ATPL Meterology

Question 1

Briefly explain the purpose of and the types of met info available to international aviation through the world area forecast system (WAFS) ???

Answer 1

The world area forecast system (WAFS) is a worldwide system by which world area forecast centres (WAFCs) provide aeronautical met en route forecasts in uniform standardised formats.
This includes forecasts of upper winds, temperatures , humidity, max wind, icing, turbulence and CB cloud.
The two WAFCs also provide forecasts of significant weather (SIGWX) including tropical

Question 2

Convert between Celsius, Fahrenheit and absolute temperature

Answer 2

To convert temperatures in degrees Fahrenheit to Celsius, subtract 32 and multiply by .5556

To convert Celsius to Fahrenheit multiply by 1.8 and add 32

Absolute temperatures are expressed in degrees kelvin. 0°C is equal to 273 Kelvin (100°C equals 373 Kelvin)

Question 3

Explain what is meant by the terms solar radiation

Answer 3

Solar radiation: virtually all the atmospheric energy, including that required for heating of air, is derived from the sun, which is essentially a huge nuclear reactor. The solar energy produced by the sun falls within a wavelength range of 0.5u to 4.0u (u is a micrometer also known as a micron). Because of the very high source temperatures involved, solar energy is short wave radiation. Solar energy is made up of ultraviolet, visible light, infrared

Question 4

What percent of ultraviolet makes up solar energy

Answer 4

Approximately 9%
Ultraviolet radiation is largely absorbed by the ozone contained in the stratosphere while a large part of the visible radiation is absorbed by water vapour. Also CO2 absorbs a very small percentage of incoming radiation

Question 5

What percent of visible light is solar energy made up of

Answer 5

45%

Question 6

What percent of infrared makes up solar energy

Answer 6

46%

Question 7

How much solar radiation does the earth receive

Answer 7

Because of the large distance from the sun, earth receives only about 0.0005% of the total solar radiation emitted into space. Of this minuscule amount, some radiation is reflected back into space by cloud tops while particles within the atmosphere prevent some solar radiation reaching the earth surface due to the effect of scattering. Although this scattering process expels some radiation into space again, some is redirected to earth. The latter is known as sky radiation, thus the total solar radiation received by earth is the sum of sky radiation and direct radiation, called cloak solar radiation

Question 8

What’s the basis of the huge convective cell (Hadley cell)

Answer 8

The rising air spreads pole ward at high levels but because of the coriolis force it does not travel all the way to the poles and as a consequence it sinks towards the surface in the belt of sub tropical highs in each hemisphere. The surface air then moves towards the equator as the trade winds, blowing from the southeast and the northeast in the southern and northern hemisphere respectively

Question 9

What are the doldrums in the Hadley cell

Answer 9

A zone of ascending air within the regions at or near the meteorological equator caused by convective action from warm surfaces. These regions contain the equatorial trough and are referred to as the doldrums

Question 10

What are the horse latitudes in the Hadley cell

Answer 10

Subsiding air within the regions covered by the semi stationary anticyclones centred at average latitudes 30°N and 30°S. These regions are referred to as the horse latitudes

Question 11

When is the worst month for tropical cyclones in the Southern Hemisphere

Answer 11

February

Question 12

What is the airflow over the equatorial regions in the Hadley cell

Answer 12

High level divergence over equatorial regions and high level convergence over the anticyclonic regions

Question 13

What are the trade winds in the Hadley cell

Answer 13

Low level air flows (winds) from the anti cyclonic regions towards the equatorial trough. These winds are known as the trade winds

Question 14

What is the equatorial trough

Answer 14

The heated surfaces at or near the thermal equator produce a high degree of instability and convection so that the main thrust of air movement within the affected regions is upward. This results in the establishment of the equatorial trough, a system of comparative low pressure and surface convergence

Question 15

What cloud development is found in the equatorial trough

Answer 15

Since the surfaces which the equatorial trough move have vast amounts of oceanic areas, considerable cloud formations are involved. These formations (which can at time penetrate into the stratosphere) reflect a certain percentage of solar radiation, which would have an adverse effect on the degree of surface heating if the main cloud concentration were positioned at the thermal equator. Maximum convergence, convection and cloud development are normally located a few degrees of latitude away from the equatorial trough on the geostrophic equator side

