Initial Flashcards
What is the mix of gases in the atmosphere?
78% Nitrogen
21% Oxygen
1% mix of gases
What are the layers of the Atmosphere?
Troposphere
Tropopause
Stratosphere
Mesosphere
Mesopause
Thermosphere
What is the altitude and temp for the top of the Tropsphere / Tropopause
11km average
8 at the poles
11 mid regions
16 equator
-56.5c
What is the difference between heat and temperature?
Heat is an energy source, measured in Kj or calories
Temperature is the measure of heat in a system.
What is specific heat?
The amount of energy required to raise the temp of 1 kg of mass by 1 C
Water has a higher Specific Heat than Air, which is higher than rock
AKA - ability to store heat
What thermometers are used to measure surface air temp?
Mercury - most common. But Freezes at -38c
Alcohol - freezes at -112c
Bi-metal
Electronic Senors - these need to be calibrated to mercury thermometers on a regular basis
What is a Stevenson box?
A meterology measuring station.
- 1.5 meters of the ground
- Over grassy areas
- protected from direct things such as wind or solar rays
Note: these are usually more accurate in the mornings.
Also don’t measure the air temp on a runway….
How is information gathered for meterology reporting?
abc
Stevenson box
Radiosondes - measures pressure, humidty, temp, wind - attached to a balloon
Satelites
Airtraffic in flight ( both manual and automatic )
Why does temperture matter with regards to the Tropopause?
Temp changes the height of the Tropopause.
How does the sun heat earth?
Sun emits Shortwave radation
It does not heat the lower 10km.
The earth warms up, depending on the surface.
What is Albedo?
The amount of energy reflected back into space.
Conduction vs Convection vs Avection?
Conduciton - warm ground transferring heat into the air.
Convection - rotating hot air and cold air. Usually topped by Cumulus clouds
Avection - sideways movement of air mass ( heat, vapour etc )
What heat does the earth emit?
How is this kept ‘in’?
Long wave radition
Water vapour absorbs the heat.
This means heat coming in from the sun during the day is largely kept at night ( shortware from sun, long wave from earth ).
Greenhouse.
What is inversion?
Where the temp increases with Altitude.
Surface Inversion:
- Polar regions ( ground is cold )
- Valleys and basins, cold air flows down. This causes low level fogs
Avection - warm air is carried from another place.
What is a Isothermal Layer?
Where the temp does not change with altitude.
What is the daily variation ( degrees c ) and why?
Heating is based on heat coming in vs going out.
During the day, solar radition is more than terrestial radition = heating up.
At night, terresterail is more than solar = cooling down.
How does the daily variation change by latitude ( and why )
In the equator - higher daily variation
At the poles - lower daily variation
This is because the solar ration is ‘spreadout’ due to the sloping of the surface.
How does the annual variation change by latitude ( and why )
Equator - only 5 degrees annually
Higher lattitudes = much more variation.
Why?
Due to the tilt of the earth. In winter the solar radtion is much more dispersed.
Why is the annual/daily variation over ocean much lower?
Water has better heat absorbation. This means that more heat is absorved, over a larger area - resulting in little terretial radation.
Why are deserts hotter ( at the same latitude )
Over 50% of solar radition is used for evapouration. In deserts there is less mositure. Resulting in higher temps AND wider variations
What does snow do to temp variations?
Snow reflects more heat AND acts as a blanket. So snowy areas are colder close to the surface and tend to have less variation
What is colder - the Artic or Antarctica ( and why )
Antarctica
In the artic, it’s floating ice - and the water has a moderating effect. Antarctia is a contentiant.
This is also why Siberia is colder than the Artic, despite being closer the equator
What is a Barograph?
A barometer that measures and plots pressure over time.
Usually a Aneroid or Electronic tool.
What are the different types of units to measure pressure ( and conversation factors )
hectopascal ( hPa ) = 1 millibar (mb )
750 mm Hg
29.53 inches Hg
What is QFE and 2 ways to calculate it?
pressure at a given altitude ( airport ).
1. Take the height, divide by 27 and subract that amont from 1013. ( we are using standard lapse )
2. At the airport adjust the baro knob on the altimeter so that the altitude reads 0
3.
How does the air temp affect the rate in DECREASE of pressure?
Colder air has higher rates of decrease
How does temp. affect the vertical distrances between pressure levels?
Cold air has smaller vertical distances that hot air
What does a pressure ( weather ) chart show?
How often is it updated?
What are the pressure intervals?
Pressure, corrected to MSL
Updated every 3 hours
Pressure intervals are 2 or 4 hPa
What is an isobar?
Points of equal pressure
What are the 6 types of pressure systems?
