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Question 142-1 : Which forces are balanced with geostrophic winds ? [ Certification weather ]

Pressure gradient force coriolis force

Admin .we have a geostrophic wind when the pressure gradient force pgf is exactly balanced by coriolis force . 582

Question 142-2 : How does moderate turbulence affect an aircraft ?

Changes in altitude or attitude occur but the aircraft remains in positive control at all times

Admin .procedures for air navigation services air traffic management pans atm doc 4444 .instructions for air reporting by voice communications.moderate conditions in which moderate changes in aircraft attitude and/or altitude may occur but the aircraft remains in positive control at all times usually small variations in airspeed changes in accelerometer readings of 0 5 g to 1 0 g at the aircraft's centre of gravity difficulty in walking occupants feel strain against seat belts loose objects move about .severe conditions in which abrupt changes in aircraft attitude and/or altitude occur aircraft may be out of control for short periods usually large variations in airspeed changes in accelerometer readings greater than 1 0 g at the aircraft's centre of gravity occupants are forced violently against seat belts loose objects are tossed about exemple 246 Changes in altitude or attitude occur but the aircraft remains in positive control at all times.

Question 142-3 : Which degree of aircraft turbulence is determined by the following icao description .'there may be moderate changes in aircraft attitude and/or altitude but the aircraft remains in positive control at all times usually small variations in air speed changes in accelerometer readings of 0 5 to 1 0 g ?

Moderate

Admin .procedures for air navigation services air traffic management pans atm doc 4444 .instructions for air reporting by voice communications.moderate conditions in which moderate changes in aircraft attitude and/or altitude may occur but the aircraft remains in positive control at all times usually small variations in airspeed changes in accelerometer readings of 0 5 g to 1 0 g at the aircraft's centre of gravity difficulty in walking occupants feel strain against seat belts loose objects move about .severe conditions in which abrupt changes in aircraft attitude and/or altitude occur aircraft may be out of control for short periods usually large variations in airspeed changes in accelerometer readings greater than 1 0 g at the aircraft's centre of gravity occupants are forced violently against seat belts loose objects are tossed about exemple 250 Moderate.

Question 142-4 : In a land and sea breeze circulation the land breeze blows ?

During the night and is weaker than the sea breeze

Admin . 600 exemple 254 During the night and is weaker than the sea-breeze.

Question 142-5 : A high pressure area slack pressure gradient covers part of the mediterranean sea and coastal region during the summer what surface wind direction is likely at an airport at the coast on a sunny afternoon ?

Sea to land

Admin .during a sunny afternoon sea breeze is likely to occur . 601.we should expect a wind from the sea . 544 exemple 258 Sea to land.

Question 142-6 : A mountain breeze katabatic wind blows ?

Down the slope during the night

Admin .during the day the sun heats up valley air rapidly this causes it to rise causing a warm upslope wind valley breeze .at night the process is reversed mountain air cools rapidly at night and 'falls' downslope causing a wind going in the valley mountain breeze . 499.a mountain breeze and a valley breeze are two related localized winds that occur one after the other on a daily cycle exemple 262 Down the slope during the night.

Question 142-7 : Generally northern hemisphere winds at 5000 ft/agl are south westerly while most of the surface winds are southerly what is the primary reason of difference between these two wind directions ?

Friction between the wind and the surface

Admin .at low elevations friction will slow the air and hence the coriolis force will be less effective in its deflection of the wind . 561.as the elevation decreases the direction backs changes direction in an counter clockwise motion in northern hemisphere .at mid latitude over land wind speed in friction layer decrease by 50% angle between wind direction and isobars changes by 30° value to be used in examinations exemple 266 Friction between the wind and the surface.

Question 142-8 : Friction between the air and the ground results in the northern hemisphere in ?

Backing of the wind and decrease of wind speed at the surface

Admin .at low elevations friction will slow the air and hence the coriolis force will be less effective in its deflection of the wind . 561.as the elevation decreases the direction backs changes direction in an counter clockwise motion in northern hemisphere .at mid latitude over land wind speed in friction layer decrease by 50% angle between wind direction and isobars changes by 30° value to be used in examinations exemple 270 Backing of the wind and decrease of wind speed at the surface.

Question 142-9 : What degree of turbulence if any is likely to be encountered while flying through a cold front in the summer over central europe at fl 100 ?

