Exam Prep

Question 1

How does temperature affect the wavelength and frequency of radiation emitted?

Answer 1

Weins law states zone of peak wavelength emissions is inversely proportional to its absolute temperature.
And so if the increase in temperature decreases wavelength, frequency must increase.

Question 2

How does wavelength determine the type of radiation emitted?

Answer 2

High temperatures emit visible light/gamma rays whilst cooler temperatures emit more electromagnetic radiation (microwaves/IR).
IE) the sun is high temp so emits short wavelength/high freq

Question 3

Name the electromagnetic spectrum in order

Answer 3

Gamma, X-ray, UV, VL, IR, microwave, radio

Question 4

What is the difference between sky radiation and global solar radiation?

Answer 4

Sky radiation: scattered radiation that reaches the earths surface
GSR: sum of sky radiation and direct radiation, aka total solar radiation reaching the earth

Question 5

What form of radiation heats the earth up? Explain how

Answer 5

Solar radiation reaches the surface causing the surface molecules to excite, causing the surface to increase in temperature. They then emit energy as terrestrial radiation which is what warms the atmosphere. Can be described as a hot plate effect. As the surface emits energy it will cool, so needs a constant supply of solar radiation to allow the surface to warm

Question 6

Explain the 2 ways heat is transferred in the atmosphere? (Not inc latent heat)

Answer 6

Conduction: heat is transferred by sensible heat through intermolecular action, mainly occurs near the surface
Convection: heat is transferred by sensible heat through layers of the atmosphere as gases rise

Question 7

What is latent heat? Explain how latent heat affects water going from gas to liquid and its surroundings?

Answer 7

It is the heat transfer as a substance changes state. Gas to liquid requires a release of energy, so the surroundings will warm. However, the temperature of water will remain constant in the state change

Question 8

What are the 3 main factors that influence the amount of solar radiation received by the earth?

Answer 8

Distance between the sun and earth.
Altitude of the sun.
Length of day.

Question 9

Explain how distance between sun and earth affects the amount of solar radiation received?

Answer 9

As the earth orbits the sun in an elliptical way, the distance is always changing. The earth is closest at perihelion (3rd Jan), and further east away at aphelion (3rd/5th July). Inverse square law states the energy received decreases with the square of the distance between the two

Question 10

Explain factors affecting altitude of the sun

Answer 10

Time of day: radiation is received more perpendicularly at noon compared to mornings/evenings.
Latitude: radiation is received more perpendicularly at the equator (at equinox) or at tropics at solstice -(Dec 23rd SH summer solstice, June 23rd SH winter solstice). At lower latitudes same energy is spread over a wider surface area.
Season: the season is largely the factor which determines the other two above due to the earth receiving radiation at various angles

Question 11

Explain how length of day affects amount of solar radiation received by the earth

Answer 11

Equatorial regions receive approx equal amounts of day/night per 24h, but further toward poles receive more day in summer and less in winter. However all parts of the world will receive equal day/night at equinoxes in March/September 22nd.

Question 12

Describe what happens to conduction (terrestrial radiation) and convection once nighttime

Answer 12

Conduction still occurs but convection continues

Question 13

Describe what RVR is.

When is RVR notified to pilots?

Answer 13

Runway visual range is a aid for pilots to know the prevailing visibility along the runway in use, from 5m above the touch down point, measured with sensors at the threshold, midpoint and stop end of runway.
Is only used (METAR/SPECI) when v<1500m. (Ie: R23L/0600= RWY 23L vis 600m)
ATIS when v<600m

Question 14

What do the letters P, M, U, D, N, V mean in an RVR?

Answer 14

P: max distance of sensor detected so may be greater than reported. R05/P1500
M: less than min distance the sensor can detect. R05/M0050
U: trending upwards D: trending downwards N: neutral trend. R05/1200U.
V: varying between R05/0600v1200

Question 15

How does an increase in altitude affects ones ability to see?

Answer 15

As altitude increases the brightness of the sky decreases but glare will increase. There is also significantly less dust/cloud/particles so the eye is unable to focus as well.

Question 16

Describe slant ranges effect on visibility

Answer 16

Flying overhead the station may have clear view as you look perpendicularly to the aerodrome, but as you look through a haze layer at an angle the visibility decreases. The higher your are the greater visibility you will have, not that you can see through more haze, but the distance you can see ahead is greater.
Visibility is often greater on the surface than at when flying below a cloud with virga.

Question 17

Describe the particles involved in Rayleigh and mie scattering

Answer 17

Rayleigh is performed by individual gas molecules 1/10 smaller than the wavelength and will scatter in all directions evenly.
Mie scattering is done by larger aerosols which are larger than the wavelength and will primarily scatter forwards.

