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For a similar pressure gradient the geostrophic wind speed will be ?

Preparation > civilian

exemple reponse 239
Greater at 3 °n than at 6 °n. to have a geostrophic wind we need to have a pressure gradient force coriolis force (create earth's rotation depending on geographic latitude) we need to have two differents air mass to have a pressure gradient force (pgf) since earth rotates objects that are above earth apparently move or are deflected if they are already moving owing to it's rotation this apparent motion caused the coriolis force in northern hemisphere objects will be deflected to their right while in southern hemisphere objects will be deflected to their left the magnitude of deflection also a function of distance from equator velocity so farther from equator object is greater deflection the faster an object moving greater deflection these 'object can be anything from airplanes to birds to missiles to parcels of air the effect of coriolis force various latitudes we can see that coriolis force maximum at high latitudes minimum at equator we can deduce that a similar pressure gradient geostrophic wind speed will be greater at 30°n than at 60°n.



For the same pressure gradient at 60°N 50°N and 40°N the speed of the geostrophic wind will be ?

exemple reponse 240
For same pressure gradient at 60°n 50°n and 40°n speed of geostrophic wind will be Greater at 3 °n than at 6 °n. to have a geostrophic wind we need to have a pressure gradient force coriolis force (create earth's rotation depending on geographic latitude) we need to have two differents air mass to have a pressure gradient force (pgf) since earth rotates objects that are above earth apparently move or are deflected if they are already moving owing to it's rotation this apparent motion caused the coriolis force in northern hemisphere objects will be deflected to their right while in southern hemisphere objects will be deflected to their left the magnitude of deflection also a function of distance from equator velocity so farther from equator object is greater deflection the faster an object moving greater deflection these 'object can be anything from airplanes to birds to missiles to parcels of air the effect of coriolis force various latitudes we can see that coriolis force maximum at high latitudes minimum at equator we can deduce that a similar pressure gradient geostrophic wind speed will be greater at 40°n than at 50°n or 60°n.

Under anticyclone conditions in the northern hemisphere with curved isobars the speed of the gradient wind is ?

exemple reponse 244
Under anticyclone conditions in northern hemisphere with curved isobars speed of gradient wind Greater than geostrophic wind. we have a geostrophic wind when pressure gradient force (pgf) exactly balanced coriolis force it only happens when isobars are straights parallels if isobars are curved an additional force centrifugal force introduced always tries to throw parcel of air outwards from centre of its rotation the resulting movement of air called gradient wind with an area of high pressure (anticyclone) centrifugal force acting in same direction as pgf effectively increasing it coriolis balances total force (pgf + centrifugal force) the gradient wind 'high round a high' (i e a given gap between isobars gradient wind stronger than geostrophic wind) with an area of low pressure (cyclonic system) centrifugal force opposing pgf effectively decreasing it coriolis balances total force (pgf centrifugal force) the gradient wind 'low round a low' (i e a given gap between isobars gradient wind weaker than geostrophic wind).

  • exemple reponse 245
    Considering that portion of route indicated from 30°e to 50°e upper winds in january above fl 300 are most likely to be 321 A subtropical westerly jet stream maximum speed exceeding 9 kt. the subtropical jet stream located around 30°n jet streams vary in height of 20000 ft to 40000 ft can reach speeds of more than 240 kt .

  • exemple reponse 246
    The core of polar front jet stream usually located in Tropical air below tropopause. .

  • exemple reponse 247
    A wind of 20 knots corresponds to an approximate speed of Tropical air below tropopause. 1 kt equal around 0 5 m/s.

  • exemple reponse 248
    After a sunny day followed a long clear night you take off from an airfield at mid latitudes an hour before sunrise the field not situated close to coast though pressure gradient rather large easterly surface wind weak and makes A sudden strong increase in wind speed strong veering of wind a short time after take off. the long clear night will lead to surface temperature inversion (radiation inversion between surface up to 500 ft) strong wind above this layer has a different direction since it not affected surface friction the inversion acts like a boundary between two layers you will have a sudden change in wind speed direction.