Question 16

What do the trade winds produce in the equatorial trough

Answer 16

The trade winds which converge within the equatorial trough, will frequently produce the intertropical convergence zone (ITCZ)

Question 17

What is the equatorial trough a permanent feature of

Answer 17

The equatorial trough is a more or less permanent feature of convergence and convection whereas the ITCZ is an erratic feature, the presence and intensity of which depends on the variable degree of trade wind convergence. Put differently, the equatorial trough is a general term for the belt of comparatively low pressure around the globe in the tropics. The ITCZ is a synoptic or weather feature inside this trough

Question 18

What are the latitudes covered by the equatorial trough called

Answer 18

The latitudes covered by the equatorial trough are known as the doldrums. Within these areas, winds are generally light and variable mainly due to the fact that the predominant movement of air is upward rather than horizontal. The convergence associated with the doldrums is not of a constant nature

Question 19

Where is the equatorial trough located during the northern summer (May to October)

Answer 19

The entire trough is located in the northern hemisphere but, due to the strongly differing nature of the surface, the latitudinal change in position and intensity of the trough varies greatly. Over the major oceanic regions, the equatorial trough is fairly constant in terms of latitude but the influence of continental land masses, their differing mountainous natures and local pressure systems cause the trough to shift considerably and even fracture in a few localities

Question 20

What can cause the fractures in the ITCZ (in the northern summer)

Answer 20

The influences of heat lows, monsoons and orographic factors in the India/into china region causes an almost complete fracture while the nature of the trough alters dramatically over North Africa

Question 21

Where is the equatorial trough in the Southern summer (November to April)

Answer 21

A large deflection takes the trough south through South Africa while a smaller wave brushes over the northern parts of Australia for similar reasons as stated for the northern hemisphere i.e influence of variations in surface characteristics. The major difference however, is the position of the trough in the central Pacific and Atlantic oceans where the equatorial trough remains in the northern hemisphere. The main reasons for this are firstly, stronger trade wind strength in the northern compared to the Southern Hemisphere and, secondly, the influence of oceanic surface temperatures

Question 22

What speed to changes occur with weather in the ITCZ

Answer 22

Changes in activity take place suddenly and dramatically

Question 23

What does the zone of an active ITCZ become covered with

Answer 23

Considering the high moisture content of air especially when the ITCZ is positioned over oceanic regions, any lifting will almost immediately involve the SALR when air saturates at low levels. Thus the zone becomes associated with massive cloud developments, which can involve a horizontal width of some 5 to 600km and a depth of some 50,000 to 60,000ft

Question 24

What does the cloud consist of in an active ITCZ

Answer 24

Cloud consists mainly of the cumulus type such as CU, CB and AC but also some stratiform cloud at high levels (CS) where tops of CB clouds reach a balance with the surrounding cold air. It is not uncommon for tops of CBs to exceed the height of the equatorial tropopause through simple momentum

Question 25

What are the main dangers of an active ITCZ

Answer 25

Turbulence, icing and other factors associated with CBs

Question 26

How is turbulence a danger in an active ITCZ

Answer 26

The presence of large numbers of CB clouds in their various stages of development means that turbulence will be moderate to severe. The width of the ITCZ when active can be up to 600km, thus penetration will involve prolonged exposure to turbulence. It will be difficult to avoid this phenomenon unless the flight path can be maintained above the tops of CBs

Question 27

How is attempting to avoid turbulence by flying below the base of CBs potentially dangerous because most often flight will have to be below 1000ft where the following problems are encountered

Answer 27

- heavy precipitation will seriously reduce visibility - depending on the stage of development, strong up or downdraughts can be expected below the cloud base - strong convergence below growing cells will reduce ambient pressure with the result that the altimeter will overhead

Question 28

How is icing a danger in a active ITCZ

Answer 28

The high water content experienced in ITCZ cloud developments poses a risk of moderate to severe icing above the freezing level and especially within the first 10,000ft to 15,000ft above it

Question 29

What are other CB factors that are dangers of an active ITCZ

Answer 29

Exposure to dangers of thunderstorms. When the ITCZ extends over continental areas, its characteristics will be influenced by the nature of the land, the temperature differences of the air masses either side of the zone and the presence of major airflows.

