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ATPL - BGS [Mod 1] Meteorology > 05. Triggers and Inversions > Flashcards

05. Triggers and Inversions Flashcards

1
Q

Triggers and Inversions

“Air mass is forced up over rising ground, hills or mountains”

This is a definition of what sort of trigger to an air mass initially lifting

A

OROGRAPHIC LIFTING

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2
Q

Triggers and Inversions

“air is heated in the lower layers. This can be from seasonal or daytime heating of the surface, or from local areas that are particularly hot, like factories and power stations”

This is a definition of what sort of trigger to an air mass initially lifting

A

THERMAL

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3
Q

Triggers and Inversions

“where 2 air masses meet at the frontal surface the warmer air will be forced to rise over the colder air”

This is a definition of what sort of trigger to an air mass initially lifting

A

FRONTAL CONVERGENCE

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4
Q

Triggers and Inversions

“surface air is moving so that it converges, the only way out is up, so low-level winds coming together is always associated with rising air and convection”

This is a definition of what sort of trigger to an air mass initially lifting

A

NON-FRONTAL CONVERGENCE

  • REMEMBER Difference is the mention of low level winds coming together, not air masses

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5
Q

Triggers and Inversions

“a specialised form of lifting caused by strong winds at low levels or on the lee side of mountains”

This is a definition of what sort of trigger to an air mass initially lifting

A

TURBULENT LIFTING

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6
Q

Triggers and Inversions

Air that is absolutely unstable where oragraphic lifting is triggered will rise until the due point. If the air is unsaturated, cloud may never form, but the convection still exists. This is known as what thermals

A

BLUE THERMALS

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7
Q

Triggers and Inversions

If a mountain triggers oragraphic lifting and the air is absolutely unstable, the air will CONTINUE TO RISE or SINK ON THE LEESIDE at the top of the mountain

A

CONTINUE TO RISE

  • Air that is unstable will want to continue to rise away from where it was before
  • Air that is stable wants to return to where it was before, so will sink

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8
Q

Triggers and Inversions

If a mountain triggers oragraphic lifting and the air is absolutely stable, the air will CONTINUE TO RISE or SINK ON THE LEESIDE at the top of the mountain

A

SINK ON THE LEESIDE

  • Air that is unstable will want to continue to rise away from where it was before
  • Air that is stable wants to return to where it was before, so will sink

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9
Q

Triggers and Inversions

If a mountain triggers oragraphic lifting and the air is absolutely stable, if the air is cooled to the dew point, what will occur on the mountain top

A

CLOUDS FORMED

  • Stratiform cloud is formed i.e. thin layer but broad covereage
  • However, if wind aloft pushes this, the clouds may take on other shapes i.e. lenticular clouds etc..
  • Cap cloud - this is cloud that sits over the top of a mountain

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10
Q

Triggers and Inversions

If air is forced to rise oragraphically and the ELR is conditionally unstable, the air will first rise at the DALR or SALR. Once the dew point is reached, the air if it continues to rise will now rise at the DALR or SALR. The air will not become unstable until such time the rising air crosses the DALR or SALR or ELR

A
  1. DALR
  2. SALR
  3. ELR

EXAMPLE

  • In theory, where the air mass strats to cool from the DALR to the SALR (dew point) signifies the cloud base
  • As the air cools at the SALR and continues to rise, until it crosses back over the ELR, cloud will form. The cross over points signify the cloud base and cloud tops
  • In the diagram, mountain 1 (smallest), air will be forced up but sink back down
  • In the diagram, mountain 2 (medium), air will be forced up and cool to dew point, causing cap cloud
  • In the diagram, mountain 3 (largest), air will be forced up. Cloud starts to form on the windward side. If it continues to be forced up, cumulous clouds start to form into the higher altitudes

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11
Q

Triggers and Inversions

The size of the orographic trigger will determine what in relation to air masses being lifted over mountains

A

HOW CONDITIONALLY UNSTABLE

EXAMPLE

  • Passing the small mountain, air will not colld enough to form cloud, nor will it be unstable, so it will sink back down the downwind side
  • Over the second mountain, the air rises high enough to form cloud, but remains stable, and sinks back down forming “cap” cloud
  • Over the third and largest mountain, cloud forms. The air goes unstable and cloud continues up to the highest available level.

