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7/28/2019 Section 9 TB meteorology
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Sectie9 TB 1
Section 9 FLIGHT HAZARD
1. Icing
2. Turbulence
3. Windshear4. Thunderstorms
5. Hazards in mountainous areas
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Welke Hazards zijn hier eventueel aanwezig?
shear
fog (vis)
Icing
MTI
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1. Icing
loss of performance
large increase in fuel consumption
difficulty with aircraft control
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Conditions for ice accretion
Meteorological factors
Aerodynamic factors
on the ground and during the flight
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Meteorological factors
1. temperature of the outside air in clouds < 0 C
2. supercooled water content of the cloud
3. duration of the flight in the clouds where there is a risk of icing
4. droplet and crystal size distribution*
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droplet and crystal size distribution
Smaller drops easely follow stream lines
Bigger drops dont. (and hit the surface!)*
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The formation of ice accretion in clouds depends on
the quantity and on the size of the supercooled water drops
above the freezing level
the temperature.
the lower the temperature, the smaller the droplet that can
exist in supercooled form
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The supercooled water content depends on the temperature.
Between 0C and -13C *:almost only supercooled water drops (large and small).
Between -13C and -23C:
the large supercooled water drops freeze on ice nuclei(= ice) small supercooled water drops dont. Mix*
Between -23C and -40C:
Only small supercooled water drops can exist
Below -40C
there is no more supercooled water available for ice accretion*
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Aerodynamic factors
speed of the aircraft
the faster the aircraft, the greater the risk of ice deposit*.
temperature of the aircraft's surface
shape (thickness) of the aircraft cell part (wings, antenna,.)
the smaller the curvature, the greater the risk of ice deposit
angle of attack*
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Carburettor icing *
caused by
1. the sudden temperature drop as
latent heat is absorbed when fuel
evaporates
2. due to adiabatic cooling following
the pressure reduction as air is
accelerated through the carburettor
venturi
in cloud or in clear air
most critical range of temperature is from3C and +15C
(warm air can contain more moist)
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The supercooled water drops in different clouds
stratiform cloudsonly light icing between 0C / -13C
Except:
- Sc formed by convetion over sea in winter (Old Sc)
- Sc formed by spreading out of CU below subsidence inversion
- in an active front
- in orographic clouds
cumuliform clouds TCU/CB mod/sev icing between 0C / -23C
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The types of ice accretion
The formation of a deposit of ice on objects:
directly from water vapour, by sublimation* (deposition)
( gas ice)
by the freezing of liquid water drops ( liquid ice)
Types: 1. Clear ice or glaze (IJzel)
2. Rime ice (Ruige Rijp)
3. Mixed ice or cloudy ice (Mixed ijs)
4. Hoar frost (Rijp)
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1. Clear ice or glaze (IJzel*)
Conditions of formation: - large, supercooled water drops (mainlyprecipitation)
- temperatures between FZL* and -18CAspect of clear ice: - transparent, translucent, glassy appearance
- high weight- great adhesion to the frame,
cannot be broken away easily
Formation of clear ice: - CU, CB and NS at temperatures just below
freezing
- in supercooled rain (T < 0C)
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Clear ice
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extremely dangerous form of clear ice occurs in the so-called
ice triangle => rain ice caused by freezing rain
usually ahead of a warm front
sev icing in only a few minutes
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Remarks:
Cold layer at sfc 2 FZLs
(Ice triangle at sfc)
Cold layer 2500` thick
Supercooled drops and/or snow
Becoming warm rain
FZRA
Ca 2000ft
Ca 5000ft
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Main dangers of clear ice
can grow rapidly and it is difficult to remove
if shaken off it flies away in large lumps, which may damage
the surface or may strike the fan and compressor blades
when it occurs on the propeller, may lead to serious vibration.
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Conditions of formation: - small supercooled water dropsCloud drops! (clouds withlow LWC)
- low temperatures (well below 0C)
2. Rime ice (Ruige Rijp)
Aspect of rime ice: - white opaque deposit- little weight
- low density, easy to remove
Formation of rime ice : - in top of CB or in Ns
- in freezing fog (with wind!)