Question 30

What is the weather associated with an inactive ITCZ

Answer 30

When inactive, the zone is associated with various oktas of cumulus and some shower activity from the more developed clouds. Winds are light and variable

Question 31

What is the South Pacific convergence zone (SPCZ)

Answer 31

A zone of intense cloudiness due to convergence of two major airflows is frequently identified from the eastern tip of Papua New Guinea to slightly southeast of French Polynesia. Like the ITCZ, it varies in intensity

Question 32

Where do the two converging airflows originate from in the SPCZ

Answer 32

- the semi stationary anticyclonic system in the eastern Pacific. The easterlies on the equator side of the system turn north easterly on approaching the western pacific; and - the anticyclones originating and travelling eastwards from the Australia/ New Zealand region the south-easterlies preceding these systems extend to the region where the SPCZ forms

Question 33

When is the SPCZ more active

Answer 33

When the north easterlies and the south easterlies meet they form a convergence zone with weather characteristics similar to the ITCZ. The zone is more active in summer than winter

Question 34

What strengthens or re activates the SPCZ

Answer 34

The SPCZ appears to be associated with the northeast passage of mid latitude cold fronts when the cloud band of the latter merges with that of the convergence zone. This cold fronts appear to strengthen or re activate the SPCZ

Question 35

Where is the northern limit of the SPCZ

Answer 35

The northern limit of the SPCZ is often taken to lie over Papua New Guinea and fluctuations in its intensity may bring cloudiness and rainfall down into Australia's Northern Territory and northern Queensland from time to time. It is this occurrence that may seem to indicate incorrectly that the ITCZ extends to Australia

Question 36

Where are the semi permanent anticyclones preferred to reside most of the year

Answer 36

There are a number of preferred localities at the western sides of major continents where almost permanent anticyclones reside most of the year. These systems are centred around latitudes 30°N and 30°S. In addition to these and involving the same latitudes are anticyclones that slowly travel eastwards (horse latitudes)

Question 37

What are the horse latitudes

Answer 37

The centres of the large semi permanent anticyclones are invariably associated with calm conditions, which are referred to as the horse latitude

Question 38

What do the semi permanent anticyclones have a strong influence on

Answer 38

Tropical weather due to their continuous surface divergence

Question 39

How high are the trade winds restricted to

Answer 39

The general outflow from the high pressure belts at average latitudes 30°N and 30°S towards the equatorial trough produce steady wind in the lower troposphere, generally restricted to approx 8,000ft AMSL. Even though the coriolis factor is weak in subtropical latitudes, it is sufficiently effective to produce bending to these winds

Question 40

What way do the Tradewinds go in both hemispheres

Answer 40

In the Southern Hemisphere equator bound airflow becomes southeasterly. In the northern hemisphere the equator bound airflow becomes a north easterly. These predominant winds are known as the trade winds and these are the winds that converge at the equatorial trough and are instrumental in producing the weather associated with the trough

Question 41

What is the strength of trade winds

Answer 41

Trade winds are quite steady and persistent in strength. In the pacific region they vary throughout the year from 10kts to 20kts with the occasional increase to 30kts. In global terms, the trade winds are generally slightly stronger in winter than summer. The wind above the trade winds are usually from the west, often light

Question 42

What are the variations in trade winds caused by

Answer 42

Although their direction in the Southern Hemisphere is mainly from the southeast there are minor variations in direction due to underlying terrain (islands versus oceans for instance) and pressure gradient fluctuations

Question 43

How is a subsidence inversion created from trade winds

Answer 43

Since these winds are fundamentally associated with the anticyclonic systems it is to be expected that subsidence, normally present in these systems, will influence the weather characteristics within the trade wind zone. However, as the winds travel further from the highs towards the equatorial trough and penetrate increasingly warm surface conditions, the effect of this subsidence lessens. Thus the weather, especially at the source of the trade wind zone, is for a large part influenced by subsidence inversions, which vary in height from 6,000ft to 8,000ft above sea level

Question 44

What are the conditions like below the trade wind subsidence inversion

Answer 44

Below the inversion, visibility is usually fair to good with varying amounts of cumulus with bases between 2,000 and 3,000ft and tops at some 8,000ft. These amounts and vertical limits are prone to increase when trade winds cross the windward side of islands so that increased wind speed and shower activity are likely in those localities

