Met 2 22/2

Front 1

For an anticyclone, does air converge or diverge at the surface?

Back 1

Diverges at the surface, converges at upper levels

Front 2

In terms of general atmospheric circulation, where does NZ lie?

Back 2

Mid latitude cell, below the sub-tropical high pressure zone, and above the polar low-pressure zone

Front 3

For jets, what can you expect of the cloud activity in the vicinity?

Back 3

STJ: cloud band on the equatorial side.

PFJ: cloud band polar side. Both are cirrus

Front 4

What’s a monsoon?

Back 4

A seasonal cross-equatorial wind flow, enhanced by continental sea breeze effects

Front 5

What/where is the ITCZ

Back 5

The inter-tropical convergence zone is the area close to the equator where the trade winds meet

Front 6

Characteristics of the maritime tropical air mass at the surface

Back 6

Warm, moist, and stable

Front 7

How is hail made?

Back 7

SCWD in CBS collide with ice particles, and the particle grows until it’s too heavy

Front 8

What’s required to make Lee waves in the southern alps?

Back 8

Wind speed above 20kts at ridge tops, increasing wind speed with height, wind direction perpendicular to the ridge line, wind direction remaining constant with height, and a stable layer around ridge top level.

Front 9

Why would SCWD freeze slowly on an aircraft?

Back 9

Latent heat slows the freezing process down, and more is released at lower altitudes. Also the water droplets are larger. Freezing takes longer, so air is dispelled, and the ice glazes.

Front 10

Jetstream definition

Back 10

Any sustained wind of 60kts or more

Front 11

Where does an orographic trough form?

Back 11

Leeward side of the mountain

Front 12

VA in regards to satellite imagery and aircraft radar?

Back 12

Satellites can see VA, but aircraft weather radar can’t

Front 13

If a cold front hit Ohakea from the West, what would you expect?

Back 13

A pressure decrease as the front passes, followed by an increase in pressure.

Front 14

What conditions would produce blowing dust?

Back 14

An extended dry period, marked instability, strong surface winds, and enhancement by cold fronts.

Front 15

Describe the lifetime of a single cell thunderstorm

Back 15

30 minutes for each stage, 1.5 hours approximate total

Front 16

Why isn’t airframe icing a problem below -40°?

Back 16

All cloud droplets are already frozen at that height

Front 17

Describe the first stage of a thunderstorm life cycle

Back 17

Cumulus stage: only updraught present. Massive latent heat released due to cloud formation. Light rain possible, as is airframe icing aloft due to SCWD in the updraught.

Front 18

Describe the second stage of a thunderstorm life cycle

Back 18

Mature stage: most CB hazards exist, updraft and downdraft are present, and the anvil begins to form.

Front 19

Describe the third stage of a thunderstorm life cycle

Back 19

Dissipating/anvil stage: updraught ceases, as do hazards. Bottom 2/3 of the cell evaporate, leaving the cirrus anvil behind

Front 20

Mountain range Lee waves and rotors diagram

Back 20

Rain on the windward side of mountains, a friction layer (the line that depicts the base level Lee wave), a stable layer (to provide the restoring force), rotor zones, counter rotating zones above, and lenticular clouds in the moist layers.

Front 21

How does a cold anticyclone form at the surface?

Back 21

They only form over very cold surfaces. The air in contact with the surface is cooled by conduction, this air condenses. The layer of air descends, increasing pressure. An anticyclone forms.

Front 22

What causes Earth’s vorticity?

Back 22

Earths rotation causes a linear shear force that increases with latitude.

Front 23

What is an airmass?

Back 23

A large mass of air whose physical characteristics of temperature and humidity are approximately the same, level for level, over large horizontal distances.

Front 24

What clouds and precipitation accompany maritime polar air moving to NZ?

Back 24

Cold air is warmed from below, creating instability, and increased convection, resulting in cumulus clouds and showery conditions.

Front 25

How do changes in absolute vorticity lead to convergence and divergence?

Back 25

Earth’s vorticity acts in a cyclonic direction. Therefore absolute vorticity will be greatest in a cyclone, and lowest in an anti-cyclone. To change speed between these troughs and ridges we have convergence and divergence.

Front 26

What are the pros and cons of infrared and visible satellite imagery

Back 26

Infrared provides imagery at night, and can reveal temperatures (and therefore height). Regular satellite imagery cannot tell altitude.

Front 27

What are the pros and cons of infrared and visible satellite imagery

Back 27

Infrared provides imagery at night, and can reveal temperatures (and therefore height). Regular satellite imagery cannot tell altitude.

Front 28

What’s the equation for thermal wind?

Back 28

Low level wind + thermal wind = upper level wind

Front 29

What is the thermal wind?