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Sectie9 TB 26
Main dangers of rime ice:
little weight but it alters the aerodynamic characteristics of the
wings and it may block the air intakes.
http://upload.wikimedia.org/wikipedia/commons/9/95/Windbuchencom.jpg7/28/2019 Section 9 TB meteorology
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Sectie9 TB 27
http://upload.wikimedia.org/wikipedia/commons/9/95/Windbuchencom.jpghttp://upload.wikimedia.org/wikipedia/commons/9/95/Windbuchencom.jpg7/28/2019 Section 9 TB meteorology
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Eventueel Weerplaatjes/ sneeuw en rijp dec 2007
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FZFG
FZBR
FZRA
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3. Cloudy ice or mixed ice
mixed ice - formed when supercooled water
droplets are of various sizes or are intermingledwith snow or ice particles.
large range of drop sizes at any temperatures between 0 and -40C
difficult to remove and, because of its roughness, may seriously
increase the drag of the aircraft
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4. Hoar frost (Rijp)
Conditions of formation: - in clear air
- T sfc < frost point of the air
Aspect of hoar frost: - white, crystalline deposit
- little weight
Formation of hoar frost:
by deposition of water vapour directly in ice.
the only icing where no liquid water is involved..!
occurs frequently on parked aircraft during a clear night
when the temperature ofairframe surface falls below 0C*
in flight, if the aircraft moves rapidly into a warmer and
damp layer of air by descent or from ascent into an inversion May occur on bottom sfc of wings holding fuel T
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Main dangers of hoar frost: some loss of radio facilities,
frost on the windscreen before landing.
frost on the airframe may increase the stalling speed.
hoar frost
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Martinair kist op Tunis bij T=28 en Td=22
Rijp?
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Intensity of Icing
Light. ( ) problem if flight is prolonged more than one hour in the
environment, usede-icing/anti-icing equipment
Moderate. ( ) short encounter becomes potentially hazardous
and use of de-icing/anti-icing equipment is
necessary or a diversion is necessary to escape
the icing conditions.
Severe. ( ) rate of accumulation is such that de-icing/anti-icingequipment fails to remove or control the hazard.
Immediate diversion is necessary
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Dangers of aircraft icing
1. Increase in weight2. Loss of lift, deformation of aerodynamic characteristics.
3. Increase in drag. The stall speed of an ice covered aircraft
may be 20 to 30 percent higher than normal.
4. Loss of power, carburettor icing
5. Loss of control, icing on control surface hinges
6. Loss of thrust, propeller icing
7. Loss of vision, windscreen freezing
8. Loss of communication, icing of aerials
9. Pitot tube icing10. Unbalance of aircraft, unbalance of propellers
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Dangerous zones of icing in clouds and fronts
Convective cloudsBetween FZL and -23oC moderate or severe icing - clear ice/ cloudy ice
Between -23oC and -40oC light icing - rime ice
Below -40C small risk of light icing
Non-frontal stratified clouds, St, Sc, Ac
Between FZL and -10oC moderate icing
Below -10oC light icing
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Frontal clouds
Warm front Cold front
non-active 0 to -10C
< -10C
risk of mod icing
risk of light icing
0 to -10C
< -10C
risk of mod icing
risk of light icing
with embd CB
active 0 to -15C
< -15C
risk of mod (sev) icing
risk of light icing
0 to -23C
-23 to -40C
risk of mod to sev icing
risk of light icing
Icing at above 0 C
tanks of an aeroplane on the ground contain fuel that has a
temperature below zero, moisture condensation
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Sectie9 TB 41
Ground de-icing and anti-icing
de-icing:removing ice formations
anti-icing:preventing new accretions from forming
freezing point depressant (FPD) fluids
take care of holdover time*
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Sectie9 TB 43
Recommendations
Know the level of icing for which your airplane is certified
and never intentionally exceed that level.
Never leave the ground with ice or snow adhering to any part
of the airframe.
Never fly in known icing conditions with any anti-icing or de-
icing components inoperable.
When you observe ice on the wings, assume that there is even
more ice on the tail and that it will have a more profound
effect.
Use de-icing and anti-icing components strictly according to
manufacturer's recommendations.
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Use signif icant weather chart(SWC).
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Sectie9 TB 45
Use signif icant weather chart(SWC).
Mod Icing btn FL180en XXX
onderkant SWC !!
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Sectie9 TB 46
2. Turbulence
Definition:
Turbulence isshort-period and small-scale oscillations in wind.
It is very unorganised atmospheric motion including gusts and
lulls in the wind
Aviation definition of the turbulence:
Variations in the wind along the aircraft flight path of apattern, intensity and duration that disturb the aircrafts
attitude about its major axis but do not significantly alter its
flight path.
