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Preparation > civilian : If paris reports a wind of 30012kt on the metar what wind velocity would you ?

Question 129-1 : 33025kt 23030kt 30025kt 27020kt

. values to be used in examinations .over sea wind speed in friction layer decrease by 30% the wind in the friction layer blows across the isobars towards the low pressure angle between wind direction and isobars changes by 10°..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° exemple 229 33025kt33025kt

Which of the following is true of a land breeze ?

Question 129-2 : It blows from land to water it blows from water to land it blows by day it blows only at noon

.land breeze during the night land is cold sea is warm . 600.during the day the situation reverses and the wind will blow from the sea sea breeze . 601 exemple 233 it blows from land to water.it blows from land to water.

An aircraft is approaching under visual flight rules an airfield whose runway ?

Question 129-3 : Crosswind from the right crosswind from the left tailwind headwind

.during a sunny afternoon sea breeze is likely to occur . 601.if the coast and runway are aligned east/west a right hand circuit would mean runway 27 in use sea to the north and land to the south .at touch down the northerly sea breeze would be from the right exemple 237 crosswind from the right.crosswind from the right.

An aircraft is approaching under visual flight rules an airfield northern ?

Question 129-4 : Crosswind from the left headwind tailwind crosswind from the right

.during a sunny afternoon sea breeze is likely to occur . 601.we should expect a crossing from the left on final approach and landing . 544

When will the surface wind in a metar record a gust factor ?

Question 129-5 : When gusts are at least 10 knots above the mean wind speed when gusts are at least 15 knots above the mean wind speed with gusts of at least 25 knots with gusts of at least 35 knots

exemple 245 when gusts are at least 10 knots above the mean wind speed.when gusts are at least 10 knots above the mean wind speed.

Select from the map the average wind for the route zurich rome at fl110 . 303 ?

Question 129-6 : 230/10 200/30 040/10 250/20

. 548.a feather corresponds to 10 kt .if you look at the wind close to rome it comes approximately from 235° .average wind is 230°/10 kt

Select from the map the average wind for the route athens geneva at fl 160 . ?

Question 129-7 : 240/40 210/25 260/40 050/35

.on the chart we find an average wind of 245° ==> 240+235+245+255 /4.this chart is for flight level 180 and they ask the average wind at fl160 thus the wind will be less than 245° northern hemisphere.we find a wind speed of 46 25 kt wind force will also be less only one answer remains correct 240/40 . 484 exemple 253 240/40.240/40.

Select from the map the average wind for the route zurich hamburg at fl 240 . ?

Question 129-8 : 230/20 020/20 200/15 260/25

.on the left of zurich we notice a wind of 200°/20 kt .on the right of zurich the wind is from 250°/25 kt .the average wind will be 230°/20 kt exemple 257 230/20.230/20.

Select from the map the average wind for the route shannon lisboa at fl 290 . ?

Question 129-9 : 360/80 030/70 190/75 340/90

. 551.the wind comes clearly from the north at a speed of . 70 + 90 + 90 + 85 + 80 /5 = 83 kt .the map is for fl300 the speed at fl290 will be slower than 83 kt exemple 261 360/80.360/80.

When otherwise calm and clear conditions exist a station on the shore of a ?

Question 129-10 : From the water in daytime and from the land at night continually from land to water continually from water to the land from the land in daytime and from the water at night

.land breeze during the night land is cold sea is warm . 600.during the day the situation reverses and the wind will blow from the sea sea breeze . 601 exemple 265 from the water in daytime and from the land at night.from the water in daytime and from the land at night.

The greater the pressure gradient the ?

Question 129-11 : Closer the isobars and the stronger the wind further the isobars will be apart and the weaker the wind closer the isobars and the lower the temperatures further the isobars will be apart and the higher the temperature

exemple 269 closer the isobars and the stronger the wind.closer the isobars and the stronger the wind.

When isobars for an area in the mid latitudes on a weather map are close ?

Question 129-12 : Strong changing direction rapidly blowing perpendicular to the isobars light

exemple 273 strong.strong.

In the northern hemisphere a pilot flying at 1000 ft above ground level ?

Question 129-13 : Left and behind right and behind about 45 degrees to the right of directly ahead directly ahead

.in northern hemisphere wind flows counter clockwise around a low . 573.the wind blowing from left and behind exemple 277 left and behind.left and behind.

In the northern hemisphere the wind at the surface blows ?