  • Question 128-8

    At about what geographical latitude as average assumed the zone of prevailing westerlies A sudden strong increase in wind speed strong veering of wind a short time after take off. westerlies average latitude 50°n (and 50°s south hemisphere).

  • Question 128-9

    At which time if any are polar front jet streams over south pacific usually strongest A sudden strong increase in wind speed strong veering of wind a short time after take off. strongest polar front jet streams are in winter in south pacific (southern hemisphere) winter in july.

  • Question 128-10

    During periods of undisturbed radiation weather overland Surface wind speed tends to be highest during mid afternoon. with undistubed radiation weather ground will get extremely hot (reaching a maximum at about 1400 local time) the heating will increase turbulence that will 'pul more freestream flow down into boundary layer thus increasing surface wind less surface friction at night means none of freestream gets 'pulle down so you will have slower speed at night.

  • Question 128-11

    From summer to winter polar front jet stream over north atlantic moves Towards south the speed increases. with undistubed radiation weather ground will get extremely hot (reaching a maximum at about 1400 local time) the heating will increase turbulence that will 'pul more freestream flow down into boundary layer thus increasing surface wind less surface friction at night means none of freestream gets 'pulle down so you will have slower speed at night.

  • Question 128-12

    In relation to polar front jet stream greatest rate of wind shear most likely to occur Close to core on polar side. the greatest rate of wind shear most likely to occur close to core on polar side it in warm (tropical) air but on cold air side of core.

  • Question 128-13

    In summer in northern hemisphere maximum wind speeds associated with sub tropical jet streams are usually located Below tropopause at about 2 hpa. the polar front sub tropical equatorial jet streams are all just below tropopause the sub tropical jetstream at about fl390 in summer (200 hpa) the highest wind speed in core.

  • Question 128-14

    Isotachs are lines joining equal Below tropopause at about 2 hpa. the polar front sub tropical equatorial jet streams are all just below tropopause the sub tropical jetstream at about fl390 in summer (200 hpa) the highest wind speed in core.

  • Question 128-15

    Maximum wind speeds associated with subtropical jet streams are usually located in Tropical air below tropopause. the subtropical jet stream located around 30°n/s jet streams vary in height from 20000 ft (close to poles) to 40000 ft (at 30°n/s) can reach speeds of more than 240 kt it in warm tropical air below tropopause that maximum wind speeds can be recorded.

  • Question 128-16

    Sea breezes are most likely to occur when Slack pressure gradient clear skies result in relatively high land temperatures. sea breeze circulations most often occur on warm sunny days during spring summer when temperature of land normally higher than temperature of water slack pressure gradient means that we are in an area with light or no wind (due to difference of pressure gradient between an anticyclone or a low).

  • Question 128-17

    The length width and depth of a typical mid latitude jet stream are respectively mn 5 mn ft. sea breeze circulations most often occur on warm sunny days during spring summer when temperature of land normally higher than temperature of water slack pressure gradient means that we are in an area with light or no wind (due to difference of pressure gradient between an anticyclone or a low).

  • Question 128-18

    The most likely place to encounter clear air turbulence associated with a jet stream Close to core on side facing polar air. the strongest cat in warm tropical air but on cold polar air side of core.

  • Question 128-19

    What surface wind forecast 2200 utc eddf 272200z 280624 vrb05kt 4000 br sct005 ovc013 becmg 1314 9000 shra ovc015 prob40 tempo 1416 vrb15g25kt 1600 tsra ovc010cb becmg 1618 26010kt bkn030 becmg 2122 cavok Close to core on side facing polar air. eddf 272200z forecast prepared on twenty seventh day of month at 22h00 utc 280624 vrb05kt 4000 br sct005 ovc013 becmg 1314 9000 shra ovc015 prob40 tempo 1416 vrb15g25kt 1600 tsra ovc010cb becmg 1618 26010kt the time period when change expected the gradual change will occur at an unspecified time within this time period the wind will change remain unchanged until end of taf (cavok does not change wind) bkn030 becmg 2122 cavok.

