Met Syllabus

Question 1

Define the terms:

(a) troposphere
(b) tropopause
(c) stratosphere

mesosphere
thermosphere
exosphere

Answer 1

Troposphere

Lowest layer of atmosphere
Surface to (average) 36,090ft/11km
Temp decreases with alt
Most aerosols/water vapor = most wx
75% of total atmosphere mass

Tropopause

The isothermal transition layer between the tropo/stratosphere.
The lower limit of the generally stable layer which caps the troposphere.
Location of atmospheric jet streams.

Stratosphere

Temp increases with alt (11-50km) from -56.5 to -2 as a result of the absorption of UV by large concentrations of ozone (10 parts p/million)
21% of total atmosphere mass.

Mesosphere

Temp decreases with alt (50-90km Kaman line)
Very low pressure (1-<0.01 hPa)

Thermosphere

Temp increases with alt up to 500km due to direct radiation from the sun

Exosphere

Temp decreases with alt
Upper limit indeterminate

Question 2

Nacreous and Noticulent cloud (only 2 types of stratospheric cloud)

Answer 2

Nacreous

Form during winter
15-25km high
Ice crystals / SCWD
Contribute to ozone depletion due to nitric acid content

Noticulent

Observed in summer
75-85km high
High lat (50-65 N/S)
Ice and space debris

BOTH visible only at night due to illumination by the sun below the horizon. They can form during the day but are unable to be seen due to their altitude and the volume of visible light.

Question 3

Explain how the following changes within the tropospheric column affect the height of the tropopause:

(a) surface pressure
(b) temperature

Answer 3

Pressure

If surface convergence exceeds upper level divergence (low pressure), the column of air will lower.
If upper level convergence exceeds surface divergence (high pressure), the column of air will rise.

Temperature

Heating will result in the expansion of column in the vertical, and vice versa if cooling. This will occur without a change in surface pressure.

Usually temp and pressure changes occur silmultaneously in the atmosphere but with one more dominant than the other.

Question 4

State the average tropopause heights and tropopause temperatures at:

(a) the equator
(b) the poles
(c) in mid-latitudes

Answer 4

Equator - 56,000ft -75c
Mid lats - 36,000ft -56
Poles - 26,000ft -48

Question 5

Explain:

(a) the sources of aerosols within the atmosphere
(b) the effects of aerosols within the atmosphere
(c) the importance of aerosols within the atmosphere

Answer 5

The source of all aerosols in the atmosphere is the surface of the earth.

They can be primary (90%) or secondary (10%), primary sources can be natural fires, volcanic ash, sea salt, pollen, and human activity. Secondary form when primary aerosols mix and coagulate to form new substances. Sea salt and dust are two of the most abundant aerosols.

Aerosols come in 2 forms, condensation nuclei, and freezing nuclei. Condensation nuclei are numerous at low-mid levels and they are the building blocks for almost all of the clouds in the atmosphere. Freezing nuclei are not common at temperatures just below freezing but at higher altitudes, they exist in great numbers. Above -40c only freezing nuclei exist and all cloud - cirriform, is made up of ice crystals. Aerosols may reduce visibility, especially when trapped beneath an inversion, and are the building blocks of clouds and thus precipitation, meaning any storms result from their existence.

Without them we would have no cloud, fog, or precipitation, the visibility would be excellent and we would have no airframe icing.

Question 6

Describe the effect of increasing height and/or latitude on water vapour and aerosol content
within the atmosphere.

Answer 6

Both WV and aerosols originate from the surface of the earth and hence the highest concentrations of both are generally close to the earth’s surface.

This holds true over most of the globe, except antarctica and to a lesser extent the artic during the N hemisphere winter where WV and aerosols can be scarce. This can result in a rare super saturated environment where there is 400% RH and no cloud.

WV content
Higher at lower latitudes (1-5%) vs. <10ppm at poles.
In Troposphere 50% found below 1.5km, <1% above 12km
Stratospheric concentrations 2-3pmm increasing to 6-8ppm with
altitude

The tropopause acts well as a ‘lid’ meaning that the stratosphere is generally devoid of aerosols and WV.