Question 129-14 : Counter clockwise around and toward the centre of a low pressure area from a low pressure area to a high pressure area clockwise around and away from the centre of a low pressure area counter clockwise around and away from the centre of a high pressure area

.in the northern hemisphere the wind is counter clockwise around low pressure and the effect of surface friction will make the wind 'back and slack' in the northern hemisphere exemple 281 counter-clockwise around, and toward the centre of, a low pressure areacounter-clockwise around, and toward the centre of, a low pressure area

Wind is caused by ?

Question 129-15 : Horizontal pressure differences the rotation of the earth friction between the air and the ground the movements of fronts

exemple 285 horizontal pressure differenceshorizontal pressure differences

During a descent from 2000 ft above the surface to the surface no frontal ?

Question 129-16 : Backs and decreases veers and increases backs and increases veers and decreases

.at low elevations friction will slow the air and hence the coriolis force will be less effective in its deflection of the wind . 561.when entering in the friction layer at about 2000 ft above the surface 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 289 backs and decreases.backs and decreases.

The foehn wind is a ?

Question 129-17 : Warm katabatic wind cold katabatic wind warm anabatic wind cold anabatic wind

.katabatic wind from the greek katabaino to go down is the generic term for downslope winds flowing from high elevations of mountains plateaus and hills down their slopes to the valleys or planes below katabatic winds exist in many parts of the world and there are many different names for katabatic winds depending where they are located and how they are formed .warm dry katabatic winds occur on the lee side of a mountain range situated in the path of a depression examples for these descending adiabatically warmed katabatic winds are the foehn winds exemple 293 warm katabatic wind.warm katabatic wind.

The sea breeze is a wind from the sea ?

Question 129-18 : Occurring only in the lower layers of the atmosphere in daytime that reaches up to the tropopause in daytime blowing at night in mid latitudes occurring only in mid latitudes and in daytime

exemple 297 occurring only in the lower layers of the atmosphere in daytimeoccurring only in the lower layers of the atmosphere in daytime

Geostrophic wind is the wind when isobars are ?

Question 129-19 : Straight lines and no friction is involved curved lines and no friction is involved straight lines and friction is involved curved lines and friction is involved

.we have a geostrophic wind when the pressure gradient force pgf is exactly balanced by coriolis force . 582.it is only happens when isobars are straights and parallels.if the isobars are curved an additional force centrifugal force is introduced and always tries to throw the parcel of air outwards from the centre of its rotation and the resulting movement of air is called the gradient wind . 583.with an area of high pressure anticyclone the centrifugal force is acting in the same direction as pgf effectively increasing it coriolis balances the total force pgf + centrifugal force and the gradient wind is 'high round a high' i e for a given gap between the isobars the gradient wind is stronger than the geostrophic wind.with an area of low pressure cyclonic system the centrifugal force is opposing the pgf effectively decreasing it coriolis balances the total force pgf centrifugal force and the gradient wind is 'low round a low' i e for a given gap between the isobars the gradient wind is weaker than the geostrophic wind exemple 301 straight lines and no friction is involved.straight lines and no friction is involved.

What relationship exists between the wind at 3000 feet and the surface wind ?

Question 129-20 : The wind at 3000 feet is parallel to the isohypses and the surface wind direction is across the isobars toward the low pressure and the surface wind is weaker they have the same direction but the surface wind is weaker caused by friction they are practically the same except when eddies exist caused by obstacles the surface wind is veered compared to the wind at 3000 feet and is usually weaker

exemple 305 the wind at 3000 feet is parallel to the isohypses and the surface wind direction is across the isobars toward the low pressure and the surface wind is weaker.the wind at 3000 feet is parallel to the isohypses and the surface wind direction is across the isobars toward the low pressure and the surface wind is weaker.

The wind tends to follow the contour lines isohypses above the friction layer ?

Question 129-21 : The coriolis force tends to balance with the horizontal pressure gradient force contour lines are lines that connect points with the same wind speed in the upper air the coriolis force acts perpendicular on a line that connects high and low pressure system the friction of the air with the earth's surface gives the airflow a diversion perpendicular to the gradient force

.we have a geostrophic wind when the pressure gradient force pgf is exactly balanced by coriolis force . 582.it is only happens when isobars are straights and parallels.if the isobars are curved an additional force centrifugal force is introduced and always tries to throw the parcel of air outwards from the centre of its rotation and the resulting movement of air is called the gradient wind . 583.with an area of high pressure anticyclone the centrifugal force is acting in the same direction as pgf effectively increasing it coriolis balances the total force pgf + centrifugal force and the gradient wind is 'high round a high' i e for a given gap between the isobars the gradient wind is stronger than the geostrophic wind.with an area of low pressure cyclonic system the centrifugal force is opposing the pgf effectively decreasing it coriolis balances the total force pgf centrifugal force and the gradient wind is 'low round a low' i e for a given gap between the isobars the gradient wind is weaker than the geostrophic wind exemple 309 the coriolis force tends to balance with the horizontal pressure gradient force.the coriolis force tends to balance with the horizontal pressure gradient force.