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12
Q

Triggers and Inversions

When conditionally unstable air is forced to lift orographiacally over mountains, and the air is more moist, this will INCREASE or DECREASE the likliehood of the air being forced towards instability.

This will result in HIGHER or LOWER cloud bases and HIGHER or LOWER cloud tops

A
  1. INCREASE
  2. LOWER
  3. HIGHER

EXAMPLE

  • Adding moisture to a conditionally unstable air mass increases its tendency towards instability, and in unstable air masses moist air gives lower cloud bases and higher tops

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13
Q

Triggers and Inversions

When the air near the surface is heated by CONVECTION or CONDUCTION and by radiation, this will trigger what sort of lifting of the air

A
  1. CONDUCTION
  2. THERMAL

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14
Q

Triggers and Inversions

Where the air is heated near the surface through conduction and radiation, and lifting occurs, cloud or blue thermals will form according to the level of what in the air

A

WATER CONTENT

  • Cloud forms when the air becomes saturated when it reaches dew point
  • If the air is unsaturated at the dew point, clouds will not form but will create blue thermals
  • If the air is saturated at the dew point, clouds will form

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15
Q

Triggers and Inversions

Heating of the surface during the day will lead to LOWER or HIGHER cloudbase

A

HIGER

  • Refer to the Thermal graph that reflects that the temperature lines/curves move further to the right as the ground temperature warms
  • As air rises, it does not reach the ELR before it reaches the dew point
  • Clouds therefore start to form higher
  • The air is cooling at the SALR but still warmer than the ELR
  • This means the SALR is to the right of the ELR, meaning insability

EXAMPLE

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16
Q

Triggers and Inversions

Heating of air at lower levels is a very powerful factor at making air masses STABLE or UNSTABLE

A

UNSTABLE

  • Refer to the Thermal graph that reflects that the temperature lines/curves move further to the right as the ground temperature warms
  • As air rises, it does not reach the ELR before it reaches the dew point
  • Clouds therefore start to form higher
  • The air is cooling at the SALR but still warmer than the ELR
  • This means the SALR is to the right of the ELR, meaning insability

EXAMPLE

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17
Q

Triggers and Inversions

What weather phenomina over India is an example of a particularly unstable air system caused by orographic lifting

A

SOUTHWEST MONSOON SEASON

  • warm tropical sea air picks up a lot of moisture
  • wind moves inland and being heated from below
  • The moutains of the Western Ghats force orographic lifting, which results in the biggest convective clouds in the world
  • Cloud tops reach 55,000ft

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18
Q

Triggers and Inversions

Where two fronts meet, if one front is cold and the other warm, what will happen to the warmer air

A

FORCED UP AND OVER COLDER AIR

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19
Q

Triggers and Inversions

If a front is moving more rapidly, the uplift will be MORE or LESS intense

A

MORE

  • Cold air will force warm air up faster

FRONTAL ASCENT

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20
Q

Triggers and Inversions

Trade winds converge at a line known as the what

A

INTER-TROPICAL CONVERGENCE ZONE
(ITCZ)

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21
Q

Triggers and Inversions

Where air masses of no significant differences of temperature meet as a result of the low level winds converging them together, they will be forced to rise. This will bring STABLE or UNSTABLE air masses

A

UNSTABLE

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22
Q

Triggers and Inversions

Air masses converging together at the surface are linked with what sort of pressure system

A

LOW PRESSURE

  • Air masses converge together
  • They are forced to rise, cooling as they do
  • Air aloft will then want to sink back down, so move to a high pressure system where it then sinks back to the surface
  • Air associated with a high pressure system will therefore diverge at the surface