Question 18

Describe the formation of radiation fog

Answer 18

Best occurs on cool winter nights in high pressure systems (stable) with a high relative humidity/high DP. As solar radiation ceases, terrestrial radiation as it leaves the surface is not replaced so the surface cools, and through conduction cools a small layer above the surface. If there are light winds less than 5kt, this allows mixing and a deeper layer of cool air through convection. If the air cools to DP then the air will saturate and form fog.

Question 19

Describe the dissipation of radiation fog

Answer 19

As the sun rises it warms the layer of fog, but as the layer of cloud turn to gas it’s requires latent heat so absorbs heat from the surroundings, cooling the atmosphere making the fog initially worse. The fog will evaporate off ground upwards.

Question 20

Name some orographic influences on the formation of radiation fog

Answer 20

Katabatic winds (down) enhances valley fog as they contact the cool valley walls (valley fog).
Mudflats and swamps help form fog as they provide moisture.

Question 21

Can radiation fog form after sunrise?

Answer 21

Yes, if the solar radiation promotes the mixing required then it may form after sunrise

Question 22

Describe the formation of advection fog

Answer 22

Requirements are almost exactly those of radiation fog. The difference is the method of cooling. Moist air is transported over an already cool surface and cools to DP.
A stable air system is ideal but not required for this formation, it just limits the development of cloud into Sc. An inversion is required however to limit the vertical development. Wind 6-15kt

Question 23

Describe the dispersal of advection fog

Answer 23

Either a change in the direction or velocity of wind speed.

Or advection if less moist air

Question 24

Just know these differences between radiation and advection fog

Answer 24

Radiation fog can only form over land whilst advection fog can form over land/water.
R fog requires a cooling surface while a fog requires an already cool surface.
R fog will disperse after sunrise while a fog can last for days if the right conditions persist.
Radiation fog requires a high/col conditions while a fog it is not absolutely necessary.

Question 25

What are the requirements for a thunderstorm?

Answer 25

An unstable atmosphere.
Large amounts of moisture.
Cumulus cloud that can develop.
Trigger action

Question 26

Describe how orographic thunderstorms form and their duration. When are they most common?

Answer 26

They form as moist unstable air is forced over high terrain. Seasons and time of day have no major impact on this type of thunderstorm, although thermally unstable air may be easier met on summer/autumn days. Unlike other thunderstorms which typically are short lived, orographic thunderstorms can last as long as moist unstable air is forced over terrain.

Question 27

Describe the formation of heat type thunderstorms. How does their timing differ from tropical to temperate climates?

Answer 27

Thermal TS require intense heating from below to encourage instability of warm moist air. Best occurs near large water sources to help Cb develop. In temperate climates will occur mainly in summer during the afternoon along coasts. In tropical climates it is a daily occurrence that can last past sunset throughout the year, it just along coasts

Question 28

Describe what can lead to convergence thunderstorms

Answer 28

…convergence.
Heat type TS technically fall into this category.
Low pressure systems or the ICTZ can also create convergence.
Basically any system that causes moist unstable air to converge and rise.

Question 29

Describe how nocturnal equatorial thunderstorms form. Where and when are they most likely?

Answer 29

They form +/-10* of the equator where the oceans are warm (30*c). As the sun sets, the water retains its temperature but the upper atmosphere cools which steepens the ELR (large ELR). At dawn the ELR is greatest and this is when the storms are most likely to occur, dying out by mid morning.

Question 30

How do cold stream thunderstorms form? When do they occur in NZ/AUS? How strong are they?

Answer 30

As cool air passes over a warm patch of water, it absorbs large amounts of water and its lower levels warm. The warming of the lower levels steepens the ELR (greater) allowing instability vertical mixing which can generate Cb.
Can occur in Aussie as polar air moves over in winter/spring or in NZ in summer/autumn.
Are not usually as intense as the others.

Question 31

Describe the formation of frontal thunderstorms. What is their duration? What relevance are squall lines?

Answer 31

Occurs as warm moist air is forced upwards at a frontal boundary. Best occurs with cold fronts but not to say it can’t happen with warm fronts. They are relatively short lived as the front face moves quickly.
Squall lines can be apart of the cold front or self propagating ahead of the cold front. They are marked by a sudden wind change and gusty conditions.

Question 32

Explain the direction of up/down droughts in the different stages of a TS. When are they strongest?

Answer 32

Up: growth
Both: mature
Down: decay
Updraughts are typically stronger, especially from the centre to top of the Cb. Downdrafts are typically stronger from the centre of the cloud to the bottom.