Question 7

Explain the effects on temperature within the atmosphere due to:

(a) water vapour
(b) carbon dioxide
(c) ozone

Answer 7

WV - latent heat released/taken during the phase changes

C02 - 418.82ppm of atmospheric mass
Absorbs outgoing TR and gradually releases it back into the environment

O3 - 10 parts per million at 20-30km
0.3 parts per million everywhere else
absorbs 97-99% of the medium wave length UV radiation from the sun, cause for most of the increase of temperature in the stratosphere.

Question 8

Describe the following:

(a) conduction
(b) convection
(c) advection

Answer 8

Conduction

The transfer of heat through touching.

Convection

When a parcel of air is heated by conduction, it may become buoyant and rise.

Advection

The horizontal transfer of heat or matter by wind. Conduction results in the parcel of air being warm or cool, that parcel is then advected to another location by wind.

Question 9

Define ‘latent heat.’

Answer 9

It is the heat taken or given back to the environment when a substance changes state without changing temperature - a diabatic phase change.

When latent heat is given back into the environment that is called an exothermic reaction (freezing, condensation, deposition).

When latent heat is taken from the environment that is called an endothermic reaction (melting, evaporation, sublimation)

Question 10

Describe the condensation process.

Answer 10

Condensation is the process of WV returning to liquid state. It requires the air to be cooled to dew point and thus saturated w.r.t WV.

Question 11

Describe the freezing and melting processes with reference to latent heat.

Question 12

Describe the diurnal variation of relative humidity and dew point.

Answer 12

As the sun rises and the air warms:

RH will fall, this is because warm air can hold more WV than cold air and thus the ratio of the amount of WV the parcel of air can hold and the amount it is holding is less.

Dew point temperature will remain the same, this is because dew point is directly related to the amount of WV in the air. Therefore if the DP changes we can be sure that there has also been a change in WV content in the air.

Question 13

Describe the effects of moisture content on the density of the air.

Answer 13

Moisture decreases the density of the air. H20 molecules have a lower atomic mass than 02 and N2.

Question 14

Define
(a) speed
(b) directional
(c) mass convergence
and divergence
(d)confluence

Answer 14

speed
div = air leaves region faster than it enters
con = air enters region faster than it leaves

directional
div = air moves away from a point
con = air moves toward a point

mass div/con = where speed and directional occurs at the same time

confluence = where opposing patterns of speed/direction occur at the same time eg speed con + direction div

Question 15

With respect to the tropopause:

(a) describe the idealised global tropopause detailing approximate altitudes and the position of jet-streams 1
(b) explain why the height of the tropopause varies with latitude and season.

Answer 15

Sub Tropical

40,000ft
Above traveling anticyclones that form around 30S and 30N.

Polar Frontal

30,000ft
Around 60S

Based on temperature alone, a warm column of air at the equator will occupy a larger vertical distance than a cold column of air at the poles.

Question 16

Explain why the stratosphere is generally devoid of cloud and turbulence.

Answer 16

Cloud - lack of WV and aerosols at that altitude
Turbulence - result of inversion layer that is the stratosphere

Question 17

Explain what is meant by the ‘partial pressure’ of a gas.

Question 18

Explain the effects of temperature changes within the troposphere on the pressure lapse rates.

Answer 18

If the column of air is colder, pressure lapse rate will be steep. If the column is warm, the lapse rate will be shallower.

Question 19

Define ‘pressure gradient’

Answer 19

The change of horizontal pressure per unit distance.

Question 20

Describe ‘diurnal’ pressure variations.

Answer 20

There is a natural cycle in daily pressure called the solar tide. It results in 2 pressure minima at 4am/4pm and 2 pressure maxima at 10am/10pm.

Question 21

State the latitudes where diurnal pressure variation is most significant

Answer 21

Most significant in the tropical regions, 23deg26’ N/S of the equator.

Question 22

Explain the effects of changes in the following elements on air density

(a) pressure
(b) temperature
(c) altitude
(d) moisture content of the air

Answer 22

Decrease pressure = decrease density
Decrease temperature = increase density
Decrease altitude = increase density
Decrease moisture = increase density

Question 23

Describe anticyclones with reference to:

(a) their formation processes;
(b) pressure patterns and wind flow
(c) subsidence and subsidence inversions
(d) typical associated weather conditions.