The wind speed in a system with curved isobars compared to a system with ?

Question 129-22 : Higher if curvature is anticyclonic always higher always lower higher if curvature is cyclonic

.we have a geostrophic wind when the pressure gradient force pgf is exactly balanced by coriolis force . 582.it is only happens when isobars are straights and parallels.if the isobars are curved an additional force centrifugal force is introduced and always tries to throw the parcel of air outwards from the centre of its rotation and the resulting movement of air is called the gradient wind . 583.with an area of high pressure anticyclone the centrifugal force is acting in the same direction as pgf effectively increasing it coriolis balances the total force pgf + centrifugal force and the gradient wind is 'high round a high' i e for a given gap between the isobars the gradient wind is stronger than the geostrophic wind.with an area of low pressure cyclonic system the centrifugal force is opposing the pgf effectively decreasing it coriolis balances the total force pgf centrifugal force and the gradient wind is 'low round a low' i e for a given gap between the isobars the gradient wind is weaker than the geostrophic wind exemple 313 higher if curvature is anticyclonic.higher if curvature is anticyclonic.

The geostrophic wind depends on ?

Question 129-23 : Density earth's rotation geographic latitude earth's rotation geographic latitude centripetal force geographic latitude centripetal force height centripetal force height pressure gradient

.to have a geostrophic wind we need to have a pressure gradient force create by density and coriolis force create by earth's rotation and depending on geographic latitude.why density we need to have two differents air mass to have a pressure gradient force pgf . 564.why earth's rotation and geographic latitude since the earth rotates objects that are above the earth apparently move or are deflected if they are already moving owing to it's rotation this apparent motion is caused by the coriolis force .in the northern hemisphere objects will be deflected to their right while in the southern hemisphere objects will be deflected to their left .the magnitude of the deflection is also a function of distance from the equator and velocity so the farther from the equator the object is the greater the deflection and the faster an object is moving the greater the deflection . these 'objects' can be anything from airplanes to birds to missiles to parcels of air . 565.the effect of the coriolis force for various latitudes . 566 exemple 317 density, earth's rotation, geographic latitude.density, earth's rotation, geographic latitude.

In a mountain valley wind circulation the mountain wind blows ?

Question 129-24 : At night down from the mountains at night up from the valley during the day down from the mountains during the day up from the valley

.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 321 at night down from the mountains.at night down from the mountains.

Ahead of a warm front in northern hemisphere the wind direction changes from ?

Question 129-25 : Veers in the friction layer and veers above the friction layer backs in the friction layer and veers above the friction layer veers in the friction layer and backs above the friction layer backs in the friction layer and backs above the friction layer

. 567.ahead of a warm front in northern hemisphere as ahead of a cold front the wind veers in the friction layer and veers above the friction layer .we know that the wind turns counterclockwise around a low pressure but for an observer on the ground looking at the front the wind veers turn clockwise at his position exemple 325 veers in the friction layer and veers above the friction layer.veers in the friction layer and veers above the friction layer.

The difference between geostrophic wind and gradient wind is caused by ?

Question 129-26 : Curvature of isobars friction horizontal temperature gradients slope of pressure surfaces

.we have a geostrophic wind when the pressure gradient force pgf is exactly balanced by coriolis force . 582.it is only happens when isobars are straights and parallels.if the isobars are curved an additional force centrifugal force is introduced and always tries to throw the parcel of air outwards from the centre of its rotation and the resulting movement of air is called the gradient wind . 583.with an area of high pressure anticyclone the centrifugal force is acting in the same direction as pgf effectively increasing it coriolis balances the total force pgf + centrifugal force and the gradient wind is 'high round a high' i e for a given gap between the isobars the gradient wind is stronger than the geostrophic wind.with an area of low pressure cyclonic system the centrifugal force is opposing the pgf effectively decreasing it coriolis balances the total force pgf centrifugal force and the gradient wind is 'low round a low' i e for a given gap between the isobars the gradient wind is weaker than the geostrophic wind exemple 329 curvature of isobars.curvature of isobars.

During periods of prolonged clear skies associated with anticyclonic conditions ?