Question 45

What is the moisture content like below the trade wind subsidence inversion

Answer 45

The moisture content below the subsidence inversion is much greater than that above. Thus altitudes above some 8,000ft are characterised by good visibility and generally dry air and clear skies. However, as the trade winds approach the vicinity of the equatorial trough, the subsidence inversion weakens and rises in height. Increased instability from warm surfaces and, especially over ocean areas, great abundance of moisture, cause the formation and development of instability cloud which ultimately includes towering cumulus with associated thunder, squall and shower activity

Question 46

What happens when Southern Hemisphere trade winds cross the equator

Answer 46

Trade winds converging at the equatorial trough are subject to directional change depending on season. For instance, in mid Pacific, the trough never enters the Southern Hemisphere, which means that the south east trade winds (of the Southern Hemisphere) cross the equator to flow to the trough (in the northern hemisphere)

Question 47

What happens when the northern hemisphere trade winds cross the equator

Answer 47

During the Southern winter, the equatorial trough is in the northern hemisphere north of Australia so that trade winds in that region also cross the equator. However, in summer time in Australia, the trough is south of the equator so that the northern hemisphere trade winds will have to do the crossing

Question 48

How does the coriolis force affect the moving trade winds en route to the equatorial trough in the northern hemisphere

Answer 48

When the south east trade winds cross the equator en route to the equatorial trough in the northern hemisphere, they will be subjected to the coriolis force applicable to the northern hemisphere i.e veer to the right. The strength of the force is weak but still present. Therefore, after crossing the equator, the trade winds blow initially towards the trough from the south and ultimately from the southwest

Question 49

How does coriolis force affect the trade winds when its crossing the equator towards the trough near Australia

Answer 49

The north east trade winds from the northern hemisphere crossing the equator towards the trough near northern Australia in summer will initially become northerly and ultimately north west

Question 50

What are the influences of islands on the trade winds

Answer 50

In summertime, the land of major islands warms to a greater degree than the surrounding seas so that sea breeze effects develop over the land. Air pressure will be slightly lower over the land than over the sea and instability increased. Thus coastal regions exposed to the southeast experience an increase in cloud development and possibly heavy precipitation depending on the nature of terrain. In some situations this effect will be felt even at the lee side of islands

Question 51

What is the influence of islands on Tradewinds in the winter

Answer 51

In wintertime, the land is colder than the surrounding seas so that pressures are somewhat higher inland and stability is enhanced. Although some cloudiness may still occur at the southeast coasts from exposure to the Tradewinds, generally conditions are much drier and more stable

Question 52

What are the main disturbances in the tropical circulation

Answer 52

Individual cumulus, mesoscale convective areas (MCAs), wave disturbances, monsoons and tropical cyclones

Question 53

How is individual cumulus a tropical disturbance

Answer 53

These are the smallest disturbances, measure in a life span of only a few hours and a dimension of some 5km across, resulting from turbulence experienced in the trade wind friction layer. These individual clouds often align themselves in cloud streets more or less parallel to the wind direction, or they are arranged in honeycomb patterns

Question 54

How is mesoscale convective areas (MCAs) a tropical disturbance

Answer 54

These are systems comprising of grouped clusters of cumulus and CB developments within areas from 100km to 1,000km across. MCAs are characterised by instability through deep layers - they can often be part of the equatorial trough. Although many MCAs last no longer than one or two days, others can persist for extended periods of time

Question 55

What are wave disturbances

Answer 55

Apart from tropical cyclones, it is rare for closed circulation disturbances to appear in tropical latitudes. Instead, disturbances demonstrates themselves in wave form in the equatorial easterlies where waves travel from the east to the west but not necessarily at the same speed as the trade winds

Question 56

How do wave disturbance generally originate

Answer 56

The formation of a wave generally originates some two to four degrees of latitude on the pole ward side of the equatorial trough. Of all the wave disturbances that from in the tropical throughout a year, approx 25% develop to the tropical depression stage while some 10% become named tropical cyclones. Easterly waves are more frequent in the northern hemisphere than in the South Pacific

Question 57

What's the life span of easterly waves

Answer 57

Easterly waves normally have a life span of about 10 days, have an average wavelength of some 3,000km, travel approx 6 degrees in longitude per day and slope eastwards with height