  • Question 128-20

    What surface wind forecast eta 1700 utc at kingston mkjp 160430z 160606 36010kt 9999 few025cb becmg1315 14020g34kt few015cb sct025 prob30 tempo 1720 6000 +shra sct010 bkn015cb becmg 2301 34010kt few025= 4 ° / 2 kt gusts 34 kt. becmg (becoming) indicates a change to forecast conditions expected to occur slowly within period designated in time group immediately following heading the duration of this change normally about 2 hours the elements included in becmg line will supercede some of previous taf groups but it possible all groups may change any group omitted in becmg line will be same during becmg period as indicated in main taf line in this question wind becoming 140°/20 kt gusts 34 kt (14020g34kt) between 13h 15h it will remain unchanged until 23h then wind becoming 340°/10kt between 23h 01h.

  • Question 128-21

    When and where an easterly jet stream likely to be encountered In summer from south east asia extending over southern india to central africa. this jet occurs in northern summer between 10°n 20°n chiefly over or just to south of high land masses such as in asia africa its occurrence due to a temperature gradient with colder air to south which produces sufficient temperature differential above 45000 ft to give wind speeds of over 100 kt because colder temperatures at height are to south it an easterly jet this jet now more usually known as tropical easterly jet perhaps more correctly as it lies some distance from equator .

  • Question 128-22

    When compared to geostrophic wind in northern hemisphere surface friction will cause surface wind to In summer from south east asia extending over southern india to central africa. at low elevations friction will slow air hence coriolis force will be less effective in its deflection of wind as elevation decreases direction backs (changes direction in an counter clockwise motion) in northern hemisphere at mid latitude over land wind speed in friction layer decrease 50% angle between wind direction isobars changes 30° (value to be used in examinations).

  • Question 128-23

    Which area of a polar front jet stream in northern hemisphere has highest probability of turbulence Looking downstream area to left of core. the jet always below tropopause the strongest turbulence in warm tropical air but on cold polar air side of core (looking downstream area to left of core).

  • Question 128-24

    Which of following statements concerning variation in wind speed between summer and winter on north atlantic between fl 300 and fl 400 most correct the average westerly component Is greater in winter. the polar front jet on north atlantic moves south increases speed in winter then moves north decreases speed in summer.

  • Question 128-25

    Which of following types of jet streams can be observed all year round Subtropical jet stream polar front jet stream. polar front jet stream subtropical jet stream can be observed all along year.

  • Question 128-26

    Where as a general rule the core of polar front jet stream to be found In tropical air mass. the polar jet stream always below tropopause in warm tropical air mass.

  • Question 128-27

    Where the projection of polar front jet stream on surface most likely to be found in relation to cold and warm fronts of a depression 5 to 2 nm behind cold front 3 to 45 nm ahead of warm front. a cold front has an inclined plane of 1/50 a warm front an inclined plane of 1/150 the projection of polar front jet stream on surface which most likely to be found in relation to cold warm fronts of a depression will be located closer behind cold front far behind warm front.

  • Question 128-28

    Which statement correct the southern hemisphere In friction layer wind backs with increasing height. a cold front has an inclined plane of 1/50 a warm front an inclined plane of 1/150 the projection of polar front jet stream on surface which most likely to be found in relation to cold warm fronts of a depression will be located closer behind cold front far behind warm front.

  • Question 128-29

    What the best approximation the wind speed at flight level 250 By interpolation of wind information available from 5 3 hpa charts while also considering maximum wind information found on significant weather chart. a cold front has an inclined plane of 1/50 a warm front an inclined plane of 1/150 the projection of polar front jet stream on surface which most likely to be found in relation to cold warm fronts of a depression will be located closer behind cold front far behind warm front.