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The ICAO turbulence definition
Very low below 0.05g Light oscillations
Low 0.05 to 0.2g Choppy; slight, rapid, rhythmic bumps or
cobblestoning
nothing spoiled
Moderate 0.2 to 0.5g Strong intermittent joltscoffee spoiled
Severe 0.5 to 1.5g Aircraft handling made difficult
stewardess spoiled
Very severe above 1.5g Increasing handling difficulty, structuraldamage possible.
aircraft spoiled *
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Types of turbulence:
Convective turbulence
Mechanical or frictional turbulence
Orographic turbulence
Wake turbulence
Clear air turbulence
Frontal turbulence
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1. Convective turbulence
results from convection
dry thermals or CU
CB severe turbulance under, in and above
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2. Mechanical or frictional turbulence
due to obstructions such as steep hills, ridges, buildings,
trees or cliffs along the seashore or inland waters
expected when wind speeds are higher than 20kts
SCHUIFSPANNINGSTURBULENTIE DOOR HWS
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SCHUIFSPANNINGSTURBULENTIE DOOR HWS
DE STRUCTUUR VAN DE WIND
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DE STRUCTUUR VAN DE WIND
TIJD
Hoe dichter bij de grond:
Hoe meer variatie in
richting en snelheid.
De ruwheid* is
zichtbaar aan het
karakter van de wind.
i d
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wind
G
E
B
O
U
W
Op afstand 30 x H nog 25% verstoring op hoogte H
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3. Orographic turbulence
mountainous areas are often turbulent
in areas with marked mountain waves (MTW)Ac
lenticularis
Ac lenticuaris
Rotor cloud
Stable!!!*
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4. wake turbulence
wing-tip vortices
very hazardous, especially during take-offs and landings*
persistent for 5 minutes or even more
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Wing-tip vortices
Walk away from generating aircraft with wind
Hazards:
In flight: possible sudden roll over!
On ground: mainly small aircraft too close behind
big one (wide body)*
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5. Clear air turbulence: CAT
clear air turbulence occurs in the free atmosphere away
from any visible convective activity
mostly associated with a jet stream
in the dense cirrus clouds along jet streams CAT may also occur*
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CAT with upper level
trough and ridge
CAT ith CB clo ds*
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CAT with CB clouds*
USA: keep clear of CB 30 miles.
i ( )
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Mountain waves (MTW)
Alsowithout Ac lenticularis (clear air)
Height of
MTW up to
20 km! *
Effect of MTW up to > 1000 km downwind
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6. Frontal turbulence
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Intensities of turbulence
LIGHT - slight erratic changes in altitude and/or attitude
- slight strain against seat belts or shoulder straps- no difficulty is encountered in walking
MODERATE- changes in altitude and/or attitude
- definite strain against seat belts or shoulder straps
- unsecured objects are dislodged
- food service and walking are difficult
SEVERE - large, abrupt changes in altitude and/or attitude
- aircraft momentarily out of control
- forced violently against seat belts or shoulder straps
- unsecured objects are tossed about
- food service and walking are impossible
EXTREME - aircraft is violently tossed and is practically impossible
to control
- may cause structural damage *
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WINDSHEAR
Definition:
change in windspeed and/or wind direction over short distance
VERTICALE WINDSCHERING (VWS)
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is de verandering van dehorizontalewindsnelheid en/of -richting per lengte-eenheid tussen tweeverticaal bovenelkaar staandepunten.
Horizontaal vlakHorizontaal vlak
H
O
O
G
TE
VWS is dus een snelle verandering over een korte afstand
van de horizontale wind in een verticaal vlak.
D d i d h i l i d lh id / fHORIZONTALE WINDSCHERING (HWS)
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De verandering van dehorizontalewindsnelheid en/of -richting per lengte-eenheid tussen twee punten, die beideninhetzelfde horizontale vlakliggen.
HORIZONTALE BREEDTE HORIZONTALE BREEDTE
HORI
ZONTALE
LENGTE
HORI
ZONTALE
LENGTE
HWS is dus een snelle verandering over korte afstand van de
horizontale wind in een horizontaal vlak.
Voetbalveld.
SCHERING VAN DE VERTICALE WIND (SVW)
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De verandering van deverticalewindsnelheid en/of -richtingper lengte-eenheid tussen twee punten, die inhetzelfde
horizontale vlakliggen.
