EASA ATPL METEROLOGY EXAM -

EASA ATPL METEROLOGY EXAM -

300 QUESTIONS AND CORRECT DET AILED ANSWERS

(VERIFIED ANSWERS ) |AGRADE

Severe CAT likely to occur when: - ANSWER- wind in jet core > 110

kts

vertical shear > 5 kts / 1000 ft

horizontal shear > 45 kts / 150 NM

„where would you expect to encounter the greatest intensity of CAT associated with polar jet stream?" - ANSWER- along the axis of the jet stream core to the left (looking downstream)

aka on the depression side

„CAT should be anticipated when: - ANSWER- a sharp trough area aloft

is present, even though the wind speeds may be considerably less than that of jet stream winds"

Mountain Waves

favorable conditions: - ANSWER- 1) wind speed > 20 kts at top of mtn

2) wind blows at right angles to mtn range (or within 30° of this)

3) wind speed increases with altitude, but wind direction remains more or less constant (strong waves are often associated with jet streams)

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4) atmosphere stable (preferably stratified in several thin stable layers) and especially if there is an inversion or isothermal present just above the level of the mountain top, with less stable air above and below, between crest level and a few thousand feet above

Rotor - ANSWER- - occur in lower turbulent zone that stretches from surface downwind of the mountain and up to a height of about 1000- 2000ft above mountain top

• usually first rotor (situated below and generated by first wave) that is

most intense with severe to extreme turbulence

• rotor zone center is situated at about same height as mountain top

• if closed circulation is present this will usually show up as a wind

reversal at the surface compared to the wind at height

• rotor cloud (aka roll cloud) at top o frotor zone often indicates presence

of a rotor phenomena

• looks like a line of small cumulus clouds close together or sometimes

stratus fractus

in arid areas without sufficient moisture for a rotor cloud to form, a dust or sand might whirl up on the upwind side of the rotor zone (closest to the mtn)

• severe turb -> avoid!

lenticular clouds - ANSWER- stationary and may appear at several levels

• form within stable layers in the crests of mountain waves
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• usually appear up to a few thousand feet above mountain crests but can

also be seen at any level up to the tropopause, sometimes even above

• airflow through these clouds usually smooth

(unless edges of lenticular clouds appear ragged, indication of moderate to strong turbulence)

cap clouds - ANSWER- ascending motion on upward / windward side of mountain and pressure falls around the top and the lee side of the mountain intensifies condensation and a cloud cap, hiding the top of the elevated terrain

• appears over crest of mountain ridge

• typically form on upwind side of mountain ridge

• strong surface winds can sometimes extend the cap cloud a little bit

further beyond the mountain top over to the downwind (lee-) side of mountain

this overhang is a good indication of a strong "föhn" wind

if you see a cap cloud on the upwind side of a mountain, the cloud itself is typically quite harmless, but indication that there is a great possibility of other, more dangerous mountain wave phenomena (rotor zone, strong down-draughts as great as 5000 fpm etc) present on the downwind side

mountain wind / katabatic - ANSWER- down, mountain, night, cooling

valley wind / anabatic - ANSWER- up from valley, day, warming -> Anabatic (arrow upwards)

jet stream ratio - ANSWER- 1:100

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temperature relation crossing W-E Jetstream from S-N - ANSWER- below JS core altitude -> temp falls at JS core altitude -> temp constant above JS core altitude -> temp rises

*Remember* colder air to left looking downwind => below tropopause => wind speed increases with height

colder air to right looking downwind => above tropopause => wind speed decreases with height

equatorial jet stream - ANSWER- - occurs in summer between JUNE and AUGUST as result of monsoon climate

• blowing from SE asia through southern india towards central Africa
• position typically around 15°N
• core altitude typically between FL450-500
• speeds typically up to 60 kts, rarely over 100
• ** only major jet stream that is easterly (E=>W)

facts about typical polar front jet stream - ANSWER- - wind accelerates with increasing alt up to level where temp contrast between air masses is equalized

• at alts above that the wind speed decreases
• steepest pressure surface slope will be at the level where the temp is

the same on both sides of the frontal surface

• normally at strongest in area between a trough and ridge
• STRONGEST IN WINTER (south pacific = winter in July)

max wind speed of polar front jet stream found ... - ANSWER- on warm side of frontal zone at altitudes just above the tropopause of the cold air (about 1000-5000 ft below the warm tropopause)

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