Question 58

What will happen in wave disturbances when the easterly wind is greater than the speed of the wave

Answer 58

A region of convergence lies behind the wave while a region of low level divergence lies in front of the wave. Thus within the convergent zone behind the wave it is common to see well developed CB clouds with heavy showers and thunderstorm activity while ahead of the air is relatively clear. The system is almost identical to the mid latitude cold front -the sequence of events are the same

Question 59

What will happen to the wave disturbances when the speed of the easterly wind is slower than the speed of the wave

Answer 59

The region of convergence and cloudiness is found ahead of the wave and surface divergence coupled with relatively clear skies behind the wave

Question 60

What causes monsoons

Answer 60

When large land masses of the world heat up during their summer season, intense instability and convection cause air to rise so that replacement air from the oceans travel towards the land and inland. The great water content of this air produces large cumulus developments so that thunderstorms, heavy precipitation and squalls result. Mountain barriers accentuate the development. This is the basis of the large scale wind regime of the wet monsoon, which may well involve winds contradicting the prevailing wind

Question 61

What is the dry monsoon

Answer 61

When land masses cool in winter, subsidence on a grand scale over the land causes air to flow outward towards the oceans, which have retained a great deal of their stored heat. Thus the weather over the land is generally clear due to adiabatic warming. This reflects the dry monsoon

Question 62

Where are the major monsoon regions found

Answer 62

With the exception of perhaps the north Australian continent, the major monsoon regions are found in the northern hemisphere. The most developed monsoon winds are concentrated along the South Asian continent when in summer time the transport of moist air from the Indian Ocean causes widespread precipitation and cloudiness in India, Pakistan, Myanmar etc.

Question 63

When does the wet season for monsoons start

Answer 63

The wet season begins around June and ends towards late September. In the case of India for instance, about 75% of its annual rainfall is concentrated within this monsoon period

Question 64

Where are monsoon depressions frequent

Answer 64

In the Bay of Bengal region. These are systems extending up to some 25,000ft and lasting about three days on average. It appears these depressions have a strong influence on the distribution of monsoonal rain

Question 65

What is the predominant wind direction of the south Asian monsoon

Answer 65

From the south southwest but local topography has strong influences

Question 66

When does the wet monsoon take effect in Australia

Answer 66

In Australia the wet monsoon takes effect in December and peaks during February. During this period, heavy precipitation and thunderstorm conditions may prevail for many days. In the dry winter season, the weather in northern Australia is governed by the southeast trade winds, which are generally dry

Question 67

Pressure at sea level

Answer 67

1,000hPa

Question 68

Pressure at FL100 (10,000ft)

Answer 68

700hPa

Question 69

Pressure at FL185 (18,500ft)

Answer 69

500hPa

Question 70

Pressure at FL300 (30,000ft)

Answer 70

300hPa

Question 71

Pressure at FL340 (34,000ft)

Answer 71

250hPa

Question 72

Pressure at FL380 (38,000ft)

Answer 72

200hPa

Question 73

Pressure at FL445 (44,500ft)

Answer 73

150hPa

Question 74

Pressure at FL520 (52,000ft)

Answer 74

100hPa

Question 75

Polar jet stream wind direction

Answer 75

West

Question 76

Subtropical jet stream wind direction

Answer 76

West

Question 77

Equatorial jet stream wind direction

Answer 77

East

Question 78

Average height of jet streams (hPa)

Answer 78

Polar: 300 Subtropical: 200 Equatorial: 100

Question 79

Average wind velocity of jet streams (kts)

Answer 79

Polar: 70kts Subtropical: 100kts Southern Hemisphere, 300kts northern Equatorial: 40kts (winter)

Question 80

Maximum velocity of jet streams (kts)

Answer 80

Polar: 200 Subtropical: 250 Equatorial: 100

Question 81

Location (latitude) of the polar jet stream

Answer 81

40-60 degrees but may exceed these values at times

Question 82

Location (latitude) of the subtropical jet stream

Answer 82

25-35 degrees

Question 83

Location (latitude) of the equatorial jet stream

Answer 83

10-20 degrees north and south

Question 84

Characteristics of the polar jet stream

Answer 84

Normally associated with the polar front and especially in the northern hemisphere, will shift position seasonally. Bending is a very common occurrence