Question 24

Describe the development of ‘cold’ highs.

Answer 24

Cold highs develop when an airmass sits over a surface for an extended period of time - typically it will be a snow-covered continental surface.

These highs develop from the ground up, the air in contact with the surface is cooled through conduction and light wings generate low-level mixing which cools the air to about 5,000ft. This cold air is more dense than the air surrounding it and as it contracts the air surrounding piles in on top of it. The additional air in the vertical column increases surface pressure forming a cold AC.

This type of AC has a strong inversion at or below 3,000ft.

Question 25

Discuss the hazards associated with anticyclones.

Question 26

State the meteorological units of pressure used in:

(a) Australia
(b) USA

Answer 26

AUS/NZ - hPa
USA - inches of mercury / millibars

Question 27

Demonstrate the effect of flying at a constant indicated altitude from a cold region to a warm region, during
which the surface pressure does not change.

Answer 27

True altitude will increase as the vertical column occupies a greater vertical distance

Question 28

Describe the concepts of convergence and divergence.

Answer 28

Convergence - more inflow that is entering a volume in a horizontal plane than is exiting it

Divergence - more outflow that is exiting a volume than is entering it in a horizontal plane

These 2 processes lead to the development of vertical motions in the atmosphere responsible for:

Cloud formation/decay
Surface depression or AC formation/decay
Enhancement of airframe icing
Some turbulence

Question 29

Explain the vertical motions generated by convergence and divergence near the earth’s surface and immediately beneath the tropopause.

Answer 29

Convergence just below the tropopause leads to a downward motion
Divergence just beneath the tropopause leads to an upwards motion

Vice Versa for the surface.

Question 30

With respect to depressions of the Southern Hemisphere outside the tropics, describe the development and associated cloud of the:

(a) mid to high-latitude depression, where upper-level divergence dominates the formation process

Question 31

Describe the temperature reference points of the centigrade scale used in New Zealand aviation.

Answer 31

0 freezing, 100 boiling but only if pressure 1013.25 hPa

Question 32

Explain the factors that influence the amount of solar radiation received at the earth’s surface.

Answer 32

Only 51% of the solar radiation that reaches the atmosphere ends up heating the land or sea. The rest is either reflected or absorbed.

49% reflected by atmosphere (6%), clouds (20%), earth surface (4%) or;

Absorbed by the atmosphere (16%), clouds (3%)

Cloud cover

Some locations are prone to cloudy skies, limiting the available solar radiation reaching the surface of the earth and therefore decreasing the temperature.

Lattitude

As latitude increases the sun’s inclination from the vertical also increases and therefore any energy from the sun is distributed over a larger surface area at the earth’s surface.

Mountainous Terrain

Often mid-afternoon the sun will heat the western faces of ranges to a greater extent per unit area than the east facing side of the range.

Seasons + Time of day

Seasons change the elevation of the sun in the sky and subsequently, the amount of radiation reaching the surface. When the sun is higher, the radiation will be at a vertical angle and concentrated in one area. The length of the day also contributes, typically the longer the day, more insolation. As lattitude increases this is more pronounced.

Albedo

Heat that is reflected by the surface of the earth into the atmosphere, lighter colours, higher albedo, and cooler surfaces.

Question 33

Explain the warming or cooling of the atmosphere with reference to solar and terrestrial radiation.

Answer 33

Global energy budget

The balance between outgoing long wave TR from the earth (15c) and incoming short wave SR from the sun (average 6,000c, during a solar flare up to 350,000c) in a 24 hour period.

Globally, the ingoing and outgoing energy balances however there are marked differences with latitude. At high lattitudes there is an energy deficit, with an energy excess at low latitudes. These are responsible for global patterns of temperature, pressure, wind, and latitudinal climate differences.

Question 34

Total solar irradiance

Answer 34

TSI: average amount of solar insolation at the top of the atmosphere

11 year cycles result in varying energy output of the sun due to sun spot activity.

Changes in the earths orbital path and position relative to the sun.

