EXAM ( Weather ) Flashcards
clouds
What are the 3 cooling process
Adiabatic
Cooling due to change in pressure - expansion of air
Nocturnal (stratus)
“night sky cooling”
Heat radiates away from an object/surface to the nightsky
Advection
Caused by warm air passing over cold surface
What are the 4 low clouds ?
Cumulus (CU)
Unstable - no rain
Stratus (ST)
Stable - no rain
Stratocumulus (SC)
Inbetween (stabile/unstabile)
Cumulusnimbus (CB)
Unstable - Rain
Is vertical clouds stable or unstable ?
unstable
What does stability in clouds mean ?
Look up
How likely they are to lift vertical and have percipitation.
(Unstable = Lift vertical and can hold rain)
What are the middle clouds ?Name + Abbreviation + characteristics
Altostratus (AS)
Stable no rain
Altocumulus (AC)
unstable no rain
Nimbusstratus (NS)
Stable + rain
What are the high clouds ?Name + Abbreviation + characteristics
Cirrus (CI)
No stability linked - no rain
Cirrostratus (CS)
Stable (stratus) - no rain
Cirrobumulus (CC)
Unstable (cumulus) - no rain
What’s natural air ?
Dry air + Condensation nuclei + Water vapor
What’s the composition of the atmosphere ?
78% Nitrogen
21% Oxygen
1% Argon and other
What’s the 5 atmospheric layers?
Troposphere
Stratosphere
Mesosphere
Thermosphere
Exosphere
What is atmospheric circulation (Three cell theory) caused by ?
1 Uneven heating
2 Tilt of the earth
3 Coriolis force
atmospheric circulation
Where is the wind coming from (what are they called) ? :
1 0-30º lattitude
2 30-60º lattitude
3 60-90º lattitude
1 NE trade winds
2 Westerlies
3 Polar easterlies
4 Changes that have to be seen for a front to be in place
- Temperature change
- Dew point number change -
Increase warmfront - drop coldfront
(moister content of airmass is DP) - Pressure fall then rise
(Decreasing as low pressure comes in - as front moves away then high pressure behind increases pressure) - Wind shift
3) all fronts are low pressure
What are the 6 air mass “codes” ?
C = Continental (dry air)
M = Maritime (moist air)
A = Arctic (70-90º - cold)
P = Polar (40-60º - cold)
T = Tropical (10-30º - warm)
E = Equatorial (0-10º - warm)
What are the 4 types of heat transfer ?
briefly describe
Radiation (electromagnetic waves)
Conduction (Touch)
Convection (movement of partical transporting heat from warm to cold - Vertical)
Advection (horizontal moving air)
What is the “OLR”
Observed lapse rate
A change in temperature with altitude
2º per 1000’
Is seabreez an exampel of convection og advection - why ?
Advection because air is being “sucked” horizontally from the sea into land where air is being warmed and lifted - therefore creating a void to be filled.
What’s a temperature inversion ?
An altitude where this is warmer air above colder air temperature is increasing with altitude
What are the two types of temperature inversions ?
1 Radiation - nocturnal
(ground releases heat at night and air above is warmer than at the surface)
2 Frontal
(When a cold airmass undercuts a warm airmass - cold airmass can push beneath because it’s more dense)
What can prevent a radiation temperature inversion ?
Cloud layer (OVC) above the ground deflects the heat back down again
Simply put - What’s the difference between convection & advection ?
Convection is vertical
Advection is horizontal
What causes wind speeds ?
PGF Pressure gradient force
Would you expect the wind to be strongest at point A or B ?
B - Due to the isobars laying closer together
If you have a left crosswind pushing you to the left - are you moving towards or away from low pressure ?
Moving towards low pressure
If you go from KOZR with an altimeter setting of 30.22 to KMAI 30.01 - and you don’t correct you kollsman window - what is your true altitude in regard to you indicated ?
“From high to low - look out below” = your true altitude is lower than your indicated
How does moister in the air affect flight performance?
Moister = less air density = higher density altitude = reduction in lift and engine performance
Name the 3 atmospheric conditions which provide the best lift
1) High pressure
2) Low humidity
3) Low temperature
What type of clouds would you expect at low altitude in an unstable enviroment ?
Cumuliform clouds
What type of clouds would you expect at low altitude in an stable enviroment ?