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23
Q

Triggers and Inversions

Air masses diverging at the surface are linked to what sort of pressure system

A

HIGH PRESSURE

  • Air masses converge together
  • They are forced to rise, cooling as they do
  • Air aloft will then want to sink back down, so move to a high pressure system where it then sinks back to the surface
  • Air associated with a high pressure system will therefore diverge at the surface

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24
Q

Triggers and Inversions

Turblance on the lee side of a mountain can only happen when the air mass is STABLE or UNSTABLE

A

STABLE

  • If the air mass were unstable, then when triggered by the orographic lifting, it would continue to rise
  • When the air is stable, it wants to sink back down.
  • In order for the turbulent air to exist on the leeside, the air must therefore be sinking, so must be stable

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25
Q

Triggers and Inversions

In order for turbulence to be produced on the leeside of a mountain with a stable air mass i.e. the air mass has a ELR lapse rate of less than SALR (1.8℃ per 1000 ft), the air must also be DRY or MOIST and have HIGH or LOW wind speeds

A
  1. MOIST
  2. HIGH

  • The effect of turbulence only occurs if the air mass is stable i.e. ELR less than SALR, and the air must be moist and there must be high wind speeds

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26
Q

Triggers and Inversions

  1. Turbulent mixing on the leeside of a mountain will cause cooler air aloft to be forced down to the surface. As it descends, the air will warm at the DALR or SALR.
  2. The turbulent mixing will then force the air at the surface, which is warming, back up to a higher altitude aloft, where it will cool at the DALR or SALR.
  3. This process mixes the air up, causing the a HIGHER or LOWER or AVERAGE temperature to be achieved
  4. This will now cause the ELR to correspond with the *DALR or SALR

DIAGRAM

A
  1. DALR
  2. DALR
  3. AVERAGE
  4. DALR

  • Air at A will be taken down by the turbulence to B
  • Air will warm at the DALR as it descends.
  • Air at C will be taken up to the turbulence to D
  • Air will cool at the DARL as it rises
  • After a time, everything has been mixed up and the air mixture will take an average temperature
  • The turbulent mixing changes the structure of the air mass within the turbulence layer
  • Air aloft is now half way cooler than it was before
  • Air at the surface is half way warmer than it was

DIAGRAM 01
DIAGRAM 02

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27
Q

Triggers and Inversions

Turbulent mixing requires strong wind and the air mass to be stable. If the air is moist and turbulent mixing takes place on the leeside of the mountain, what sort of clouds may form

A

LENTICULAR

  • if an air mass is moist and turbulent mixing taking place, additional cooling in the top half of the turblence layer will produce cloud
  • The cloud will have a high kinetic energy content in the turbulence, making it persistent
  • Sheets of turbulence cloud with sharply defined top will go on for miles and miles downwind
  • Lenticular clouds

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28
Q

Triggers and Inversions

Turbulent cloud layers on the leeward side of the mountain will be SHALLOWER or DEEPER during the day than the night

A

SHALLOWER

  • Turbulence cloud layers get deeper during the night as temperature fall

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29
Q

Triggers and Inversions

Where turbulent mixing takes place, the air above the turbulence layer remains uneffected. As a result, this means there is a sharp rise in temperature (given that the ELR is uneffected, and in the turbulent layer it has been made the same as the DALR). Given the sharp rise in temperature, this means that there is a what above the turbulence layer

A

INVERSION

INVERSION

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30
Q

Triggers and Inversions

“the process of dealing with the changing tempreature of a parcel of air due to the air rising or sinking, and assumes no heat, mass or momentum pass across the air parcel boundary”

This is a definition of what process

A

ADIABATIC

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31
Q

Triggers and Inversions

“any temperature change of air not related to its adiabatic vertical displacement”

This is a definition of what process

A

DIABATIC

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32
Q

Triggers and Inversions

Which of the following are adiabatic cooling processes;