Question 129-27 : Surface wind speed tends to be highest during the early afternoon surface wind speed tends to be highest at night angle between isobars and surface wind direction tends to be greatest in the early afternoon wind tends to back from early morning until early afternoon

.anticyclonic conditions indicate a high pressure system is present .with a high pressure system and clear skies present we expect higher temperatures and these are at their highest during the afternoon .as the temperature near the surface increases the air density decreases and so the effect of surface friction is lessened and wind speed is allowed to pick up exemple 333 surface wind speed tends to be highest during the early afternoon.surface wind speed tends to be highest during the early afternoon.

The geostrophic wind speed is directly proportional to the ?

Question 129-28 : Horizontal pressure gradient curvature of isobars sine of latitude density of the air

.the speed of a geostrophic wind calculated from the pressure gradient air density rotational velocity of the earth and latitude the calculation ignores the curvature of the wind's path a geostrophic wind is proportional to the pressure gradient or inversely proportional to the distance between the isobars . 568.winds exist because of horizontal and vertical pressure gradient so atmospheric motion can be deduced from isobaric surface charts etc if the horizontal pressure gradient force is exactly balanced in magnitude by coriolis effect accelerations of the air will be relatively small and a geostrophic wind will flow horizontally at a constant speed proportional to the isobaric spacing gradient perpendicular to the two opposing forces and parallel to straight isobars thus geostrophic wind speed is proportional to the pressure gradient the closer the isobars the higher will be geostrophic wind speed exemple 337 horizontal pressure gradient.horizontal pressure gradient.

A strong dry and warm downslope wind produced by prior enforced ascent of air ?

Question 129-29 : Foehn scirocco mistral bora

exemple 341 foehn.foehn.

Geostrophic wind ?

Question 129-30 : Is perpendicular to the horizontal pressure gradient force is directly proportional to the density of the air always increases with increasing height veers with height if cold air is advected in the northern hemisphere

.we have a geostrophic wind when the pressure gradient force pgf is exactly balanced by coriolis force . 582.it is only happens when isobars are straights and parallels .the geostrophic wind yellow arrow is perpendicular to the horizontal pressure gradient force pgf and to the coriolis force exemple 345 is perpendicular to the horizontal pressure gradient force.is perpendicular to the horizontal pressure gradient force.

Which of the following statements concerning jet streams is correct ?

Question 129-31 : In the northern hemisphere both westerly and easterly jet streams occur in the northern hemisphere only westerly jet streams occur in the southern hemisphere no jet streams occur in the southern hemisphere only easterly jet streams occur

.in the northern hemisphere both westerly and easterly jet streams occur . 533.the tropical easterly jet stream blows only during summer from south east asia extending over southern india to central africa exemple 349 in the northern hemisphere both westerly and easterly jet streams occur.in the northern hemisphere both westerly and easterly jet streams occur.

Under which of the following conditions is the most severe cat likely to be ?

Question 129-32 : A curved jet stream near a deep trough a jet stream with great spacing between the isotherms a westerly jet stream at low latitudes in the summer a straight jet stream near a low pressure area

. 572.a curving jet stream associated with a deep low pressure trough can be expected to cause great turbulence exemple 353 a curved jet stream near a deep trough.a curved jet stream near a deep trough.

Above and below a low level inversion the wind is likely to ?

Question 129-33 : Change significantly in speed and direction change in speed but not in direction change in direction but not in speed experience little or no change in speed and direction

.a low level inversion means that a temperature inversion forms near the surface the airstream flowing over ground or water produces a turbulent layer the friction layer up to 500 feet deep in light winds or 3000 feet plus in strong winds .the wind above the inversion often increases because it is insulated from the frictional influence of the surface . 574.above and below a low level inversion the wind is likely to change significantly in speed and direction exemple 357 change significantly in speed and direction.change significantly in speed and direction.

Which of the following statements concerning the core of a polar front jet ?

Question 129-34 : It lies at a height where there is no horizontal temperature gradient the slope of the pressure surfaces at the height of the core is at its maximum it and its surface projection lie in the warm air it lies in the warm air its pressure surfaces are horizontal at the height of the core it lies in the cold air the wind reverses direction at the height of the core

. 637.the polar front jet core is in the warm air but above the cold air tropopause at a point where the temperature in the warm air troposphere is the same as the cold air stratosphere if the cold tropopause is 40°c then above that point in the cold sector the temperature is constant in the warm air at the same level as the cold tropopause the temperature will be warmer say 34°c but will decrease with altitude.at the point where the temperature in the warm air is the same as the 40°c in the cold air stratosphere you will find the strongest wind speed exemple 361 it lies at a height where there is no horizontal temperature gradient, the slope of the pressure surfaces at the height of the core is at its maximum.it lies at a height where there is no horizontal temperature gradient, the slope of the pressure surfaces at the height of the core is at its maximum.

On a particular day part of a polar front jet stream runs from north to south ?