Statiform clouds
All fronts are _____
Low pressure
____ are lines of equal pressure, seperated by ____ mb. Above ____ the wind blows ____ to the ____
Isobars are lines of equal pressure, seperated by 4 mb. Above 2000’ the wind blows parallel to the isobars
What’s the standard atmospheric pressure - Hg & hP/mb
29.92 Hg
1013.2 hP/mb
What’s the characteristics of a High pressure system/weather?
Sinking air near center
Clockwise wind direction
Divergence (air moves away)
Good visibility
Good flying conditions
What’s the characteristics of a Low pressure system/weather?
Lifting air near center
Counterclockwise wind direction
Convergence (air moving towards)
Limited visibility due to clouds/fog/rain
Poor flying conditions
What information can be deduced from the isobars ?
- High / low pressure
- Wind direction
- Relative wind speeds
What’s the definition of the pressure gradient force ?
Rate at which air will accelerate depends on rate at which pressure changes with distance
Which force causes the wind to blow ?
Uneven heating og earths surface creating a Pressure gradient force
How does coriolis force affect circuling air in the northern hemisphere ?
Deflection to the right (from the direction of movement)
Which two forces affect global wind direction ?
Pressure gradient force and coriolis
(uneven heating is the reason the winds occur)
How does the wind flow in relation to the isobars below 2000’
Across the isobars
Buys ballot’s law
Standing with your back to the wind - the low pressure will be to your? (left/right)
Left
When you’re moving towards a low pressure - what weather conditions should you expect ?
Lifting air, vertical clouds, turbulence and possible storms
Explain which states (from/to) each refer to:
Sublimation
Deposition
Evaporation
Condensation
Sublimation
Solid to gas
Deposition
Gas to solidt
Evaporation
Liquid to gas
Condensation
Gas to liquid
When somthing is “saturated” what does that mean ?
It’s holding as much water/moister as possible
What’s “dew point” ?
A temperature at which the air is saturated - beyond this visible moister and rain will form.
2 degrees before dew point = visible moister possible
What’s relative humidity ?
A procentage of how humidt the air is in regard to how much water is can hold.
What’s an adiabatic process ?
A change in temperature without heat transfer.
Energy transfered due to work (compression of gas or expansion)
Air pushed up the mountain - expands and cools ?
What happens at LCL ?
what’s saturation in % ?
Clouds start to form
100% saturation / relative humidity
What’s a front ?
A boundary between air masses of different density
Frontal weather is caused by the lifting of ____ and ____ air by ____ and more ____ air
Frontal weather is caused by the lifting of warm and moist air by colder and more dense air
Does all fronts have temperature inversions ?
YES
What 4 things would you expect a change in during a frontal passage ?
1 Temperature
2 Dew point
3 Pressure “fall then rise”
4 Wind shift (approx. 90º)
What happens when warm air is lifted over cold air ?
The warm air cools with altitude, condenses and creates clouds
“Make weather”
Cold front
Clouds assosiated ?
Cumuliform
What’s a squall line ?
and which front is it assosiated with ?
A line of thunderstorms
cold fronts
When the altimeter setting is decreasing and then starts to increase - which front has passed ?
a cold front
Cold front
Which direction does the wind blow from behind and infront of the front ?
Behind: NW
Infront: SE
What happens to temperature when the cold front has passed ?
It’s lower - colder air
How does a faster cold front affect weather
It becomes more severe - squall lines could form
What’s the sequence of clouds during a warmfront
(from front being far away to close)
CI - CS - AS - NS
Which type of front is mostly stable/unstable air?
Coldfront: unstable air
Warmfront: stable air
What’s the relation between air temperature and moister ?
Colder air masses are dryer - warm air masses holds more water
Wind direction behind and infront of a warm front ?
Behind: SW
infront: SE
What characterises a stationary front ?
Clouds and rain for a long time
no movement and upredictable
Cold front occlusion definition
Cold air overtaking the warm front is colder than the air ahead of the warm front
warm front occlusion
In a warm occlusion, the cool air mass overtaking the warm front is warmer than the cold air ahead of the warm front, and rides over the colder air mass while lifting the warm air.
Why is an occluded front considered more complex than the others ?
Because it’s a combination of both frontal weathers
What the most important element of weather usually not found above the troposphere ?