TSI Average value = 340 Wm2
TSI Max value = 1367 Wm2

HIgher TSI values, higher global temperatures

Question 35

Milankovitch Cycle

Answer 35

Reflects changes in the earth’s orbital path and position relative to the sun.

Eccentricity

The earth elliptical orbital path around the sun is due to the gravitational forces of other planets in the solar system, Jupiter and saturn especially act to pull the earth away from the sun. This elliptical pattern results in the variation of the distance of the earth from the sun, being furthest at the aphelion and closest at the perihelion. Distance dictates the amount of energy received via Inverse square law, as distance increases the amount of energy received decreases at the distance travelled to the power of 2.

Obliquity

The angle or tilt of the earths rotational axis (22.1 - 24.5 degrees perpendicular to the earths orbital plane) The greater the axial tilt, the more extreme the seasons, without any tilt there would be no seasons at all. At the equator the sun is near the vertical and solar insolation is high whereas at high lattitudes the sun strikes the earth more obliquely and the insolation is spread over a greater area.

Precession

The wobble or rotational path of the earth around its axis of rotation. It is due to the competing gravitational affects of the sun and moon as well as large gas planets Jupiter and Saturn. The cycle lasts around 25,000 years and can alter the strength and duration of the seasons in each hemisphere over long periods of time.

Question 36

Describe the following units of temperature:

(a) Celsius
(b) Fahrenheit
(c) absolute (Kelvin).

Answer 36

Celsius + Fahrenheit:

Both measure temperature with reference to freezing and boiling points, it is possible to go above and below FZ and boiling points.

Kelvin:

Begins at absolute zero (-273.15 in celsius), below which it is not possible to go. At this temperature molecular activity ceases and an object no longer produces kinetic energy or emits radiation.

Question 37

Convert between Celsius, Fahrenheit, and absolute temperatures.

Answer 37

C - F = (C x 9/5) + 32
F - C = (F - 32) x 5/9

K - C = K - 273.15

Question 38

Explain what is meant by the terms ‘solar radiation’ and ‘terrestrial radiation.’

Answer 38

SR - radiation emitted by the sun, sun surface hot (6,000K or up to 350,000K during a solar flare) therefore it radiates short wavelengths. energy = 64 million Wm2

TR - radiation emitted by the earth. energy = 390 Wm2

Question 39

State the wavelength of ‘solar radiation’ and ‘terrestrial radiation.’

Answer 39

Solar radiation

UV - <0.4 µm
VIS - 0.4-0.8 µm
INF - 0.8 µm - 1mm

TR (Near INF and INF)

3-100 µm

Question 40

Describe the effect of the following on the amount of solar radiation received at the surface of the earth:

(a) sun angle
(b) length of day
(c) season.

Question 41

Define the terms:

(a) ‘solstice’
(b) ‘equinox.’

Answer 41

Solstice - day where sun is at its most southerly or northerly position from the equator, it stops moving away from the equator and begins to move back toward the equator. Day of year with either most or least sunlight hours.

Equinox - day where both day and night are equal length (12 hours) in both hemispheres at the same time.

Question 42

State the significance of:
(a) ‘solstice’
(b) ‘equinox.’

Answer 42

Solstice - 2 a year, summer solstice for southern hemisphere 21st - 22nd December and winter solstice 20th or 21st June. Day when sun is at its highest declination at the N/S poles. Date when sun is furthest from the equator. Sun directly over tropics (23 deg N/S)

Equinox - 2 a year when sun is directly over the equator. Aprx 20th March and 23rd September.

Question 43

Explain how atmospheric stability is determined.

Question 44

Given plotted graphs of temperature (ELR) versus height, identify and describe:

(a) super-adiabatic temperature lapse-rates (steep ELRs)
(b) inversions and isothermal layers (shallow ELRs).

Question 45

Calculate atmospheric stability by lifting parcels of air given assumed ELR’s, dew point temperatures and
mountain heights.

Question 46

Describe the typical diurnal variation of stability.

Question 47

Describe the relationship between stability of air and cloud type.