Question 33

What are the dangers with drafts in Cb?

So to conclude, what is the primary/secondary issue with up/down droughts?

Answer 33

Up: small a/c not fitted with O2/icing which is an increased risk at high altitudes. Also rapid onset of -ve g can exceed a/c limitations.
Down: can out do the RoC of a/c which causes crash into terrain
Transition: change in speed causes turbulence and can cause excessive g-forces which exceed the limit of a/c. Will be most common in mature stage.
P: altitude control
S: Turbulence.

Question 34

What significance to gusts have in a Cb? How are they different from up/down droughts?

Answer 34

Gusts are short term localised variations in vertical/horizontal airflow, additional to any up/down droughts.
They dangers are excessive load factors, excessive change in speed (Vne/Va), abrupt control movements to correct.
Most likely to be found in the dividing sections of up/down droughts in mature stage.

Question 35

Discuss the characteristics of a gust front

Answer 35

Cold air is descending our of a mature/decaying Cb, will hit the surface and largely spread out in the direction of travel of the Cb. This air will return back into the Cb as a warmer/slower return flow, creating a “shear zone”.
An a/c descending through this zone will notice changes in wind speed and direction

Question 36

What are the dangers of flying into icing?

Answer 36

Can cause buildup of ice on the airframe, engine intakes or pitot tube intakes. Icing on Ariels and propellors can also pose a large threat.
It will also make the a/c less aerodynamic, add weight, increase the stall speed.

Question 37

What altitude above the FZL is icing the worst?

Is it better to fly through the tops or bottom on Cb icing clouds?

Answer 37

The first 6-8000ft due to supercooled water and droplet size cause clear ice, which is hard to see and remove. Near the tops amount of supercooled water reduces and rime ice, which is easier to remove is more likely.
Tops, assuming the a/c is anti ice equipped, this is better than the turbulence expected below.

Question 38

What are some hazards with lightning?

How are some offset?

Answer 38

Relatively nil. But:
Static comms and Ariels will snap off if struck.
Temporary blinding of crew.
Electronic equipment may suffer some damage
Compass will have large deviation.
By having static wicks to discharge any electric charge built up by lightning, flying through Cb/rain/dust.

Question 39

Where is the worst location for hail in a Cb?

Answer 39

In mid latitudes 8-25000ft, higher in tropics

Question 40

How are tornadoes formed?

Answer 40

When there is an existing rotation below a Cb (wind shear)which is drawn upwards due to convergences

Question 41

What is an air mass?

Answer 41

A large volume of air in the horizontal plane which shares characteristics of temperature, temperature lapse rate and moisture through a vertical column

Question 42

What factors allow an air mass to absorb characteristics?

Answer 42

Large uniform area
Shallow pressure gradients (light winds)
Anticyclonic conditions (sub tropics and polar regions)
Steady ELR
Remain over source region for 5-7 days

Question 43

Describe the moisture, temperature, stability and tropopause height of maritime arctic, polar and tropical air masses

Answer 43

Arctic: moist, cold, stable (upper) unstable (lower), low
Polar: moist, cold, stable, medium
Tropical: very moist, warm, unstable, high

Question 44

Describe the moisture, temperature, stability and tropopause height of continental arctic, polar and tropical air masses.

Answer 44

Arctic: dry, very cold, stable, very low
Polar: dry, cold, stable, low
Tropical: dry, hot, very unstable, very high

Question 45

Name places in Ac, Pc & Pm climates

Answer 45

Ac: arctic, Antartica, northern Canada and Siberia in winter
Pc: northern Canada and Siberia in summer
Pm: high Southern Hemisphere latitudes around oceans

Question 46

What label is given to warm/cold air masses that migrate to new locations?

Answer 46

W warm and K cold.
They take their original temperature…
So Pm air mass moving tropics is PmK, Tc air mass moving poleward is TcW

Question 47

What atmospheric changes occur in cold advection?

Answer 47

Cold air moves to warmer regions. (PmK/PcK)
Lower levels will warm which steepens the ELR creating instability and Cu development. Extent of mixing depends on how deep the warming occurs. Eventually the upper troposphere will warm up.
If over oceans, Cu/Cb development likely. If over land, still unstable but less cloud development.

Question 48

What affects does cold advection have on Australasia?

Answer 48

The lower levels will warm steepening the ELR, and gaining moisture initially making few layer Cu/Sc. The further north travelled the more instability and moisture gained due warmer oceans. This increases the likelihood of Cb/Cu development south of Aus.
Coastal Aus will be cold, have good vis (except in showers) and possible HA/TS if very unstable. Inland instability will still occur but with reduced/higher level cloud. Will modify into Tc over time.
NZ will have bad wx west coast but sheltered wx east coast.