Moister
What’s the standard temperature lapse rate?
2º per 1000’
Cold dense air, lifting warmer less dense air is an example of what type of temperature inversion ?
Frontal
During low pressure the rising air is ____ ? ( warmed/cooled)
cooled
What’s the characteristic of air around a high/low pressure below 2000’ ?
Low pressure - Converge towards
High pressure - Diverge away
What causes winds to flow across the isobars rather than parallel to ?
Surface friction
A large dewpoint spread indicates (high/low) relative humidity ?
low
Which clouds are associated with noctural cooling ?
Low stratus and fog
The frontal inversion of any front always slopes over the ____ and the precipitation associated occurs in the ____ air
The frontal inversion of any front always slopes over the cold air and the precipitation associated occurs in the cold air
The type of air masses most often associated with fronts in the USA are ____ & _____
air mass abbreviations
P & T
What’s the definition of a cold front ?
The leading edge of an advanding mass of cold air
What’s the average speed of a cold front ?
25-30 kts
In which direction does a cold front generally move ?
SE
What’s the flight procedure if in the vicinity of a cold front ?
Land and wait for weather to pass
Define a warm front
The trailing edge of a retreating mass of cold air, with warm air moving in behind the frontal symbol
Warm fronts generally moves to the ____
NE
Where does weather occur in regards to a stable warm front ? (Ahead, behind)
Ahead
What weather hazards could be expected if the warm air being lifted by the warm front is unstable
Embedded thunderstorms and/or CB clouds
What’s important doing preflight planning when flying in the vicinity of a warm front ?
An alternate airport + fuel
A stationary front will normally be more similar to that of a ____ but less intense
Warm front
How does the wind at a stationary front usually flow in relation to the chart symbol ?
Parallel to the frontal symbol
what’s the definition of fog ?
Visible moister with base below 50’ and no visible downward motion
What’s the difference between fog (FG) and mist (BR) ?
Fog: Visibility less than 5/8 SM
Mist: Visibility greater or equal to 5/8 SM
What factors need to be present for fog to occur ?
- Small dew point spread / temperatures
- Abundant condensaton nuclei
- Light surface wind (except 2 types)
- Cooling land surfaces with warm moist air above
How does OVC sky affect fog ?
Prevents fog og lengthen the time it takes to dissapear
Name the types of fog
Radiation fog
Advection fog
Precipitation-induced fog
Freezing fog
Upslope fog
Ice fog
Explain: Radiation fog
Caused by (terrestial) radiation cooling the ground which cools the lower levels of air on clear, calm nights
midnight to sunrise - light winds
Explain: Advection fog
Caused by surface cooling from warm, moist air flowing over (vertically) a cooler surface
3-9 kts winds
Explain: Precipitation-induced fog
Where do we find this type of fog ?
Caused by rain falling through a frontal inversion and saturates the cooler air below = visible moister = fog
Ahead of warm front - behind cold front
Explain: Upslope fog
Caused by moist, stable ar being liftes by sloping terrain
clouds on mountains is also fog - cools adiabatically - wind + 10 kts
Explain: Freezing fog
Fog which is made of supercool droplets.
If thoses droplets get in touch with an object - they’ll freeze.
Fog in negative temperatures
Explain: Ice fog
Fog comprised of tiny ice crystals suspended in the air
temps -30 degreese celcius
When is frost formed ?
Ice crystals formed by deposition of water vapor contacting a cold surface
Cold clear nights
When is rime icing formed ?
when supercooled water droplets contact a surface
When is clear icing formed
When large supercooled water droplets contact a surface
During freezing precipitation
When does freezing rain form ?
When rain droplets fall thru a frontal inversion into a layer of air which has sub zero temperatures
Most common with warm fronts due to shallow slope
What’s the categories of icing intensity ?
Trace
Only hazardous if encountered + 1 hour
(No matter deicing)
Light
May be hazardous if encountered - 1 hour (Not if deicing)
Moderate
Even short encounters are potentially hazardous
(Deicing necessary)
Severe
Deicing can’t control the hazard - diversion necessary
Which 3 factors need to be present for thunderstorms to develope ?