Answer 47

Warm subtropic air moving over NZ will be cooling, therefore:

Stable air and stratiform type cloud
(Cs, As, Ns, Sc, St)

Cold sub-antarctic air moving over NZ will be warming, therefore:

Unstable air and cumuliform form type cloud
(Cc, Ac, Cb, Tcu, Cu)

Question 48

List the vertical extents of the three main cloud layers in:

(a) mid-latitudes;
(b) tropical latitudes.

Answer 48

Mid lat

Low - surface - 6,500ft
Middle - 6,500-20,000ft
High - >20,000ft

Tropics

Low - surface - 6,500ft
Mid - 6,500-25,000ft
High - >25,000ft

Question 49

State the difference between the Lifting Condensation Level (LCL) and the Convective Condensation Level
(CCL).

Answer 49

LCL - height at which all non-convective cloud will form (frontal surfaces, convergence, sloping ground, turbulence). Lifted parcel of air cools at DALR until the temp = DP (saturated), cloud forms. Air does not have to be unstable as it is forcibly lifted.

CCL - convection occurs, surface heating produces thermals. Strong surface heating is required to generate thermals sufficient to produce buoyancy. Surface temp must match or > DALR, therefore air must cool further than the LCL to reach DP and saturate (CCL higher than LCL). As these thermals rise they entrain drier air from their surroundings, decreasing the WV content, increasing the cloud base further.

Question 50

Demonstrate the use of simple formulae to calculate the LCL and CCL.

Answer 50

CCL - (ST-DP) x 400
LCL - (ST-DP) x 400 x 0.85

Question 51

Describe the 10 main cloud types as defined by the WMO.

Answer 51

High level

Cirrus - streaky hair liked cloud composed of ice crystals
Cirrostratus - Translucent layer of ice crystal clouds, produces solar/lunar halo
Cirrocumulus - Thin patch or sheet cloud composed of ice crystals in the form of small grain or ripple elements

Mid level

Altostratus - Layer cloud through which the sun is barely visible
Altocumulus - Billowy cloud comes in several forms
Nimbostratus - Dark thick layer cloud

Low level

Cumulonimbus - heaped cloud with large vertical extent, upper portion usually fiborous/anvil shaped
Stratocumulus - Billowy/rolled layer cloud
Stratus - Layer cloud with uniform base
Cumulus - Heap cloud developing vertically, cauliflower tops but smaller than Cb.

Question 52

Describe typical conditions for each of the 10 main cloud types with respect to:

(a) turbulence
(b) icing
(c) precipitation.

Answer 52

ALL cirrus - icing rare although slight rime icing possible

Ci - little turb unless associated with a jetstream. Nil precip

Cs - usually light turb, possible virga otherwise nil precip.

Cc - turbulence indicated by composition (instability at high levels), nil precip.

As - if thin, light turb, -RA/virga, light rime ice possible
if thick, light turb possible mod/sev in fronts, light-mod rime ice, -RA/RA

Ac - light/mod turb, possible light rime icing and virga

Ns - light turb possibly mod/sev with front, mod rime ice possible glaze at lower levels in cloud, mod/heavy continous RA/SN

Cb - Severe turb in and below, mod-heavy glaze icing, RA/SN/GR and possible TS and lightening.

Sc - light turb possibly moderate passing through inversion, light/mod rime icing if FZL low. Generally nil precip but very light RA possible.

Cu - mod/severe turb in and below, light/mod glaze icing just above FZL, possible SHRA/SN from TCu

St - light turb especially passing through inversion, usually nil ice unless FZL low then light rime ice, drizzle with reduced vis.

Question 53

Identify the following cloud sub-sets and outline the atmospheric conditions indicated by each:

(a) Asperitas
(b) Mammatus
(c) Altocumulus Lenticularis
(d) Rotor Cloud
(e) Kelvin Helmholtz waves
(f) Altocumulus Castellanus
(g) Banner cloud.

Answer 53

Asperitas

Likely form due to windshear manipulating the cloud, therefore associated with severe turbulence. May indicate more widespread severe turbulence with a northwest flow over the southern alps and the potential development of thunderstorms.

Mammatus

Individual pockets form due to the subsidence of cold air, these may last for 10 minutes but clusters of mamma may last from 15 minutes to a few hours.
Always associated with light-mod turbulence, if forming under a Cb anvil indicates severe turbulence within the Cb.