Back 29

Otherwise known as a vertical geostrophic windshear, the thermal wind is the difference between winds at different vertical levels - represented as a vector.

Front 30

What are the characteristics of an STJ

Back 30

1. Driven by the conservation of angular momentum

2. Mostly continuous around the globe.

3. Usually located above the sub-tropical belt of high pressure (25-35degS)

4. Very zonal

5. Found around 40,000ft

6. Typical NZ speed of 80kts in summer to 120kts in Winter, gusting 200kts.

Front 31

What drives polar front jets?

Back 31

Large temperature differences found above frontal zones (the thermal wind).

Front 32

What are the three factors that influence our climate

Back 32

Oceanic environment, higher relief, and our location within a westerly flow - bringing travelling highs, lows, and variable weather.

Front 33

What is the thermal wind?

Back 33

Otherwise known as a vertical geostrophic windshear, the thermal wind is the difference between winds at different vertical levels - represented as a vector.

Front 34

What temperatures does rime ice form in?

Back 34

-20 to -40 degrees

Front 35

What’s required for rotor streaming?

Back 35

Wind perpendicular to ridge line, and strong winds at ridge top height but decreasing above.

Front 36

List common problems with weather radar

Back 36

Bug swarms show, sunrise/sunset interferes, some frequencies interfere, sea clutter shows without algorithms, heavy precipitation can cause readback issues (attenuation), and waves trapped beneath inversions can create ground echoes (ducting).

Front 37

What are the characteristics of an STJ

Back 37

1. Driven by the conservation of angular momentum

2. Mostly continuous around the globe.

3. Usually located above the sub-tropical belt of high pressure (25-35degS)

4. Very zonal

5. Found around 40,000ft

6. Typical NZ speed of 80kts in summer to 120kts in Winter, gusting 200kts.

Front 38

What drives polar front jets?

Back 38

Large temperature differences found above frontal zones (the thermal wind).

Front 39

What are the three factors that influence our climate

Back 39

Oceanic environment, higher relief, and our location within a westerly flow - bringing travelling highs, lows, and variable weather.

Front 40

What shows a high westerly index?

Back 40

Isobars indicating high westerly winds

Front 41

What are the requirements for thunderstorm formation?

Back 41

An adequate supply of water vapour at low levels, conditional instability, and a trigger mechanism such as convection, orography, or frontal lifting.

Front 42

What are the advantages of geo stationary satellites compared to polar orbit ones?

Back 42

Polar satellites sit around 850km above the surface, have low maintenance costs, see the poles regularly, and get higher res images for a lower cost. Geostat satellites are more expensive, can’t photograph as high a resolution, and don’t see the poles clearly, but can maintain 24/7 watches on one area. They sit at 36,000km.

Front 43

Why does visibility reduce close to the surface with blowing snow?

Back 43

A stable layer means that blowing snow stays at low level near the ground.

Front 44

What causes whiteout?

Back 44

Whiteout is an optical effect caused by diffuse illumination. Shadows disappear, and contrast goes with it.

Front 45

What temperatures does glaze icing occur in?

Back 45

most severe from -5 to -8 degrees

Front 46

How high is the tropopause above NZ?

Back 46

Approximately 12km (40,000ft)

Front 47

What are flight hazards posed by CBS?

Back 47

Turbulence, electrical activity, icing, hail, impaired visibility, microbursts/gust fronts, and tornadoes.

Front 48

What dictates the flow of wind over the southern alps?

Back 48

Stability of the air, wind strength, angle of the wind flow to the ranges, the nature of the topography, and the vertical profile of the wind speed and direction.

Front 49

What are the dangers of flying in Lee waves?

Back 49

Severe turbulence in rotor zones, strong down drafts, strong local winds (with potential hydraulic jumps), and possible severe airframe icing.

Front 50

How are warm anticyclones formed?

Back 50

Dry air is forced downwards at the DALR, then stopped by weak convection from the surface.

Front 51

How are warm anticyclones formed?

Back 51

Dry air is forced downwards at the DALR, then stopped by weak convection from the surface.

Front 52

What are the characteristics of a warm anticyclone?

Back 52

Clear in the middle, good visibility with showers in the east, and anticyclonic gloom in the west (with stratocumulus cloud), caused by the inversion.

Front 53

What are the hazards of anticyclones?

Back 53

Low vis and low cloud to the west, high winds and turbulence on the fringes of the high, fog forming in the center, and summer thunderstorms

Front 54

What are the dominant airmass types for NZ?

Back 54

mT (maritime warm) and mP (maritime cool)

Front 55

What are exceptions to the main depression formation?

Back 55

Lee depressions, heat lows, and tropical cyclones