1 Unstable or conditionally unstable air
2 High moister content
3 Lifting action
Name the 3 types of thunderstorms
1 Air mass thunderstorms
(Thermal convective activity)
2 Orographic thunderstorms
(Terrain)
3 Frontal thunderstorms
Types : ( Fast moving cold front creates CB, squall line (CB) created by fast moving cold front, warm front unstable air comes in contact with warmfront slope, Stationary front developed into CBs, Occluded front develope CBs - worst weather, stacked over a spot)
What are the 3 stages of a thunderstorm ?
1 Towering cumulus
2 Mature
(begins when precipitation starts - vertical currents)
3 Dissipating
OWS icing chart
At what altitudes can we expect icing if the following is reported ?
Icing from surface to 3000’ MSL
What hazards for flight follow icing
- Reduction of lift
- Increased drag and weight
- Reduce rotor stall speed
- Reduce visibility on windshield
- Block statis/pitot ports = instrument errors
OWS turbulence chart
At what altitudes can we expect turbulence if the following is reported ?
Surface to 18.000’ MSL
When does microburst most commonly occur ?
Mid summer in the afternoon when high cloud tops are present
What’s the difference between wet and dry microbursts ?
Wet has surface rain
Dry has virga
(“dry storm” = rain falls from sky but evaporates before reaching ground)
What can stationary fronts develope into ?
Frontal waves ( or open waves)
What may frontal waves develope into ?
An Occluded front
If an occluded front symbol is extended from the cold front symbol it is a ____ type occlusion
Cold type occlusion
What’s procedure when flying in the vicinity of an occluded front ?
Circum navigate
What are the dissipation factors for most types of fog ?
- Heating
- Strong winds
- Greenhouse effect / overcast sky
Will an OVC sky slow or speed up the dissipation of fog ?
slow
What’s the difference between clear ice and rime ice ?
The size of the supercooled water droplets
Which intensity of icing would require immediate diversion from the affected altitude ?
Severe icing
Where is freezing rain typically found during winter months ?
ahead of a warm front
Which OWS chart is the only one that shows numbers in thousands of feet ?
“12” on chart = “12.000”
Freezing level chart
Is “small temperature/dewpoint spread” one of the factors needed for thunderstorms ?
Yes - Because a small dewpoint spread = high moister content - which is one of the three factors in creation of thunderstorms
A summertime thunderstorm that occurs every day in the same area is a ____
Air mass thunderstorm (Thermal)
How do you know a thunderstorm is in the mature stage ?
Begins to rain and downdrafts are coming from the cloud
What’s the flight procedure when in the vicinity of a thunderstorm caused by thermal activity ?
Land og circumnavigate
The OWS turbulence chart is drawn for what category of turbulence ?
CAT 2
(Out category as Lakota)
If an aircraft is rated as CAT 3 for turbulence - will the forecasted turbulence on the OWS chart be experienced less of more ?
Less then the severity forecasted
What’s the best conditions for a dry microburst to happen
Time a year, Time a day, cloud type
Hottest part of the year
Hottest time a day
Convective clouds
Eg. July - 14:00 - CU clouds
Who do you contact if your local WX service is closed ?
Military operational weather squadron (OWS) - covering your area
How does a lower relative humidity affect a/c performance ?
Lower RH = Smaller % of moister in air = fewer clouds and better a/c performance
How does a lower relative humidity affect a/c performance ?
Lower RH = Smaller % of moister in air = fewer clouds and better a/c performance
What’s the standard pressure lapse rate with altitude ?
1 Hg per 1000’
If you don’t reset your altimeter setting - what will you TALT be in regard to your IALT ?
Lower
Which air mass code and characteristic does each of the 4 airmasses have ?
What change in wind direction can be expected with a stationary front ?
180 degree change
Which type of front is the stationary front typically more similar to ?
More like the warm front
In flight on your instruments - how would can you see that a front as passed ?
Change in OAT and windshift
If the temperature is decreasing a ____ front has passed
Cold
If the temperature is increasing a ____ front has passed
warm
Occlusions happen when the ____ front catches up to the ____ front
Cold catches the warm
When does frontal waves occur ?
What can it turn into ?
When the cold front and warm front shares the same low pressure
Can turn into an occlusion
What’s the difference between a cold and warm occlusion ?
Cold The cold air overtaking the warm front is the colder than the air ahead of the front and plows underneath both.Warm The cold air overtaking the warm front is not colder than the. air infront and rides over