Question 85

What are the characteristics of the subtropical jet streams

Answer 85

Vertically above the subtropical highs and less subject to bending

Question 86

What are the characteristics of the equatorial jet stream

Answer 86

Stronger in summer than in winter. Since its max speed is commonly less than 60kts it is considered more a wind max than a jet

Question 87

Cold front pressure

Answer 87

Decrease Arrest or fall Increase

Question 88

Temperature cold front

Answer 88

Steady warm Often an abrupt decrease Steady cold

Question 89

Wind in cold front

Answer 89

Slight veering and increase in strength Sudden backing, may be associated with a squall Steady direction, slow decrease in strength

Question 90

Cloud in warm front

Answer 90

Possibly some CS or AS CU, CB and NS depending on type of front Clearance may be rapid, then isolated CU and CB

Question 91

Precipitation in cold front

Answer 91

Not common Showers possibly heavy, may include hail Showers may cease quickly, then isolated showers

Question 92

Visibility in cold front

Answer 92

Fair to good Very poor Very good but reduced in showers

Question 93

Dew point in cold front

Answer 93

No change Increase due to precipitation Lower than dew point in advance of the front

Question 94

Relative humidity in cold front

Answer 94

Lower than relative humidity in advance of the front

Question 95

Pressure in warm front

Answer 95

Decrease Arrest or fall Steady or slight rise

Question 96

Temperature in warm front

Answer 96

Steady or slight decrease due to precipitation Increase Little change

Question 97

Wind in warm front

Answer 97

Veer and slight increase in strength Backing Fairly steady in direction and speed

Question 98

Cloud in warm front

Answer 98

CI,CS,AS,NS patches AT,SC. May include CU,CB depending on type ST,NS. May include CU,CB depending on type No high level cloud but low level cloud may persist

Question 99

Precipitation in warm front

Answer 99

Light rain turning to persistent heavy rain Rain ceases but may change to drizzle Occasional rain or drizzle

Question 100

Visibility in warm front

Answer 100

Good but becoming poor in rain Very poor Fair but poor in drizzle/rain

Question 101

Dew point in warm font

Answer 101

Slight increase Steady Higher blue than before the warm front

Question 102

Relative humidity in warm front

Answer 102

Increase Very high Higher value than before the warm front

Question 103

Nitrogen

Answer 103

78.08%

Question 104

Oxygen

Answer 104

20.94%

Question 105

Argon

Answer 105

0.94%

Question 106

Carbon dioxide

Answer 106

0.03%

Question 107

Neon

Answer 107

0.001%

Question 108

Helium hydrogen, xenon, ozone etc.

Answer 108

0.009%

Question 109

Temp pressure at sea level

Answer 109

+15° 1013

Question 110

Temp pressure at 5,000ft

Answer 110

+5° 843

Question 111

Temp pressure at 10,000ft

Answer 111

-5° 697

Question 112

Temp pressure at 15,000ft

Answer 112

-15° 572

Question 113

Temp pressure at 20,000ft

Answer 113

-25° 456

Question 114

Temp pressure at 25,000ft

Answer 114

-35° 377

Question 115

Temp pressure at 30,000ft

Answer 115

-45° 301

Question 116

Temp pressure at 35,000ft

Answer 116

-55° 239

Question 117

Temp pressure at 36090ft

Answer 117

-56.5 226.3

Question 118

Temp pressure at 40,000ft

Answer 118

Constant and 188hPa

Question 119

Calculating feet per hectopascal

Answer 119

Ft per hectopascal = 96T / p T is absolute temperature (273 kelvin) P is the ambient pressure in hPa

Question 120

Satellite imagery cloud tops dark grey

Answer 120

Up to FL050

Question 121

Satellite imagery cloud tops light grey

Answer 121

FL050 to FL100

Question 122

Satellite imagery cloud tops blue

Answer 122

FL100 to FL200

Question 123

Satellite imagery cloud tops green

Answer 123

FL200 to FL300

Question 124

Satellite imagery cloud tops yellow

Answer 124

FL300 to FL400

Question 125

Satellite imagery cloud tops red

Answer 125

FL400 to FL450

Question 126

Satellite imagery cloud tops purple

Answer 126

Higher than FL450

Question 127

What are solstices

Answer 127

Due to the tilted earth spin axis, the latitude where solar input is perpendicular shifts north and south. The vertical sun is at its most northern latitude (23 degrees north) in June and at its most southern latitude (23 degrees south) in December. These dates are known as the solstices

Question 128

What are the equinoxes

Answer 128

Hours of daylight and dark are equal all over the world when the perpendicular sun is exactly over the geographical equator. This occurs twice a year, on or about 22 March and 22 September; these dates are known as the equinoxes

Question 129

What is the wavelength of solar radiation.