Severe turbulence in cb cloud

exemple 274 Severe turbulence in cb cloud.

Question 142-10 : You are flying at 2500 ft/agl above ground level the wind is 180° and intend to land at an airport at sea level directly below from approximately which direction would you expect the surface wind mid latitude northern hemisphere ?

South southeast

Admin .at low elevations friction will slow the air and hence the coriolis force will be less effective in its deflection of the wind .in northern hemisphere at mid latitude over land wind speed in friction layer decrease by 50% the wind in the friction layer blows across the isobars towards the low pressure angle between wind direction and isobars changes by 30° value to be used in examinations .at 2500 ft you will be out of the friction layer on the ground the direction will be 180° 30° = 150° south southeast direction .in the northern hemisphere the friction layer decreases the wind direction anti clockwise exemple 278 South-southeast.

Question 142-11 : What units are used to report vertical wind shear ?

Kt/100 ft

exemple 282 Kt/100 ft.

Question 142-12 : What name is given to the jet stream lying across india a . 262 ?

Tropical jet stream

.tropical jet stream = tropical easterly jet = equatorial jet stream = the only one blowing from east to west during summer season . 533 exemple 286 Tropical jet stream.

Question 142-13 : An aircraft is flying through the polar front jet stream from south to north beneath the core how would the oat change in the northern hemisphere during this portion of the flight ?

It decreases

.the polar front jet stream runs from west to east and it will be found in the warm air of the ferrel cell sub tropical air mass . 575.if you cross below the jet stream northern hemisphere and you are flying from south to north then you are flying from the warm subtropical air into the colder polar air .the outside air temperature oat will decrease exemple 290 It decreases.

Question 142-14 : What is the average height of the arctic jet stream core ?

20000 ft

Admin .average height of the arctic jet 20000 ft .average height of the polar front jet 30000 ft .the artic jet is at a higher latitude than the polar front jet hence at a lower height tropopause is lower at the poles than the equator .arctic jet stream = 20000 ft .polar front jet stream = 30000 ft .subtropical jet stream = 40000 ft exemple 294 20000 ft .

Question 142-15 : What is the approximate ratio between height and width for a jet stream cross section ?

Ratio is 1/100

.for examination purposes we assume a jet stream to be about 2000 nm long 200 nm wide and 2 nm deep this gives an approximate ratio between height and width of 1/100 exemple 298 Ratio is 1/100.

Question 142-16 : Which jet stream blows all year round over the northern hemisphere ?

The subtropical jet stream

.the subtropical and polar front jets are present throughout the year .the polar night jet is only active during the winter months of the northern hemisphere and is located at 60° north .the equatorial jet is only present during the northern hemisphere summer exemple 302 The subtropical jet stream.

Question 142-17 : What is the average height of the jet core within a polar front jet stream ?

30000 ft

Admin .arctic jet stream = 20000 ft .polar front jet stream = 30000 ft .subtropical jet stream = 40000 ft . 595 exemple 306 30000 ft.

Question 142-18 : An aircraft is flying from south to north above the polar front jet stream at fl 400 in the southern hemisphere what change if any in temperature will be experienced ?

It decreases

Admin .flying from south to north in the southern hemisphere means that on crossing the polar front the aircraft will go from the cold air mass polar maritime to the warm air mass tropical maritime .at fl400 the aircraft will be above the tropopause .the tropopause in the warm air will be higher and colder than the tropopause in the cold air so the aircraft will note a decrease in temperature exemple 310 It decreases.

Question 142-19 : A wind speed of 350 kt within a jet stream core should be world wide regarded as ?

Possible but a very rare phenomenon

.the highest recorded jet stream speed 354 kt 656 km/h above isle of south uist scotland 13th december 1967 .the jet stream varies from about 80 to 350 nm wide and 1 to 3 nm thick its strongest winds are generally encountered at about 30000 feet .jet stream winds usually have a speed of 130 to 260 kt exemple 314 Possible but a very rare phenomenon.

Question 142-20 : An aircraft over western europe is crossing a jet stream 2500 ft below its core at right angles while crossing the outside temperature is increasing the prevailing wind is ?

From the right

.if the outside temperature is increasing while crossing below its core it's because you are flying from cold sector to warm sector .the wind comes from your right because if you stand with your back to the wind in northern hemisphere low pressure and low temperature are on your left exemple 318 From the right.

Question 142-21 : What is the main cause for the formation of a polar front jet stream ?