  • Question 128-30

    What the average wind forecast fl 300 between edinburgh and madrid 340 By interpolation of wind information available from 5 3 hpa charts while also considering maximum wind information found on significant weather chart. from edinburgh to madrid above england almost no wind over manche wind from 280° 30 kt above atlantique wind from 280° 45 to 50 kt above spain wind from 280° 35 kt average forecast wind 280°/30kt.

  • Question 128-31

    At 40°n 20°w forecast wind at fl 390 345 By interpolation of wind information available from 5 3 hpa charts while also considering maximum wind information found on significant weather chart. pennants correspond to 50 kt feathers correspond to 10 kt half feathers correspond to 5 kt 4 feathers + 1 half feather = 45 kt.

  • Question 128-32

    What characteristics will surface winds have in an area where isobars on weather map are very close together Strong flowing somewhat across isobars. when isobars are close together pressure gradient force greater wind velocities are stronger the wind will be parallel to isobars but surface friction will make wind direction change to flow at an angle to isobars.

  • Question 128-33

    What necessary the development of a polar front jet stream Strong horizontal temperature gradients. the horizontal temperature gradient essential the formation of thermal wind.

  • Question 128-34

    The average forecast wind the leg from madrid to dhahran at fl 390 361 Strong horizontal temperature gradients. (45 + 40 + 30 + 45 + 40 + 45 + 50 + 50 + 50 + 65 + 65 + 45) / 12 = 47 5 kt.

  • Question 128-35

    In mid latitudes of northern hemisphere wind blows Clockwise around anticyclones anti clockwise around cyclones. (45 + 40 + 30 + 45 + 40 + 45 + 50 + 50 + 50 + 65 + 65 + 45) / 12 = 47 5 kt.

  • Question 128-36

    In northern hemisphere with an anticyclonic pressure system geostrophic wind at 2000 ft over sea 060°/15kt at same position surface wind most likely to be Clockwise around anticyclones anti clockwise around cyclones. values to be used in examinations over sea wind speed in friction layer decrease 30% wind in friction layer blows across isobars towards low pressure angle between wind direction isobars changes 10° over land wind speed in friction layer decrease 50% wind in friction layer blows across isobars towards low pressure angle between wind direction isobars changes 30° the wind blows parallel to isobars in northern hemisphere surface wind will back slowdown compared to it.

  • Question 128-37

    At which height and at what time of year can an aircraft be affected the equatorial jet stream Fl 5 from june to august. the equatorial jet located between 5° 15°n it a seasonal zonal wind it generated the high thermal gradients barometrics between equator asia by latent heat released above indian sub continent (humid monsoon begins in june) it located around an axis tibet senegal in summer the tropopause lower warmer above poles higher colder at equator equatorial tropopause around 14 to 16 km in summer the equatorial jet located just below equatorial tropopause.

  • Question 128-38

    According to extract of surface isobar map surface wind direction over sea approximately 365 Fl 5 from june to august. in northern hemisphere if you stand with your back to wind low pressure on your left (buys ballot's law) we are in southern hemispere situtation reversed if you stand with your back to wind low pressure on your right so wind blows parallel to isobars from 130° over sea wind speed in friction layer decrease 30% wind in friction layer blows across isobars towards low pressure angle between wind direction isobars changes 10° so answer 140°.

  • Question 128-39

    In appendix are shown four sections of 700 hpa wind chart the diagram representing most accurately wind direction and speed 366 3 °/3 kt (diagram a). if you stand with your back to wind in northern hemisphere low pressure on your left (buys ballot's law) in southern hemisphere if you stand with your back to wind low pressure on your right as in diagrams a c on upper wind charts 'feather on wind arrows are on low pressure/low isohypse side of arrow which only correctly shown in diagram a.

  • Question 128-40

    At fl 300 between geneva and tunis what mean wind would be most likely 367 3 °/3 kt (diagram a). wind direction from (230+240+250+260)/4 = 245° wind speed is (60+35+45+55)/4 = 48 75 kt.


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