HOOGT
E HOOGT
E
BODEM BODEM
SVW is dus een snelle verandering over korte afstand
van de verticale windcomponent in een horizontaal vlak.
WINDSCHERINGSVARIATIES TOEGEPASTOP DE LUCHTVAART
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OP DE LUCHTVAART
Windschering (windshear)is de variatie in grootte van dewindvector of zijn componenten langs en dwars op devliegroute.
Men onderscheidt: Head- of tailwindshear, de variatie in sterkte van de
neus- of staartwind-component;
Crosswindshear, de variatie van de dwarswind-
component en Vertical windshear, de variatie van de verticale
windcomponenten.
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Types of windshear
1. Nocturnal type; occurs during the night and in the early morning
in undisturbed radiation weather
2. Synoptic type; usually associated with fronts, but they also occur
otherwise
3. Orographic type; caused by orographic influences
4. Thunderstorm type; in and near thunderstorms associated with gust
fronts, downbursts, microbursts, macrobursts,
outbursts
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Sectie9 TB 71
http://www.youtube.com/watch?v=OtnL4KYVtD
E&feature=related
Sh I i !
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Sectie9 TB 72
Shear on Inversions!
T Wind
21008 kt
25018 kt
NACHTELIJK WINDMAXIMUM een voorbeeld van vws
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NACHTELIJK WINDMAXIMUM, een voorbeeld van vws
x 1000 ftx 100 ftX 1000 ft
Top inversie
DAG
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http://www.metacafe.com/watch/30410/boeing_747_extreme_landing/
http://www.metacafe.com/watch/30410/boeing_747_extreme_landing/http://www.metacafe.com/watch/30410/boeing_747_extreme_landing/7/28/2019 Section 9 TB meteorology
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Synoptic type
associated with cold and warm fronts
FRONTALE WINDSCHERING, een ander voorbeeld van
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VWS
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the sea-breeze front
What shear?
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Orographic type
mountain waves may lead to severe turbulence and windshear
Thunderstorm type
thunderstorms and cumulonimbus can cause the most severe
windshears
all kinds of windshear can happen
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GEBIED MET BERGGOLVEN
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Strong winds (>30 kts)Perpendicular to mountains
Stable atmosphere
DRY ROTOR
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DRY ROTOR
Axis?
STERKTE VAN DE WINDSCHERING
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Sectie9 TB 82
De ICAO geeft de volgende kwalificatie van de sterktevan windschering:
Zwakke windschering bij 0 - 4 kt /100 ft
Matige windschering bij 5 - 8 kt /100 ft
Sterke windschering bij 9 - 12 kt /100 ft
Zware windschering bij 12 kt /100 ft
Thunderstorm type
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yp
thunderstorms and cumulonimbus can cause the most severe
windshears
all kinds of windshear can happen
Downdrafts, microbursts, macroburst, gustfront, rollcloud etc
DE DOWNDRAUGHT ( Amerikaans: downdraft)
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DE DOWNDRAUGH ( Amer kaans downdraft)
In de onderste helft en onder de bui kan een krachtigeneerwaartse stroming ontstaan.
De algemene term ervoor is downdraught.
De algemene term van de voor de luchtvaart gevaarlijkevorm heet downburst.
ONTSTAANSOORZAKEN VAN DEDOWNDRAUGHT
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DOWNDRAUGHT
In de wolk : Afkoeling van de lucht door het smelten van ijsvormige
neerslagelementen onder het 0 0c-niveau. Meesleuren van de lucht tussen de neerslag-elementen.
Onder de wolk: Afkoeling van de lucht door het verdampen van de
vloeibare neerslagelementen. Meesleuren (drag) van de lucht tussen de neerslag-
elementen.
SOORTEN DOWNDRAUGHT
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MACROBURST:Een krachtige neerwaartse stroming met eendoorsnede > 4 km.
Komt voor in het gebied met de zwaarste neerslag.
Kan in een groot gebied tornado-achtige schadeaanbrengen.
Aan de grond kan de windsnelheid oplopen tot 130 kt.
De levensduur varieert, vanaf het moment dat de grond isbereikt, van 5 tot 20 minuten.
SOORTEN DOWNDRAUGHT (vervolg 1)
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MICROBURST:Een zeer krachtige neerwaartse stroming met eendoorsnede 4 km.
Komt voor in het gebied met de zwaarste neerslag.
De verticale snelheid kan 30-60 ft boven de grond 1000-2000 ft/min (5-10 m/s) bereiken.