Question 49

What atmospheric changes occur in warm advection?

Answer 49

Lower layers will cool which shallows the ELR and increases stability. Will be labelled TcW or TmW.
If TmW advects south it’s lower levels will saturate easily so low level fog (slow moving) or low level stratus (faster) with drizzle and bad vis. If this air moves over hilly terrain cloud will develop with rain.

Question 50

What effects does warm advection have on Australasia?

Answer 50

As warm moist air moves south it’s lower levels will cool and condense to form low level cloud/stratus and fog. The subsidence due stability reduces vertical mixing so upper layers will cool slower so may result in inversions.
As this air reaches NZ, it will be forced aloft due terrain which will create cloud, rain/drizzle and reduced vis. Will mainly affect Northland, BoP, Auckland, Malbrough Sounds & Nelson but May differ due moisture content, direction of flow and time of year.

Question 51

Is airmass modification thermal or dynamic modification? Explain

Answer 51

It is the horizontal transport of air over different temperature surfaces. Air in lower levels is advected/radiated so thermal process.
The resulting ELR (especially in cold advection) creates vertical motion which is the dynamic modification (adiabatic) which is the main process for AMM in the middle and upper atmosphere.

Question 52

What is specifically meant by a greater pressure lapse rate? Does warm or cold air have a greater PLR?

Answer 52

Greater PLR means 1hPa change in a smaller vertical distance, ie) 30ft/hPa>40ft/hPA.
So cool air has a greater PLR than warmer

Question 53

What factors determine the strength of a thermal wind?

Answer 53

The difference in temperature between two columns, so the resulting pressure variation. Larger difference larger wind.
Distance between the two columns. Larger difference smaller wind.
Difference in sea level pressure of each column.

Side note, each layer will have its own strength of thermal wind due to the difference in pressure due temperature differences.

Question 54

Describe how a thermal wind blows and the law used to determine this

Answer 54

Takes into account Buys Ballot law… which accounts for the coriolis force.
In the SH, when the thermal wind blows onto ones back the cold core centre will be to your right. (NH is to left).
Thermal winds blow parallel to isotherms/perpendicular to thermal axis.

Question 55

How to calculate the strength and direction of a thermal wind?

Answer 55

Strength= mean temp gradient (c/100Nm) x height in 1000’ft
Direction upper wind= surface wind + thermal wind
So: take direction of thermal wind by +/- 90 to thermal axis
Then use vectors to find a2= b2 + c2 -2bc sinA to find direction.

Question 56

What effect does a thermal wind in the SH have on wind direction? For the SH

Answer 56

For mid latitudes:
Will make wind at upper levels more westerly.
Will enhance westerly, reduce easterly & turn westerly, will make northerly back and southerly veer
For tropics:
As tropopause is cooler as higher moving away from equator means an increase in temp so thermal wind becomes easterly.

Question 57

What is SAM? How do we identify the phase?

Answer 57

Southern annular mode is a climate variability encircling the South Pole extending the NZ latitudes. It brings variation in the location & strength of the westerly winds of the mid latitudes as they shift north (negative SAM) or southern (positive SAM).
+ will bring light winds and high pressure system over NZ
- will bring stronger winds and low pressure systems over NZ

Question 58

What are the effects of SAM on NZ?

How long does one SAM event last?

Answer 58

A + SAM:
-shift the westerlies southward
-more settled weather over NZ
-less rain and higher temperatures (less rain WC SI, little less EC NI)
-while bad weather lies south (fewer frontal systems)
Whereas a - SAM
-westerlies northward and brings more stormy unsettled weather to NZ -more settled weather lies southern oceans.
-bad weather will hit west coasts more due to topography
-colder
May last several weeks once established
Will affect South Island more than the north

Question 59

What relationship is El Niño with SAM?

What has been the general trend of SAM?

Answer 59

El Niño typically will correspond with a -ve SAM

More positive events

Question 60

Describe the difference between the thermal equator (equatorial trough) and the ICTZ

Answer 60

The equatorial trough is a permanent low pressure belt that occurs due to intense heating (convection), that follows the thermal equator, creating convergence and instability.
The ICTZ is a synoptic feature within the equatorial trough that exists where the trade winds convergence that will change its location, cloud cover and intensity regularly. Areas under the ICTZ are the doldrums.

Question 61

Where is the max cloudiness or ICTZ likely to lie in relation to the equatorial trough?