[ ] Convection due to heating of the ground
[ ] Convection due to cold air passing over warm surface
[ ] Mixing of air of different temperatures
[ ] Convection due to convergence i.e. sea breeze convergence boundary
[ ] Convection due to convective instability aloft
[ ] Fog i.e. radiation fog and advection fog
[ ] Turbulent mixing in the boundary layer
[ ] Forced lifting by orographic ascent
[ ] Forced lifting by frontal ascent
[ ] Rotational pressure reduction i.e. tornado

A

[X] Convection due to heating of the ground
[X] Convection due to cold air passing over warm surface
[ ] Mixing of air of different temperatures
[X] Convection due to convergence i.e. sea breeze convergence boundary
[X] Convection due to convective instability aloft
[ ] Fog i.e. radiation fog and advection fog
[ ] Turbulent mixing in the boundary layer
[X] Forced lifting by orographic ascent
[X] Forced lifting by frontal ascent
[X] Rotational pressure reduction i.e. tornado

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33
Q

Triggers and Inversions

Which of the following are diabatic cooling processes;

[ ] Convection due to heating of the ground
[ ] Convection due to cold air passing over warm surface
[ ] Mixing of air of different temperatures
[ ] Convection due to convergence i.e. sea breeze convergence boundary
[ ] Convection due to convective instability aloft
[ ] Fog i.e. radiation fog and advection fog
[ ] Turbulent mixing in the boundary layer
[ ] Forced lifting by orographic ascent
[ ] Forced lifting by frontal ascent
[ ] Rotational pressure reduction i.e. tornado

A

[ ] Convection due to heating of the ground
[ ] Convection due to cold air passing over warm surface
[X] Mixing of air of different temperatures
[ ] Convection due to convergence i.e. sea breeze convergence boundary
[ ] Convection due to convective instability aloft
[X] Fog i.e. radiation fog and advection fog
[X] Turbulent mixing in the boundary layer
[ ] Forced lifting by orographic ascent
[ ] Forced lifting by frontal ascent
[ ] Rotational pressure reduction i.e. tornado

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34
Q

Triggers and Inversions

What are the 3 methods of cloud dissipation

A
  1. TEMPERATURE INCREASING
  2. CLOUD MIXING WITH DRIER AIR
  3. AIR SINKING WITHIN THE CLOUD

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35
Q

Triggers and Inversions

Why does increasing temperature help to dissipate cloud

A

WARMER AIR HAS HIGHER CAPACITY TO EVAPORATE LIQUID WATER

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36
Q

Triggers and Inversions

  1. When a cloud is no longer developing and not adding additional condensational moisture, drier environmental air will do what to a cloud to help dissipate it.
  2. As a result, this will give the cloud what sort of appearance
  3. This process is called what
A
  1. ERODE THE CLOUD
  2. WISPY EDGES
  3. ENTRAINMENT

  • An example is cirrus clouds near the jet streams where the clouds become very wispy

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37
Q

Triggers and Inversions

Why does the air sinking help to dissipate cloud

A

AIR WARMS ADIABATICALLY
WARM AIR HAS A HIGHER CAPACITY TO EVAPORATE LIQUID WATER

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38
Q

Triggers and Inversions

If an aircraft is climbing from an airfield that is in a cold air sector and flys through a warm front, what temperature phenomena would you experience

A

TEMPERATURE INVERSION

  • Cold air is cooling at a specific lapse rate
  • As the aircraft hits the warm front, there is going to be a sharp rise in air temperature
  • However, as the aircraft continues to climb, the warmer air in the warm front is still cooling with altitude

FRONTAL INVERSION

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39
Q

Triggers and Inversions

“When two dissimilar air masses meet and the warm air settles overhead the cold air, the OAT will rise at the frontal surface”

This is the definition of what sort of inversion

A

FRONTAL INVERSION

FRONTAL INVERSION

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40
Q

Triggers and Inversions

What are the 4 ways in which inversions form

A
  1. FRONTAL
  2. SURFACE COOLING
  3. SUBSIDENCE IN STABLE AIR
  4. TURBULENCE

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41
Q

Triggers and Inversions

“The ground surface is cold i.e. during the night or during winter season, the air in the lower layers will be cooled by conduction. Cooling from below makes the air mass more stable.”