- Low ( Depression ) - can develop into cylones
- Seconday Low
- Trough - extended low pressure
- High ( Anti cyclone )
- Ridge - extended high pressure
- Col - equal point between two highs and lows
What is the pressure gradient?
Difference in pressure / distance
Shown by isobars being close together
A high pressure gradient usually brings high winds
What is trough?
Elogated parts of low pressure
What is a col?
A neutral area between two ‘High’ pressure areas and two ‘Low’ Pressure areas where the wind is very light or calm.
What is QFF
Estimated pressure at sea level.
This is what is used on a pressure ( weather ) chart
What is an Isotach?
Joining all places with equal windspeed
What is the pressure lapse rate?
1 hPa per 27 feet
Difference and uses for
* QFE setting
* QNH setting
* QNE setting
QFE - makes the altimeter read in feet above the airport. Used in training and some military operations
QNH - normal. Set altimeter so that the altitude reads airport elevation
QNE - for use above transistion altitude (13,000 ft to FL150
With Wind, what is veering and backing?
- Veering - wind changing direction in a clockwise manner
-
Backing - anti clockwise direction
*
How is wind strength shown on a chart?
- 1/2 rod = 5 kts
- 1 rod = 10 kts
- 1 triangle = 50 kts
*
What causes gusts and lulls, and when do they happen?
Near the ground
Ground Features
Difference in radition aborbisation
How is wind measured?
And pros and cons
The name of the ground based instrument
Anometer
Place in the open 10m off the ground
Does not measure gusts well, slow to react
What is a an Anemograph?
What is the average time that wind is measured over?
Measures winds and plots it on a graph
Not good in light winds
2 - 10 minutes
How are upper winds measured ( 3 ways ) AND put on a chart?
- Balloons
- Satelites ( looking at movement of water features, such as clouds )
- Aircraft reports
They are put on a chart at a given flight level
In a Metar what does VRB mean in the wind section?
E.G
METAR NZAR 060600Z AUTO VRB10KT // 24/17 Q1018
The wind direction can not be established.
In a Metar - how is wind direction given?
And what is the time that the wind is measured over?
E.G direction
degrees in True north
Wind is averaged based on the conditions over the preceding 10 minutes.
When is an additional section given in a Metar for wind direction?
If the wind direction varies by more than 30 degrees, this will be added after the wind.
What are the normal strenght wind socks?
And how can we tell strenght?
15kt and 25kt
When flying what are 8 ways to tell wind direction?
Smoke - gives clear information on direction
Dirt - clear information on direciton
Cloud shadows
Wind Ripples on water
Tree Tops
Wind shadows
Wind Lanes
Aircraft Drift
Wind Ripples - how can we tell strength AND what are disadvantages?
white caps appear at 7 - 10 kts
They can be hard to see at altitude
When using cloud shadows to find wind direction and strenght, what do you need to be aware of?
It is showing the conditions at the cloud’s altitude - which probably is different to the ground conditions
What is a squall?
A gust of wind that last for serval minutes.
Usually as part of a cold front, bringing rain.
When using aircraft drift to judge wind, what do we need to be aware of?
The wind at the surface will be different that at altitude
Drift can be induced if flying out of balance
It take experience to be able to really read the wind
What does the Pressure Gradient do a parcel of air?
The Pressure Gradient causes the air to begin to flowing from high to low.
As the air flows from High to Low Pressure, what happens to the pressure gradient?
As the air evens out, the pressure gradient lessens.
Pressure graidents cause air to flow, but why does the air rotate?
The corolis affect.
It only acts on moving air.
It acts at 90 degrees to the movement
What impact does the Corolias effect have on air flows in the Northern vs Southern hemisphere?
High Pressure - air flows anticlock wise in the Southern Hemisphere and Clockwise in the Northern Hemisphere
Low Pressure - air flows with earth’s rotation, so Clockwise.
Where is the impact of the corolis force the most and least?
At the equator the least.
At the poles the most.
Due to difference in rotation speeds over the latitude being measured.
If the corolis effect causes rotations further from the equator, what happens to air flowing across the equator?
It does not bend, it flow up into the atmosphere.
What are the main properties of the corolis effect?
Applies force at 90 degrees to travel
Is larger at the poles than equatoor
The corolois effect causes wind to deflect which way at the poles?
( north and south )
North to the right
South to the left
Note: It’s always in the direction of the earth rotation.
What causes wind to flow anti-clockwise in the southern hemisphere?
Corolis Effect
Due to the pressure gradient the air will start moving from high to low
As the wind spead increases, the corolis effect gets strong, bending the wind.
What is a Geostropic wind? ( and cause )
Straight Line Isobars.
Caused because the pressure graident = Corolis effect
What is graident wind?
More normal. Isobars bend.
Corolis effect is greater than the Gradient pressure
What is Buys Ballot Rule?
And how can we use it?