Aan de grond kan de windsnelheid oplopen tot >160 kt.
De levensduur varieert, vanaf het moment dat de grond isbereikt, van 2 tot 5 minuten.
SOORTEN DOWNDRAUGHT (vervolg 2)
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SOORTEN DOWNDRAUGHT (vervolg 2)
MIDAIR MICROBURST:Een microburst die het aardoppervlak niet bereikt en deluchtstroming daar niet benvloedt.
DROGE MICROBURST:Een microburst uit een bui met een hoge basis, waarvande regen verdampt voordat die het aardoppervlak kanbereiken. De microburst bereikt het aardoppervlak
echter wel.
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FOOTPRINT VAN EEN DOWNBURST UITEEN STATIONAIRE BUI
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EEN STATIONAIRE BUI
Gustfront van de horizontaal
uitstromende koude lucht
Omtrek bui
Centrum
downburst
FOOTPRINT VAN EEN DOWNBURST UITEEN BEWEGENDE BUI
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EEN BEWEGENDE BUI
Bewegingsrichting
Omtrek bui
Gustfront van de horizontaal
uitstromende koude lucht
Downburst
centrum
EVOLUTIE VAN EEN DOWNBURST
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0 3 5 10 15
Verlopen tijd in minuten
Onderkant van de bui
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WINDSCHERINGSDETECTIE
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Er zijn drie operationele windscherings-systemen ingebruik op de grond:
Low Level Windshear Alert System( LLWAS)
De windprofiler,een Doppler-radar
SODAR,een akoestische radar
In gebruik of in ontwikkeling voor airborne systemen:
Doppler-radar
Infrarood detectiesysteem
Laser detectie systeem
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horizontal windshear
vertical windshear
shear of the vertical wind
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GET OUT !!!!
Effect of windshear on flight:
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Effect of windshear on flight:
Windshear is the variation of the components of the wind
vector along and perpendicular to the flight route.
Head windshear / tail windshear: variation of the windspeed of the
head/tail wind.
Shearing of vertical wind: variation of the vertical wind.
Cross windshear: variation of the wind component perpendicular to
the flight route.
Windshear in practice:
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Windshear in practice:
Often simplified to Negative or Positive Shear
Positive: performance increase, more lift, greater IAS
Negative: performance decrease, less lift, smaller IAS.
THUNDERSTORMS (onweersBUI*)
USA STORM i BUI !!!!!
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USA STORM is een BUI !!!!!
Conditions for thunderstorm development
a thunderstorm is a CB accompanied by thunder and lightning.
1. Most of cloud must be above the FZL => WBF
2. atmosphere must be unstable , at least 10.000 ft, strongupdraft, 10-35 m/s
3. top of the clouds above the level of -20C (not necessary in
the tropics)
4. Sufficient lifting forces
5. adequate supply of moisture from below
lifting forces can be caused by:
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g y
- local differential heating over land, solar insolation and formation
of thermal lows
- night time radiation cooling from the top
- orographic effects (lifting)
- frontal activity (frontal lifting)
- low level convergence, along a trough for example
- due to differential advections: cold air advection aloft and warm air
advection in low levels.
Life cycle of an individual thunderstorm cell
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Life cycle of an individual thunderstorm cell
Single Cumulonimbus cells rarely exceed a few km in diameter
In the individual cell three stages of development can be recognised:
1. Cumulus stage
2. Mature stage3. Dissipating stage
The life cycle of an individual cell is in the order of 30 minutes
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1 C l t
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1. Cumulus stage
only updrafts
no precipitation
10-15min duration
1. Cumulus stage
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CU and TCU
Only updrafts
No precip.
Higher FZL in
CLD
2 Mature stage
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2. Mature stage
up- and downdrafts
precipitation
downburst and outburst
gust front
hail, turbulence,
lightning and gusts
greatest activity of the stormsand thunderstorms
Max vertical speeds 3040 m/s
2. Mature stage
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both down and updrafts
often tilted!*
FZL higher in updrafts
1) Warm air updraft
2) Release of latent heat
FZL lower in downdrafts
1) Drag of cold upper air
2) Melting and evaporation
need energy
3. Dissipating stage
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3. Dissipating stage
downdrafts dominate
precipitation decreases
and finally stops
no more lightning
turbulence inside the
cloud will rapidly decrease
Clouds dissolve
Anvil- Ci clouds often remain
longtime
Classification of thunderstorms
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Sectie9 TB 110
Classification of thunderstorms
Air mass thunderstorms
Thermal thunderstorms, a result of irregular local heating of
the surface. Uplift due to solar radiation.