Altocumulus Lenticularis

Forms when stable air flows over a barrier such as a mountain range. Cloud will form if sufficient moisture is present such that as it is lifted it cools and condenses to form cloud. Hazards associated are turbulence, generally within a rotor zone, strong up and downdraughts, and possibe airframe icing.

Rotor cloud

Occur in same environment as lenticular cloud, form when fast moving air becomes trapped in a vortex spinning about a horizontal axis. If moisture is present the updraughting portion will form ragged constantly changing cloud. If dry, the rotor will still exist but it may not be indicated by cloud.

Kelvin-Helmholtz waves

Forms where there is a velocity difference across the interface between two fluids, in this case the two fluids are a warm layer overlying a cold layer of air both travelling in different directions, or in the same direction at different speeds. This causes the cold air to rise in billows penetrating the warm air while warm tongues push down into the cold layer resulting in a wave motion. The waves crest and break, the internal turbulence generated breaks down the waves and eventually destroys them. Turbulence is usually short lived but very severe.

Altocumulus Castellanus

Mid level convective cloud, indicating mid level instability. Moderate turbulence within the cloud, possible Cb/TS development within 12-24 hours.

Banner cloud

Orographically induced clouds that form on the lee side of sharply shaped mountain peaks. Form as wind flows over the peak creating a pocket of low pressure in the lee of the mountain, this redution in pressure results in the cooling and therefore condensation and cloud. It indicates the direction of the wind and mountain top level, it also indicates the presence of moisture at mountain top level. If the size of the banner is increasing or wisps of cloud form at lower levels this indicates the moisture content of the air is increasing and generally indicates rapidly detoriating weather especially in conjunction with falling pressures.

Question 54

Explain the cloud dispersal processes of:

(a) direct warming
(b) sinking of air
(c) mixing with clear air.

Question 55

Describe the Bergeron theory of rainfall development.

Question 56

Describe the Coalescence theory of rainfall development.

Question 57

List the factors that affect the fall rate of water droplets.

Answer 57

Gravity
Size/mass of drop
Speed of the up/down draughting air the drop is falling through

Question 58

Define ‘super-cooled water droplets.

Answer 58

Liquid water cloud droplets that exist below 0 degrees (c). Typically just above the FZL freezing nuclei are not abundant and therefore most clouds in the low-mid troposphere consist entirely of SCWD. As altitude increases <-20(c) freezing nuclei are more abundant and clouds consist mostly of ice crystals.

Question 59

Describe the formation process of
freezing rain.

Answer 59

Freezing rain begins with snow forming at mid-high level in the troposphere, this snow then falls into a warm layer below resulting in the snow melting. These drops remain at 0 (c) until the last of the ice crystals have melted but before they get the chance to begin to warm up, they fall into a sub-zero layer but do not immediately freeze. This is because the freezing nuclei that the ice crystals coalesced into snowflakes high in the atmosphere (-30 - -10c) are no longer suitable as freezing nuclei at temperatures only just below the freezing level.

Question 60

Interpret a graph of saturation water vapour content against temperature and calculate dew point and
relative humidity from the graph

Question 61

Explain why the SALR steepens with increasing height and increasing latitude.

Answer 61

As height and/or lat increases, the amount of moisture in the air decreases as it will generally precipitate out or form cloud. Therefore the air will tend to cool at the DALR of 3c/100ft rather than the SALR of 1.5c/1000ft.

Question 62

Describe the effect of latent heat release on stability inside a cloud and its influence on the resulting cloud type.

Answer 62

All formation of cloud releases latent heat into the environment, however if this occurs in an already stable parcel of air, the latent heat

Question 63

With regard to orographically developed cloud:

(a) explain the influence of stability/instability and different surface dew point values on the type and vertical extent of any cloud formed

(b) describe the formation and characteristics of lenticular cloud.

Question 64

State the areas of the globe where freezing rain is most likely to be encountered.

Answer 64

Continental climates with large mountain ranges. Canada, East USA, parts of Europe, Scandinavia, and Russia.