In the southern hemisphere, wind on our back will mean low pressure is on the right.
If the aircraft has left drift ( wind from right ) flying toward a lower pressure.
How does sun up vs sun down affect backing and veering
( and why )
Night Time
Denser air = more surface friction = slower winds.
This makes the winds veer ( adjust clockwise )
Day Time
Less dense air = less surface friction = faster winds.
This makes the winds back ( adjust anit-clockwise )
What is the impact of altitude on wind strenght?
( and other things )
At 3000ft there is zero surface friction.
Means the wind moves faster.
Results in differing wind speeds, slower closer to the surface
The direction will change too. As we descend, wind is slower therefore the winds will veer ( clockwise adjustment )
Does a High converge or diverge?
( and what does this mean )
In a high pressure, the winds diverge at low altitude.
This means that generally, the weather is better - as the winds disperse clouds. Due to adibatic warming.
Does a Low converge or diverge?
( and what does this mean )
In a low pressure system, the winds converges as low altitudes and diverges as it moves up.
This tends to form clouds as moisture is lifted and cooled.
What is a “Dirty High”?
A high moves in, creating an inversion.
This results in low cloud that is ‘trapped’
What is
Saturated Air vs
Unsaturated Air vs
Super Saturated?
Saturated Air - holds all the water vapour that it can.
Unsaturated Air - not yet saturated
Super Saturated Air - saturated air that is cooled down.
What is Dewpoint?
The tempature at which a parcel of air will become saturated at the current pressure.
How are clouds formed ( with regards to dew point )
As a parcel of air rises, the temp goes down, as does the Dewpoint
At the point the dew point and temp meet clouds will form
What can cause air to become saturated ?
(2 methods )
Cooling
- contact with cold surface
- radition
- expansion of lifted air
Addition of moisture
- contact with liquid surface
What factors affect the evaporation rate?
- Wind spped
- Temp Difference between the air and water
- Split between Air temp and Dew Point
When does condensation happen?
What are the effects
To do with storms?
Condensation happens at saturation
This releases latent heat, which can result in thunderstorms and tornados
When can condensation form on the aircraft windscreen?
And why
Condenstation forms on a surface when the surface is cooler than the air.
So a rapid descent
OR in some cases a rapid ascent through an inversion
How does vapour turn to droplets?
At saturation.
A particle is required to form the nucleus
This comes from Smoke, Dust etc
This droplets results in haze.
What is it called if vapour is turned to or from ice?
Sublimation - vapour to ice
Deposition ( desublimation ) - ice to vapour
Deposition is why frost occurs.
What is adebatic cooling and heating?
Why does it happen
It is cause as the parcel of air expands and contracts
Going up = heat created due to lowering pressure.
Coming down = heat absorbed.
What are the 3 ways of measuring humidity?
Mixing Ratio - does not vary with temp.
Relative Humidity - 100% = saturated. Varies with Temp.
Dew point / air temp split - Another measure for relative humidity, but more helpful for pilots.
What is Adiabatic heating and cooling?
And which is which?
As a parcel of air rises, the pressure decreases. This means the parcel of air is reducing in temp.
As a partical of air descends the pressure increases resulting in the parcel of air increasing in temp.
What is the DALR?
Dry Adiabatic Lapse Rate
3 degrees/1,000ft
What is the SALR?
Saturated Adiabatic Lapse Rate
Varies, but at sea level is 1.5c / 1,000ft
What is the ELR?
Environmental Lapse rate
The actual observed temp. decrease as altitude increases.
How do vertical clouds form?
As the parcel of air is rising, it decreases at the DALR, unitl it meets the dew point. Forming the base.
From here the temp of the parcel of air descreases at the SALR.
What are the types of vertical Stability AND the conditions that affect it?
Depends on:
- temp of the parcel air compare to surounding air. - humidity.
- Environmental Lapse rate
Stable - parcel of air resists displacement, and returns if moved.
Unstable - continues to rise of fall until stable conditions are met.
Neutral - if moved, will rest at the new position.
What is an inversion?
A layer of warm air occurs on top of cooler air.
What is an isothermal layer?
There is an area of altitude which has the same temparture.
What conditions causes a Stable Atmosphere?
Relationship between SALR / DALR / ELR
Parcel of air is cooler than surrouding air.
So the
ELR < SALR ( and therefore the DALR too )
What conditions causes an Unstable Atmosphere?
Relationship between SALR / DALR / ELR
If the ELR > SALR - results in unstable conditions
Because as the air is pushed up, it continues to move upwards.
What conditions causes an Conditional Instability Atmosphere?
Relationship between SALR / DALR / ELR
If the ELR is between the DALR and SALR
This means that as the parcel of air rises and hits dew point, then it will start to fall again.