The north south horizontal temperature gradient at the polar front

Admin .fundamental to the formation of the polar front jet stream is the physical property that warm air is less dense than cold air when both are at the same pressure the polar front represents the boundary between higher latitude cold air and lower latitude warm air this temperature contrast extends from earth's surface up to the polar front jet stream altitude .air pressure is determined by the weight of overlying air in the vicinity of the polar front air pressure drops more rapidly with an increase in altitude in the more dense cold air than in the less dense warm air .the effect of temperature on air density results in air pressure at any given altitude being higher on the warm equatorward side of the polar front than on the cold poleward side when cold and warm air reside side by side the higher the altitude the greater the pressure difference is between the cold and warm air at the same altitude .across the polar front at upper levels including the jet stream altitude horizontal pressure differences cause air to flow from the warm air side of the front towards the cold air side of the front .once air is in motion it is deflected by earth's rotation coriolis effect upper level air flowing poleward from higher pressure towards lower pressure is deflected to the right in the northern hemisphere or to the left in the southern hemisphere the result is a jet stream flowing generally towards the east parallel to and above the polar front exemple 322 The north-south horizontal temperature gradient at the polar front.

Question 142-22 : Which jet stream is connected with a surface front system ?

The polar front jet stream

.the polar front is the boundary between polar air and tropical air . 595.you can see that the polar front jet stream is connected with the polar front for the other jetstreams there is no front for information easterly jet stream is the equatorial jetstream exemple 326 The polar front jet stream.

Question 142-23 : At approximately what flight level is the subtropical jet stream found ?

Fl 400

Admin .jet streams vary in height from 20000 ft to 40000 ft and can reach speeds of more than 240 kt . 595.the subtropical jet stream is located around 30°n .the subtropical jet stream can be found at fl400 40000 ft .arctic jet stream = 20000 ft .polar front jet stream = 30000 ft .subtropical jet stream = 40000 ft exemple 330 Fl 400.

Question 142-24 : Flight zurich to rome etd 1600 utc eta 1800 utc at what flight level would you first expect to encounter clear air turbulence on the climb out from zurich . 273 ?

Fl 220

. 522.cat area n°2 shows moderate cat between fl220 and fl400 exemple 334 Fl 220.

Question 142-25 : At what flight level is the jet stream core that is situated over northern scandinavia . 274 ?

Fl 280

. 525.the jet stream flight level is indicated below his position maximum jet stream wind speed is 135 kt exemple 338 Fl 280.

Question 142-26 : Select from the map the wind for the route zurich london at fl 280 . 277 ?

220/60

Admin . 527.225°/95 kt.220°/55 kt.210°/40 kt.255°/35 kt.average wind is 227°/56 kt .in northern hemisphere wind turns clockwise with height and speed increases it means that normally at fl280 chart is for fl300 we should expect a wind of 220°/50 kt anyway answer 220/60 remains the only valid answer exemple 342 220/60.

Question 142-27 : What name is given to the jet stream lying over north africa b . 280 ?

Sub tropical jet stream

.the subtropical jet stream is located around 30°n/s . 590 exemple 346 Sub-tropical jet stream.

Question 142-28 : What wind is forecast at fl 390 over paris . 281 ?

210°/40 kt

Admin . 528.the wind is blowing with a south south west component west of paris and speed is reducing from 45 kt to 30 kt close to luxembourg .'210°/40 kt' is the correct answer exemple 350 210°/40 kt.

Question 142-29 : What is the direction and maximum speed of the jet stream affecting the route between munich and london . 285 ?

220° / 120 kt

. 529 exemple 354 220° / 120 kt.

Question 142-30 : Flight from bordeaux to amsterdam eta 2100 utc at eta amsterdam what surface wind is forecast .taf eham 281500z 281601 14010kt 6000 ra sct025 becmg 1618 12015g25kt sct008 bkn013 tempo 1823 3000 ra bkn005 ovc010 becmg 2301 25020kt 8000 nsw bkn020 = ?

120° / 15 kt gusts 25 kt

Admin .becmg becoming indicates a change to forecast conditions is expected to occur slowly within the period designated in the time group immediately following the heading .the duration of this change is normally about 2 hours the elements included in the becmg line will supercede some of the previous taf groups but it is possible all the groups may change .any group omitted in the becmg line will be the same during the becmg period as indicated in the main taf line .in this question the wind becoming 120°/15 kt gusts 25 kt 12015g25kt between 16h and 18h it will remain unchanged until 23h .then the wind becoming 250°/20kt between 23h and 01h exemple 358 120° / 15 kt gusts 25 kt.