This is the definition of what sort of inversion

A

SURFACE COOLING

SURFACE COOLING

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42
Q

Triggers and Inversions

“air rising in one place is balanced by air in another that is warming as it descends at the DALR, raising the temperature aloft. This inversion typically starts at high levels and gradually sinks”

This is the definition of what sort of inversion

A

SUBSIDENCE
(in stable air masses)

SUBSIDENCE INVERSION

18

43
Q

Triggers and Inversions

“Warmer air aloft is brought down to the surface. Cooler air at the surface is taken aloft. As the air mixes, it eventually averages out, and the ELR has the same lapse rate as the DALR. In layers of air above, the ELR remains uneffected, causing a sharp rise in temperature”

This is the definition of what sort of inversion

A

TURBULENCE

TURBULENCE INVERSION

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44
Q

Triggers and Inversions

A dry stable air mass has an ELR of 1.5℃/1000 ft, and a surface OAT of 15℃. A turblence layer forms in the lee of the hills, the top of the turbulence layer is at 3000 ft. What will be the new surface OAT, and the OAT in the top of the turbulence layer be

A
  1. SURFACE: 17.25℃
  2. TOP OF LAYER: 8.25℃

ANSWER

  • REMEMBER the air is circulating up and down at first before averaging out - see diagram 1 and diagram 2
  • Air moves from A to B and from C to D, cooling at the DALR of 3℃ per 1000 ft and the ELR of 1.5℃ per 1000 ft
  • Eventually, the temperatures even out

Step 1 - CALCULATE ELR LIFT
* The surface temperature is 15℃
* The lapse rate of ELR is 1.5℃ per 1000 ft, and the turbulence layer is 3000 ft.
* 1.5℃ x 3 (3 times 1000 feet) ⋉ 1.5 x 3 = 4.5
* 15℃ - 4.5℃ = 10.5℃

Step 2 - CALCULATE DALR LIFT
* The surface temperature is 15℃
* The lapse rate of the DARL is 3℃ per 1000 ft and teh turbulence layer is 3000 ft
* 3℃ x 3 (3 times 1000 feet) ⋉ 3 x 3 = 9
* 15℃ - 9℃ =** 6℃**

Step 3 - CALCULATE DALR DESCEND
* Air lifting at the ELR will not cool as much as the air lifted at the DALR
* The warmest temperature reached at the top of the turbulence layer is 10.5℃, as calculated in step 1
* This air will warm as it descends, the most being the DALR, which is 3℃ per 1000 ft
* 10.5℃ + (3℃ x 3 [3 times 1000 ft]) ⋉ 10.5 + (3 x 3)
* 10.5 + 9 = **19.5℃ **

step 4 - CALCULATE NEW OAT
* The coldest air at 3000 ft is 6℃, the warmest is 10.5℃
* To calculate the average, add together and divide by 2
* 10.5 + 6 = 16.5
* 16.5 / 2 = 8.25℃

  • The coldest air at surface is the original OAT 15℃, the warmest is 19.5℃
  • 15 + 19.5 = 34.5℃
  • 34.5 / 2 = 17.25℃

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45
Q

Triggers and Inversions

When calculating the new ELR of a turbulence layer on the lee side of a mountain, you work out the average temperature at the surface and at the top of the turbulence layer to get the new OAT at the surface and at the turbulence layer top.

REMEMBER Once the temperature is averaged out, the ELR becomes the DALR in the turbulence layer, so when the air rises above the ceiling, it wil move into air unimpacted by the turbulence layer, where the air cools at the original ELR rate.