Cold mass thunderstorms:thunderstorms or night/ winter
thunderstorms over sea and coastal areas. They often occur at
the rear of a cold front. The temperature in the higher layers islow, causing a steep environmental lapse rate.
Orographic thunderstorms: when moist potentially unstable
air is forced to rise against a mountain range, it becomes
statically unstable.
Prefrontal thunderstorms: in unstable airmass ahead of a kata
cold front (fast running front), generally organised along a
squall line.
Example Pre-frontal TS
Sly warm flow
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Often Thermal
Low beforeColdfront arrives
y
over W Eur
Very hightemperatures
over France
F t l th d t
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Frontal thunderstorms
When the warm air in the warm sector is unstable, the forced lifting along
the frontal surface may lead to the formation of embedded cumulonimbusin the frontal clouds along the front at the surface. They are not random
but organised along a line along the surface front. They are associated
with active cold fronts.
Convergence thunderstorms
These thunderstorms are observed along the ITCZ, an E-ly wave, a
trough and if the airmass is potentially unstable there is also a risk of
thunderstorms along the sea-breeze front.*
Frontal thunderstorms
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Mostly on Coldfronts
stratiform
Convergence thunderstorms
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Trough
L
surfaceTrough
CB
Convergence thunderstorms
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May develop near/in:
1. ITCZ
2. Troughs
3. Lows
4. Easterly Waves
5. Cyclonic cols
6. Etc
Frequency of thunderstorms
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Thunderstorms are wide spread, around 50 000 thunderstorms
per day !! The frequency of thunderstorms over land is highest in
summer during daytime; over sea the frequency is highest in
winter during the late night.*
The frequency of occurrence changes from one region to another
- In Polar areas: nearly no thunderstorms
- Between latitudes 70-80: 1 day a year with thundery weather.- In mid-latitude: 32 days with thundery weather.
- In subtropical areas: only 10 days
- Near equator: 136 days with thundery weather.
Thunderstorm Classification
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Single cell/ Airmass
Multi cell
Super cell
Squall lines
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Single cell or Airmass TS
Lifetime to 1 hour
3 to 8 km diameter
Multi cell TSUpper wind
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By growing new cells on forward right side, system moves
to the right of upper winds!
Upper wind
Movement
New cells
Oldest Cell
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Multi cell TS
Often called MCC or MCS (depending on size)
(Mesoscale Convective Complex or System)
Anvils up to 100 km away
Up to 300 x 300 km!
Lifetimes up to 12 hours
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Sectie9 TB 122
Fig. 8.49 Schematic of an idealized multicell storm developing in an
environment
with strong vertical shear in the direction of the vertically averaged wind. The
vertical profile of equivalent potential temperature e in the environment is
shown at the left, together with the wind profile. Arrows in the right panel
denote motion relative to the moving storm.
Super cell
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Sectie9 TB 123
Acts as a Low
Rotation
Very big
Very active
ONE CELL
Tornados
Rare in Europe
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Sectie9 TB 124
Fig. 8.56 Structure of a typical tornadic supercell storm. Motion of the warm air is
relative to the ground. [Based on NOAA National Severe Storm Laboratory
publications and an unpublished manuscript by H. B. Bluestein. From R. A.
Houze, Cloud Dynamics, Academic Press (1993) p. 279.]
Supercell 26 juli 1983
moving NNE
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Developing MCC
Bigger than the
NetherlandsHail at 07.00 Lt Den
Helder golfball size
Well developed Low
on sfc charts
2,5 m water upset
Harlingen*
Squall lines
Squall= sudden wind
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More or less closed LINE
of active CBs moving in
one direction
>200 km long Gustfront up to max 32
km in front of Squall line!!
Rotor/Arcus cloud
Sand or dust rotor
Next cross section A-B
icrease to >16 kts lasting
1 min at least
cross section A-B
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Sectie9 TB 127
Cold air from shower giving gustfront
Warm air to shower to feed CB
09024
24032G46Gustfront
Squall lines
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Sectie9 TB 128
formed near:
1. cold fronts
2. troughs
3. ITCZ
Squall lines develop mostly in hot summer weather along
lines of convergence or pre-frontal convergence.
