warm, moist air moving over a cold surface.
What causes Upslope fog?
Moist, stable air forced up sloping land features.
What causes Steam Fog?
Cold, dry air moving over warm water.
What causes Ice Fog?
In freezing weather water vapor forms ice crystals.
What is the opposite of deposition?
What is the opposite of sublimation?
What is condensation nuclei?
dust, salt, and smoke particles.
What is cloud type determined by?
Height, Shape, and Behavior.
Low clouds are those that form near the Earth´s surface and extend up to HOW HIGH?.
6,500 feet AGL
Typical low clouds are WHAT,WHAT, and WHAT?
Stratus, Stratocumulus, Nimbostratus and Fog.
Middle clouds form around (HOW HIGH) and extend up to (HOW HIGH)?
6,500 ft AGL up to 20,000 ft AGL
Typical middle-level clouds include WHAT and WHAT?
Altostratus and Altocumulus.
High clouds form above HOW HIGH?
20,000 ft AGL.
Typical high-level clouds are, WHAT, WHAT AND WHAT?
Cirrus, Cirrostratus, and Cirrocumulus.
Clouds with extensive vertical development are called WHAT?
Towering Cumulus or cumulonimbus clouds.
When a large Cumulonimbus is obscured by other cloud formations what term describes this type of weather?
An Embedded Thunderstorm.
What do you call a Heaped or piled cloud?
What do you call clouds formed in layers?
What do you call clouds with ringlets; fibrous clouds; also high-level clouds above 20,000 feet.
What do you call clouds with a common base with separate vertical development; castle-like.
What do you call clouds with a lens shape; formed over mountains in strong winds.
What do you call rain bearing clouds?
What do you call clouds that are ragged or broken?
What are the names of the 2 types of Cumulonimbus (AKA - thunderstorms)?
Air mass thunderstorm
What causes an Air mass thunderstorm?
Heating of the air near the Earth´s surface.
What causes an Orographic thunderstorm?
The upslope motion of air in mountainous regions.
Cumulonimbus clouds that form in a continuous line are called WHAT?
Non-frontal bands of thunderstorms or squall lines
A thunderstorm makes its way through three distinct stages before dissipating. WHAT ARE THEY?
How high can a Thunderstorm get to?
50,000 feet to 60,000 feet depending on latitude.
If flying around a thunderstorm, how many miles clearance should you give it?
If you can't fly around a thunderstorm, what should you do?
Stay on the ground until it passes.
Drizzle is classified as very small water droplets, smaller than WHAT SIZE?
Smaller than 0.02 inches in diameter
Rain that falls through the atmosphere but evaporates prior to striking the ground is known as WHAT?
Ice pellets are an indication of WHAT?
A temperature inversion.
What is an Air Mass?
Large bodies of air that take on the characteristics of the surrounding area, or source region.
Air masses are classified based on their region of origination. What are they categorized as?
(Polar or Tropical)
(Maritime or Continental)
What is a Front?
The boundary layer between two types of air masses.
There are four types of fronts, which are named according to the temperature of the advancing air as it relates to the temperature of the air it is replacing.
What are they?
What is a Warm Front?
A warm mass of air overlapping a body of colder air.
How fast are warm fronts?
Warm fronts move slowly, typically 10 to 25 miles per hour (m.p.h.).
What is a Cold Front?
A mass of cold, dense, and stable air advancing and replacing a body of warmer air.
How fast are cold fronts?
25 to 30 m.p.h. Usually however, extreme cold fronts have been recorded moving at speeds of up to 60 m.p.h
What is an Occluded Front?
A fast-moving cold front catching up with a slow-moving warm front.
What is a cold front occlusion?
A fast-moving cold front that is colder than the air ahead of the slow-moving warm front.
What is a Warm front occlusion?
The air ahead of the warm front is colder than the air of the cold front.
Describe flying toward a warm front.
Clouds/visibility/precipitation and ceilings all worsen the closer you get.
Prior to the passage of a warm front, which direction would you expect the wind to be coming from?
During the passage of a warm front what direction would you expect the wind to be blowing from?
After the passage of a warm front which direction would you expect the wind to blow from?
Flying toward a warm front, how do the clouds change (from what to what.....)?
Cirrus to Cirrostratus to Altostratus to Nimbostratus.
A high dew point and falling barometric pressure are indicative of WHAT?
Imminent cold front passage.