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Question 143-1 : What prevents air from flowing directly from high pressure areas to low pressure areas ? [ Certification weather ]

Coriolis force

Admin .pressure gradient tries to move air from high pressure to low pressure but coriolis force deflects it to the right in the northern hemisphere and to the left in the southern hemisphere

Question 143-2 : What is the approximate speed of a 25 knot wind expressed in kilometres per hour ?

45 km/h

Admin .1 kt = 1 852 km/h.use this formula 25 kt x 2 10% = 45 km/h exemple 247 45 km/h.

Question 143-3 : What is the approximate speed of a 90 km/h wind expressed in knots ?

50 kt

Admin .1 kt = 1 852 km/h.use this formula 90 km/h + 10% /2 = 49 5 kt exemple 251 50 kt.

Question 143-4 : What is the approximate speed of a 40 knot wind expressed in m/sec ?

20 m/sec

Admin .1 kt equal around 0 5 m/s exemple 255 20 m/sec.

Question 143-5 : Where in central europe are the highest wind speeds to be found ?

Just below the tropopause

Admin .the strongest winds in this area are the polar front jetstreams which are just below the warm air tropopause exemple 259 Just below the tropopause.

Question 143-6 : If paris reports a wind of 19015kt on the metar what wind velocity would you expect to encounter at a height of 2000 feet above the ground ?

22030 kt

Admin . 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 263 22030 kt

Question 143-7 : If paris reports a wind of 08010kt on the metar what wind velocity would you expect to encounter at a height of 2000 feet above the ground ?

11020kt

Admin . 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 267 11020kt

Question 143-8 : If paris reports a wind of 16020kt on the metar what wind velocity would you expect to encounter at a height of 2000 feet above the ground ?

19040kt

Admin . 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 271 19040kt

Question 143-9 : If paris reports a wind of 30012kt on the metar what wind velocity would you expect to encounter at a height of 2000 feet above the ground ?

33025kt

Admin . 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 275 33025kt

Question 143-10 : Which of the following is true of a land breeze ?

It blows from land to water

Admin .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 279 It blows from land to water.

Question 143-11 : An aircraft is approaching under visual flight rules an airfield whose runway is parallel to the coast when downwind over the sea the airfield is on the right what wind effect should be anticipated on final approach and landing during a sunny afternoon ?

Crosswind from the right

Admin .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 283 Crosswind from the right.

Question 143-12 : An aircraft is approaching under visual flight rules an airfield northern hemisphere whose runway is parallel to the coast when downwind over the sea the airfield is on the left .what wind effect should be anticipated on final approach and landing during a sunny afternoon ?

Crosswind from the left

Admin .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 exemple 287 Crosswind from the left.

Question 143-13 : When will the surface wind in a metar record a gust factor ?

When gusts are at least 10 knots above the mean wind speed

exemple 291 When gusts are at least 10 knots above the mean wind speed.

Question 143-14 : Select from the map the average wind for the route zurich rome at fl110 . 303 ?

230/10

Admin . 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 exemple 295 230/10.

Question 143-15 : Select from the map the average wind for the route athens geneva at fl 160 . 304 ?

240/40

Admin .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 299 240/40.

Question 143-16 : Select from the map the average wind for the route zurich hamburg at fl 240 . 305 ?

230/20

Admin .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 303 230/20.

Question 143-17 : Select from the map the average wind for the route shannon lisboa at fl 290 . 306 ?

360/80

Admin . 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 307 360/80.

Question 143-18 : When otherwise calm and clear conditions exist a station on the shore of a large body of water will experience wind ?

From the water in daytime and from the land at night

Admin .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 311 From the water in daytime and from the land at night.

Question 143-19 : The greater the pressure gradient the ?

Closer the isobars and the stronger the wind

exemple 315 Closer the isobars and the stronger the wind.

Question 143-20 : When isobars for an area in the mid latitudes on a weather map are close together the wind is most likely to be ?

Strong

exemple 319 Strong.

Question 143-21 : In the northern hemisphere a pilot flying at 1000 ft above ground level directly towards the centre of a low pressure area will find the wind blowing from ?

Left and behind

Admin .in northern hemisphere wind flows counter clockwise around a low . 573.the wind blowing from left and behind exemple 323 Left and behind.

Question 143-22 : In the northern hemisphere the wind at the surface blows ?

Counter clockwise around and toward the centre of a low pressure area

Admin .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 327 Counter-clockwise around, and toward the centre of, a low pressure area

Question 143-23 : Wind is caused by ?

Horizontal pressure differences

exemple 331 Horizontal pressure differences

Question 143-24 : During a descent from 2000 ft above the surface to the surface no frontal passage northern hemisphere the wind normally ?

Backs and decreases

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.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 335 Backs and decreases.

Question 143-25 : The foehn wind is a ?

Warm katabatic wind

Admin .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 339 Warm katabatic wind.

Question 143-26 : The sea breeze is a wind from the sea ?

Occurring only in the lower layers of the atmosphere in daytime

exemple 343 Occurring only in the lower layers of the atmosphere in daytime

Question 143-27 : Geostrophic wind is the wind when isobars are ?

Straight lines and no friction is involved

Admin .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 347 Straight lines and no friction is involved.

Question 143-28 : What relationship exists between the wind at 3000 feet and the surface wind ?

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

exemple 351 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.

Question 143-29 : The wind tends to follow the contour lines isohypses above the friction layer because ?

The coriolis force tends to balance with the horizontal pressure gradient force

Admin .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 355 The coriolis force tends to balance with the horizontal pressure gradient force.

Question 143-30 : The wind speed in a system with curved isobars compared to a system with straight isobars is . other conditions remain the same ?

Higher if curvature is anticyclonic

Admin .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 359 Higher if curvature is anticyclonic.

Question 143-31 : The geostrophic wind depends on ?

Density earth's rotation geographic latitude

Admin .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 363 Density, earth's rotation, geographic latitude.

Question 143-32 : In a mountain valley wind circulation the mountain wind blows ?

At night down from the mountains

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 367 At night down from the mountains.

Question 143-33 : Ahead of a warm front in northern hemisphere the wind direction changes from the surface up to the tropopause .the effect of this change is that the wind ?

Veers in the friction layer and veers above the friction layer

Admin . 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 371 Veers in the friction layer and veers above the friction layer.

Question 143-34 : The difference between geostrophic wind and gradient wind is caused by ?

Curvature of isobars

Admin .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 375 Curvature of isobars.

Question 143-35 : During periods of prolonged clear skies associated with anticyclonic conditions the ?

Surface wind speed tends to be highest during the early afternoon

Admin .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 379 Surface wind speed tends to be highest during the early afternoon.

Question 143-36 : The geostrophic wind speed is directly proportional to the ?

Horizontal pressure gradient

Admin .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 383 Horizontal pressure gradient.

Question 143-37 : A strong dry and warm downslope wind produced by prior enforced ascent of air over hills or mountains is known as a ?

Foehn

exemple 387 Foehn.

Question 143-38 : Geostrophic wind ?

Is perpendicular to the horizontal pressure gradient force

Admin .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 391 Is perpendicular to the horizontal pressure gradient force.

Question 143-39 : Which of the following statements concerning jet streams is correct ?

In the northern hemisphere both westerly and 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 395 In the northern hemisphere both westerly and easterly jet streams occur.

Question 143-40 : Under which of the following conditions is the most severe cat likely to be experienced ?

A curved jet stream near a deep trough

. 572.a curving jet stream associated with a deep low pressure trough can be expected to cause great turbulence exemple 399 A curved jet stream near a deep trough.


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