Answer 61

2* equatorward

Question 62

Describe the seasonal location of the equatorial trough

Answer 62

In the NH may-oct, ET will lie entirely in the NH. Due to vastly different terrain it is not uniform latitudinally (particularly India/China). Over oceans it is fairly constant.
In SH oct-apr, ET is relatively uniform latitudinally, except for kinks across Australia and South Africa. The ET will lie in the SH, except for over the pacific and Atlantic oceans where it remains in the NH, due to stronger trade winds and oceanic temperature influences.

Question 63

Describe the seasonal location of the ICTZ

Answer 63

F

Question 64

Describe the cause and location of the South Pacific convergence zone. When is it most active? What can strengthen the SPCZ?

Answer 64

Is caused by a high pressure in the east pacific causing SE turning NE winds the the west pacific converging with SE winds from a high pressure in the Tasman region.
This causes convergence in a region near Papa New Guinea/French Polynesia which generates intense cloudiness.
Most active in summer and CF moving NE.

Question 65

Simply, how do they trade winds blow? What direction do the trade winds flow? What is the vertical limits?

Answer 65

The air from high pressure belts at 30* N/S travel toward the low pressure at the equator and is deflected eastward by the coriolis force in both hemispheres at approximately 10-20kt. Is no higher than 8000ft.
Specifically SE SH, NE NH.

Question 66

How do the trade winds change seasonally?

How does the shape of the ICTZ change seasonally?

Answer 66

Stronger in winter than summer.
Summer SH: Uniform over pacific then dips south over Brazil, back equatorward then dips over Africa then brushed over N Australia, back into NH over pacific.
Summer NH: Fairly uniform expect will rise over India/China.

Question 67

Where does the ICTZ never enter the Southern Hemisphere?

Can the trade winds cross the equator?

Answer 67

In the mid Pacific Ocean.
Yes they can, they chase the equatorial trough.
When the ICTZ is in the NH (summer), the SE from SH turn SW.
When ICTZ is in SH (summer), the NE from the NH become NW.
(Easterlies veer westerlies)
Remembering the ICTZ does not cross the equator over the Pacific Ocean.

Question 68

What is the effect on ICTZ weather due to islands north of Australia?

Answer 68

During summer, the temperature of the island are slightly higher than the oceans which creates a sea breeze effect. This reduces the pressure above the island which increases instability, creates rainfall and cloudiness, especially on SE coasts as the TW blow on.
During winter the opposite occurs and the air is more stable and drier.
Cloudiness May still occur on SE coasts but not as much.

Question 69

Describe mesoscale convective areas

Answer 69

Areas 100-1000km^2 of grouped Cu/Cb, characterised by instability through deep layers, often apart of the equatorial trough. Don’t generally last more than 1-2 days but can persist longer if ICTZ is active.

Question 70

What is a wave disturbance?

Where do they originate?

Answer 70

A low pressure belt that moves east in the tropical regions, but not necessarily at the same speed as the trade winds.
They are more common in the NH, and are typically 2-4* poleward of the equatorial trough.

Question 71

Describe what weather will be noticed either side of the trough if the wave disturbance moves slower than the trade winds or faster than the trade winds

Answer 71

If the trough moves e-w faster than the trade winds, convergence will occur to the west/ahead (bad wx) and divergence will occur on the east/behind (good wx).
If the trough moves slower than the trade winds, convergence occurs to the east (bad wx) and divergence will occur to the west (good wx).

Question 72

Describe x4 characteristics of a wave disturbance

Answer 72

Last 10 days
3000km in length
Slope eastward with altitude
6* longitude per day

Question 73

What direction does the wind blow above the trade winds?

Answer 73

Westerlies

Question 74

Describe the weather around the trade winds/ICTZ due to subsidence

Answer 74

Under the high pressure belt is subsidence so good weather. As the air moves equatorward, so this meets warmer air and subsidence is decreased, possibly even creating subsidence inversion 6-8000ft AMSL (rising closer to equatorial trough).
Below inversion is fair vis and weather with cumulus building ups 2-3000ft AMSL, and above inversion is great vis and clear stable skies.

Question 75

What is a blocking anticyclone? How do they form?

Answer 75

In low zonal index situations (up/down movement) there are places where high pressure systems are locked in place and can prevent the eastward movement of weather systems.
They form as upper level westerlies split into two. Northward bound air turns right and therefore is trough and southbound air turns left so ridge. The high pressure is intense and extends to the tropopause.

Question 76

What will a blocking high to the east of NZ cause weather wise?

Answer 76

West EC and dry WC with NE winds

Opposite but with SW winds

Question 77

Dimensions of active ICTZ?

Answer 77

500-600km wide

50-60000ft high