What is the equation to determine what the difference is between the air rising above the turbulence layer, in which the ELR has become the same as DALR i.e. 3℃ per 1000 ft, and the ELR above the turbulence layer, where it is unaffected and as such, an inversion occurs

A

(DALR - ELR) x HEIGHT OF TURBULENCE LAYER / 2

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46
Q

Triggers and Inversions

“radiation cooling of the air on a clear night on the valley sides which produces cold air that slides down into the valley bottom”

This is the definition of what effect

A

KATABATIC

  • Cold air pooling at the bottom of the valley causes a temperature inversion
  • The warmer air sits on top of the cold air at the bottom

VALLEY INVERSION

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47
Q

Triggers and Inversions

Warm air above cold air acts like a lid. This prevents the rise of pollutants from lower levels and creates a layer of what

A

HAZE

  • Reduced visibility due to pollutants and particulats being held down by the lid of warm air

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48
Q

Triggers and Inversions

An aircraft climbing from an airfield that is sat in cold air and passes through a temperature inversion will see an INCREASE or DECREASE in the ROC, and an INCREASE or DECREASE in airspeed

ROC - Rate Of Climb

A
  1. REDUCTION
  2. DECREASE

  • The colder air is more dense so offers better performance to the engines
  • As the aircraft breaks into the warm air, the air becomes less dense, so if the engines remain at the same thrust setting, there is less being produced
  • Less thrust means less lift, so reduced ROC, and less thrust means less forward momentum, so less airspeed
  • Inversley;
  • The warmer air gives less performance to an aircraft descending, so more thrust will be applied
  • When the aircraft breaks through into the colder air, this air is more dense
  • If the same thrust settings are maintained, the aircraft will start to perform better
  • Therefore, more thrust is achieved for the same setting, which means that forward velocity is increased aka more airspeed

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49
Q

Triggers and Inversions

An aircraft descending to an airfield that is sat in cold air and passes through a temperature inversion will see an INCREASE or DECREASE in the ROD, and an INCREASE or DECREASE in airspeed

ROD - Rate Of Descent

A
  1. INCREASE
  2. INCREASE

  • The colder air is more dense so offers better performance to the engines
  • As the aircraft breaks into the warm air, the air becomes less dense, so if the engines remain at the same thrust setting, there is less being produced
  • Less thrust means less lift, so reduced ROC, and less thrust means less forward momentum, so less airspeed
  • Inversley;
  • The warmer air gives less performance to an aircraft descending, so more thrust will be applied
  • When the aircraft breaks through into the colder air, this air is more dense
  • If the same thrust settings are maintained, the aircraft will start to perform better
  • Therefore, more thrust is achieved for the same setting, which means that forward velocity is increased aka more airspeed

VALLEY INVERSION

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50
Q

Triggers and Inversions

How are inversions cleared

A

HEATING BELOW

23

51
Q

Triggers and Inversions

What cloud type will be common with a temperature inversion

A

STRATIFORM

  • Thin layer, spread out. The air cannot rise more because of the temperature inversion but may reach its dew point causing long flat, spread clouds to form

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52
Q

Triggers and Inversions

Stratiform cloud development are often seen over what sort of ocean type (in terms of temperature)

A

COOL OCEAN

  • The cool ocean cools the air in contact with it. If air aloft is warmer, an inversion occurs
  • The air is very moist because of the sea, therefore as it cools, it is likely to reach the dew point
  • Clouds will then form, the inversion acts like a lid, keeping the cloud spread and thin - stratiform

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53
Q

Triggers and Inversions

Fog is more likely to form on CLEAR or CLOUDY nights

A

CLEAR

  • Surface temperature is able to radiate away as no clouds keeping the heat in a lower layer
  • As air in touch with the cold surface cools, it may reach the dew point, so fog will form

24

54
Q

Triggers and Inversions

Fog formation as a result of a temperature inversion i.e. where the night is cloudless, the surface radiates its heat away, and the air in contact cools past dew point, is very common in what latitudes

A

HIGHER LATITUDES

24

ATPL - BGS [Mod 1] Meteorology (27 decks)

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