Question 142-31 : The equatorial easterly jet is a jet stream that occurs ?

Only in the summer of the northern hemisphere at approximately 45 000 ft

.this jet occurs in the northern summer between 10°n and 20°n chiefly over or just to the south of high land masses such as in asia and africa its occurrence is due to a temperature gradient with colder air to the south which produces sufficient temperature differential above 45000 ft to give wind speeds of over 100 kt .because colder temperatures at height are to the south it is an easterly jet this jet is now more usually known as the tropical easterly jet perhaps more correctly as it lies some distance from the equator . 533 exemple 362 Only in the summer of the northern hemisphere at approximately 45 000 ft.

Question 142-32 : In which zone of a polar front jet stream is the strongest cat to be expected ?

On the polar air side of the core

.the strongest cat is in the warm tropical air but on the cold polar air side of the core exemple 366 On the polar air side of the core.

Question 142-33 : What is the minimum speed for a wind to be classified as a jet stream ?

60 kt

.the heavyline line delineating the jet axis begins/ends at the points where a wind speed of 30 m/s 60 kt is forecast exemple 370 60 kt.

Question 142-34 : A wind sounding in the region of a polar front jet stream gives the following windprofile northern hemisphere .900hpa 220/20kt.800hpa 220/25kt.700hpa 230/35kt.500hpa 260/60kt.400hpa 280/85kt.300hpa 300/100kt.250hpa 310/120kt.200hpa 310/80kt.which system is the jet stream associated with ?

With a warm front

.the highest wind speed is in the core of the polar front jet stream at 250 hpa approximately fl340 in the northern hemisphere the cold front jet is from the sw and the warm front jet is from the nw .at fl340 the jet direction is 310° it is a north west direction exemple 374 With a warm front.

Question 142-35 : What is the most significant difference between an equatorial jet stream and all the other jet streams ?

Wind direction

.its wind direction is from east to west .this jet occurs in the northern summer between 10°n and 20°n chiefly over or just to the south of high land masses such as in asia and africa .because colder temperatures at height are to the south it is an easterly jet this jet is now more usually known as the tropical easterly jet perhaps more correctly as it lies some distance from the equator . 533 exemple 378 Wind direction.

Question 142-36 : You cross a jet stream in horizontal flight at approximately right angles while crossing in spite of a strong wind of 120 kt you notice the temperature barely changes which of the following statements is correct ?

This phenomenon is absolutely normal as you are crossing the jet core

exemple 382 This phenomenon is absolutely normal as you are crossing the jet core.

Question 142-37 : What jet streams are likely to be crossed during a flight from stockholm to rio de janeiro 23°s at fl 350 in july ?

A polar front jet stream followed by one or two subtropical jet streams

Admin . 2535 exemple 386 A polar front jet stream followed by one or two subtropical jet streams.

Question 142-38 : While crossing a jet stream at right angles in western europe 3000 ft below its core and oat is decreasing what would be the prevailing wind ?

Crosswind from the left

.if you are moving to an area of decreasing temperature then you must be moving from an area of warm air to cold and in the northern hemisphere the frontal jetstream which is just underneath the warm sector tropopause in the warm sector close to the front blows with the cold sector to its left therefore if you are crossing to the cold sector the jet is blowing from the left . 595 exemple 390 Crosswind from the left.

Question 142-39 : During the winter months in mid latitudes in the northern hemisphere the polar front jet stream moves toward the ?

South and speed increases

.in winter the polar front moves south . 585.during summer it moves north . 598.winter speed 130 to 150 kt .summer speed 60 to 100 kt exemple 394 South and speed increases.

Question 142-40 : What causes surface winds to flow across the isobars at an angle rather than parallel to the isobars ?

Surface friction

Admin .friction is a force it is a force that slows motion and dampens energy .in meteorology friction is important because it causes the wind speeds at the surface to be less and more turbulent than they otherwise would be rough terrain is more effective in decreasing the wind speed than a water surface friction processes can help promote surface convergence and uplift .resistance to movement of air flowing along the surface of the earth induces the wind to flow across the isobars at an angle exemple 398 Surface friction.


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