Question 129-35 : The polar air is below and to the east of the core of the jet the polar air is on the eastern side and above the core of the jet below the core of the jet the horizontal temperature gradient runs from north to south above the core of the jet the horizontal temperature gradient runs from north to south

.normaly 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.now let's assume the direction is north to south polar front jet remains in warm air above the cold air .the polar air remains below and to the east of the core of the jet exemple 365 the polar air is below and to the east of the core of the jet.the polar air is below and to the east of the core of the jet.

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

Question 129-36 : Greater at 30°n than at 60°n greater at 60°n than at 30°n the same at all latitudes north or south of 15° equivalent to gradient wind ± thermal component

.to have a geostrophic wind we need to have a pressure gradient force and coriolis force create by earth's rotation and depending on geographic latitude.we need to have two differents air mass to have a pressure gradient force pgf . 564.since the earth rotates objects that are above the earth apparently move or are deflected if they are already moving owing to it's rotation this apparent motion is caused by the coriolis force .in the northern hemisphere objects will be deflected to their right while in the southern hemisphere objects will be deflected to their left .the magnitude of the deflection is also a function of distance from the equator and velocity so the farther from the equator the object is the greater the deflection and the faster an object is moving the greater the deflection .these 'objects' can be anything from airplanes to birds to missiles to parcels of air . 565.the effect of the coriolis force for various latitudes . 566.we can see that coriolis force is maximum at high latitudes and minimum at the equator .we can deduce that for a similar pressure gradient the geostrophic wind speed will be greater at 30°n than at 60°n exemple 369 greater at 30°n than at 60°n.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 ?

Question 129-37 : Greatest at 40°n the same at all latitudes greatest at 60°n least at 50°n

.to have a geostrophic wind we need to have a pressure gradient force and coriolis force create by earth's rotation and depending on geographic latitude.we need to have two differents air mass to have a pressure gradient force pgf . 564.since the earth rotates objects that are above the earth apparently move or are deflected if they are already moving owing to it's rotation this apparent motion is caused by the coriolis force .in the northern hemisphere objects will be deflected to their right while in the southern hemisphere objects will be deflected to their left .the magnitude of the deflection is also a function of distance from the equator and velocity so the farther from the equator the object is the greater the deflection and the faster an object is moving the greater the deflection .these 'objects' can be anything from airplanes to birds to missiles to parcels of air . 565.the effect of the coriolis force for various latitudes . 566.we can see that coriolis force is maximum at high latitudes and minimum at the equator .we can deduce that for a similar pressure gradient the geostrophic wind speed will be greater at 40°n than at 50°n or 60°n exemple 373 greatest at 40°n.greatest at 40°n.

Under anticyclone conditions in the northern hemisphere with curved isobars the ?

Question 129-38 : Greater than the geostrophic wind less than the geostrophic wind the same as the thermal component proportional only to the coriolis force

.we have a geostrophic wind when the pressure gradient force pgf is exactly balanced by coriolis force . 582.it is only happens when isobars are straights and parallels.if the isobars are curved an additional force centrifugal force is introduced and always tries to throw the parcel of air outwards from the centre of its rotation and the resulting movement of air is called the gradient wind . 583.with an area of high pressure anticyclone the centrifugal force is acting in the same direction as pgf effectively increasing it coriolis balances the total force pgf + centrifugal force and the gradient wind is 'high round a high' i e for a given gap between the isobars the gradient wind is stronger than the geostrophic wind.with an area of low pressure cyclonic system the centrifugal force is opposing the pgf effectively decreasing it coriolis balances the total force pgf centrifugal force and the gradient wind is 'low round a low' i e for a given gap between the isobars the gradient wind is weaker than the geostrophic wind exemple 377 greater than the geostrophic wind.greater than the geostrophic wind.

Considering that portion of the route indicated from 30°e to 50°e the upper ?

Question 129-39 : A subtropical westerly jet stream maximum speed exceeding 90 kt a westerly polar front jet stream maximum speed exceeding 90 kt variable in direction and less than 30 kt light easterlies

. 589.the subtropical jet stream is located around 30°n jet streams vary in height of 20000 ft to 40000 ft and can reach speeds of more than 240 kt . 590 exemple 381 a subtropical westerly jet stream, maximum speed exceeding 90 kt.a subtropical westerly jet stream, maximum speed exceeding 90 kt.

The core of the polar front jet stream is usually located in the ?

Question 129-40 : Tropical air below the tropopause polar air above the tropopause polar air below the tropopause tropical air above the tropical tropopause

. 595 exemple 385 tropical air below the tropopause.tropical air below the tropopause.

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