Answer 129

The solar energy produced by the sun falls within a wavelength range of 0.5u to 4.0u (u is a micrometer, also known as a micron). Solar energy is short wave radiation

Question 130

What is the wavelength of terrestrial radiation

Answer 130

Terrestrial radiation is long wave, low frequency band, between 4u and 80u

Question 131

Wind and temp prognosis chart FL050

Answer 131

850hpa

Question 132

Wind and temperature prognosis charts FL100

Answer 132

700hPa

Question 133

Wind and temp prognosis chart FL140

Answer 133

600hPa

Question 134

Wind and temp prognosis chart FL185

Answer 134

500hPa

Question 135

Wind and temp prognosis chart FL240

Answer 135

400hPa

Question 136

Wind and temp prognosis chart FL300

Answer 136

300hPa

Question 137

Wind and temp prognosis chart FL340

Answer 137

250hPa

Question 138

Wind and temp prognosis chart FL385

Answer 138

200hPa

Question 139

Wind and temp prognosis chart FL445

Answer 139

150hPa

Question 140

Wind and temp prognosis chart FL530

Answer 140

100hPa

Question 141

Define the phenomenon known as soft hail (also known as graupel or snow pellets) (GS for graupel)

Answer 141

Graupel also called soft hail or snow pellets, is precipitation that forms when supercooled droplets of water are collected and freeze on falling snowflakes, forming 2–5 mm (0.08–0.20 in) balls of rime.

Question 142

Wind and temp prognosis chart FL050

Answer 142

850hpa

Question 143

Wind and temperature prognosis charts FL100

Answer 143

700hPa

Question 144

Wind and temp prognosis chart FL140

Answer 144

600hPa

Question 145

Wind and temp prognosis chart FL185

Answer 145

500hPa

Question 146

Wind and temp prognosis chart FL240

Answer 146

400hPa

Question 147

Wind and temp prognosis chart FL300

Answer 147

300hPa

Question 148

Wind and temp prognosis chart FL340

Answer 148

250hPa

Question 149

Wind and temp prognosis chart FL385

Answer 149

200hPa

Question 150

Wind and temp prognosis chart FL445

Answer 150

150hPa

Question 151

Wind and temp prognosis chart FL530

Answer 151

100hPa

Question 152

Define the phenomenon known as soft hail (also known as graupel or snow pellets) (GS for graupel)

Answer 152

Graupel also called soft hail or snow pellets, is precipitation that forms when supercooled droplets of water are collected and freeze on falling snowflakes, forming 2–5 mm (0.08–0.20 in) balls of rime.

Question 153

Which way will upper winds orientate themselves

Answer 153

In mid latitudes of both hemispheres the resulting strong upper winds will orientate themselves more or less west-east because the overriding thermal gradient axis is generally north-south (from equator to both poles)

Question 154

Where will jet streams develop as a result of strong upper winds

Answer 154

As a result of the strong upper winds, jet streams will often develop in the vicinity of the tropopause. These air streams are high velocity winds contained in a tunnel like fashion and flowing generally from west to east

Question 155

What's the definition of a jet stream

Answer 155

A strong narrow current of air, concentrated along a quasi horizontal axis in the upper troposphere or in the stratosphere, characterised by strong vertical and horizontal windshear and featuring one or more wind maxima. The wind strength must be greater than 60kts

Question 156

What are the factors that jet streams have in common

Answer 156

The centre of the jet, the core, is always situated above a zone of strong horizontal temp gradient, although this gradient does not necessarily extend to low levels; and above the level of maximum wind the temperature gradient is reversed

Question 157

What happens to the tropopause near the jet stream

Answer 157

Near the jet stream there is a rapid change in the height of the topopoause; it is high over the warm air mass and low over the cold air mass. The tropopause may fracture or slope down rapidly (often the case with sub tropical jet streams)