What are the 4 causes of inversions?
Subsidence
Radiation - early morning
Turblent inversion - following radition inversion
??
What are the causes and symptoms of Subsidence Inversion?
- As a parcel of air is falling, warms at DALR of 3c
- Stops at 2,000 ft
- Cloud top spread out at the inversion, resulting in stratus or stratus cumulus clouds
- Haze below the inversion.
What is the symptom and cause of radition inversion?
Conditions needed:
* Clear night
* Low winds ( 6 - 8 kts )
Overnight the air at the surface cools faster than air higher up, due to contact with the surface.
Usually occurs over land or swamp, not oceans or lakes
At sunrise fog often occurs
Windshear is often present at the transistion layer.
What causes a Tuburlance Inversion?
Can occur after a radition inversion.
Frontal Inversion
This occurs when a cold air mass pushes under a warm air mass
Cold side: Cumulus and Towering Cumulus
Warm Side: Cumulonimbus, Cirrus, Cirrostratus
What is the Feohn wind, when does it occur and why?
A warm wind on the lee side of mountains.
Occurs because there are wet parcels of air on the wind side, pushed up the side with the wind.
As they rise, the temp drops as per the SALR (1.5c), resulting in clouds forming
On the lee side, the air is dry, so it warms at the DALR ( 3c) meaning the air is a lot warmer, resulting a warm wind.
What is advection?
Horitonzal movement of air parcels
How does temp affect the SALR?
The rate gets lower and lower temps.
What are the 3 families of Cloud ( by altitude )
Cirrus - > 16,500 ft only has ice crystals, indicator of fronts
Stratus - < 6,500 ft hides the sun
Cumulus - puffy with vertical height.
What does Nimbo or nimbus mean?
E.G Nimbostratus
rain bearing.
What does Alto mean?
E.G Altostratus
Clouds at the mid level
Terms to describe clouds by shape are:
Fractus - ragged shape
Castellus - row of turrets
Cirrus Avaticus - indicator of high humidty at crusing level
What do Fratcus clouds look like?
Ragged, usually at the Stratus or Cumulus level
What is the condensation level?
The level at which the cloud reaches saturation ( temp = dew point ).
As the air rises, it will condensate.
How can we calculate the cloud base, given the dew point and temp at ground level?
The cloud base is the intersection of the DALR (3 per 1000ft) with the Dew Point (0.5 per 1000 ft )
What makes a cloud shallow or tall?
The cloud will form for as long as the ELR < SALR
Shallow clouds - form in stable air ( the warm air stops rising )
Tall clouds - form in unstable air ( the warm air continue to rise )
Note: This is often a function of the ground temp
What are the 4 ways clouds form?
Convection
Orographic
Turbulent
Frontal
How do convection clouds form?
Surface level air is hotter than air.
Air parcel rises - and cools adebatically.
Results in broken sky with patches of cumulus
Height is defined by the stability.
What conditions are required for Towering Cumulus formed via convection?
The surface temp is rising
The Environment Lapse rate is steep.
What conditions are suitable for Convection forming clouds?
( over land and over water )
Over land
* mid-afternoon ( max ground temp )
* Spring, Autumn, Summer ( ground is warmer than air )
* Clouds disapate in the evening
Over Water
* Winter time (water is warmer than air )
* Clouds stay during the night, as water has a lower temp variation than land.
What conditions cause turbulence clouds
High relative humidty
Wind, at least 8kts ( to move the air )
Stable lapse rate
Usually forms stratus clouds.
If the air is unstable, get large cumulus clouds ( no inversion to hold the height )
Can also be caused by air from sub tropical moving to more temperatue lattitudes, due to the difference in the temp, results in wind flows.
What causes Orographic clouds to form?
Causes by terrian
- Rising Terrain, forces the air upwards
- Results in adabetic cooling.
- Stable air = stratus clouds over the top
- Unstable air = cumulus on the lee side
- Usually requires a mountain range ( air can flow around a hill )
What conditions create what type of Orographic clouds?
Lenticular
* Dry air at the base
* Moist air at the top
* This can create standing mountain wave on the lee side
Stratus
* Moist air at the base/top
* Stable at the top
Cumulus
* Moist air base/top
* Unstable at the top
What are frontal clouds?
Caused when either:
* Warm air moves toward cold air ( usually fair weather )
* Cold air moves toward warm air ( unsettled weather)
In both cases the warm air goes up and the cold air goes down.
What are the conditions at a warm front?
- Fine weather under the cloud formation
- Cirrus develop at the upper levels
- Precip up to 200NM ahead of the front
- Move into fine weather
- Slope is constant
*
What are the conditions at a cold front?
More servre weather
Cumulonimbus tend to form
Slope is steeper
Cumulus clouds
Heavy precip.