When all active TS condition are met.*
The gust front
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Outflow of cold air in a (thunder)shower
dangerous for aircraft on takeoffs and landings
HWS and VWS
24 to 32km
ahead of the
storm centre
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Rolwolk!
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GET OUT!
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Hail
H il i f f i i i hi h i f b ll i l
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Hail is a form ofprecipitation which consists of balls or irregular
lumps of ice (hailstones). Hailstones on Earth usually consist mostly
ofwater ice and measure between 5 and 50 millimetres in diameter,with the larger stones coming from severe thunderstorms.[1] Hail is
always produced by cumulonimbi (thunderclouds), usually at the
front of the storm system, and is composed of transparent ice or
alternating layers of transparent and translucent ice at least 1 mmthick. Small hailstones are less than 5 mm in diameter, and are
reported as SHGS. Unlike ice pellets, they are layered and can be
irregular and clumped together.
Wikipedia
Hail development:
1) Precip partical
http://en.wikipedia.org/wiki/Precipitation_%28meteorology%29http://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Icehttp://en.wikipedia.org/wiki/Millimetrehttp://en.wikipedia.org/wiki/Thunderstormhttp://en.wikipedia.org/wiki/Cumulonimbushttp://en.wikipedia.org/wiki/Snow_pelletshttp://en.wikipedia.org/wiki/Ice_pellethttp://en.wikipedia.org/wiki/Ice_pellethttp://en.wikipedia.org/wiki/Snow_pelletshttp://en.wikipedia.org/wiki/Cumulonimbushttp://en.wikipedia.org/wiki/Thunderstormhttp://en.wikipedia.org/wiki/Millimetrehttp://en.wikipedia.org/wiki/Icehttp://en.wikipedia.org/wiki/Earthhttp://en.wikipedia.org/wiki/Precipitation_%28meteorology%297/28/2019 Section 9 TB meteorology
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) p p
enters updraft
2) Riming startsabove FZL
3) Heavier particle
falls down, melts
partialy below FZL
4) Enters updrafts
againriming
5) Etc etc
Second posibility:
Riming hailstone stays at same level
Updraft = fallspeed growing by riming
Hail development:
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Melting and freezing,
Melting and freezing
Thats why a hailstone is layered..!
Hail
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due to strong updraft a melting snowflake will go up and down
for several times and freeze due to riming proces
Hailstones can achieve a large size and can be met at any height
in the cloud(45.000 ft) and outside the cloud!!!!
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Flying below anvil close to CB dangerous for hail!!
Hail
F t f it !!!
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From a pea to a grapefruit !!!
6 cm
Nederland
17 cm
Max ca. 20 cm.USA
Hagelfeiten.De grootste hagelsteen die in de wereld viel had een doorsnedevan 17,8 centimeter. De hagelsteen viel op 22 juni 2003 in Aurora(N b k ) D t k t lh id 160 kil t
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(Nebraska). De steen kwam met een snelheid van 160 kilometerper uur neer.
De zwaarste hagelsteen viel op 3 september 1970 in Coffeyville(Kansas) en woog 757 gram. Het ijsblok wordt bewaard in eenvriezer in Boulder en staat vermeld in het Guinness Book of WorldRecords. Van de hagelsteen is een plastic replica gemaakt, zodat
iedereen het kan zien.
Ook een grote hagelsteen viel in Potter (Nebraska) op 6 juli 1928en was 13,7 centimeter.Ooggetuigen zeiden dat tussen de individuele hagelstenen 3 tot4.5 meter ruimte zat.In juli 1990 werd Denver (Colorado) door zware hagel getroffen.Hier was voor $625 miljoen recordschade.Idem ca. 15 jaar geleden in Munchen
Large hailstones can cause enormous damage to aircraft
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http://www.youtube.com/watch?v=wZr8jXo1Uso
The anvil
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Top of CB
Anvil points in the direction of the winds in the top of theCBs, and so indicates the direction of the cell motion
anvil
Electricity in the atmosphere
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There is always some weak electrical charge in
atmosphere
In clouds the ice particles make the difference
Electricity in the atmosphere PRINCIPLE*
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Sectie9 TB 152
*collides with
* *Large negativefall
* Small positive rise
- - - -- - - -
+ + + +
+ + + +
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Sectie9 TB 153
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Sectie9 TB 154
Sometimes an aircraft is a bridge/trigger for
discharge to the ground:
Selftriggering effect *
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Sectie9 TB 155
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Sectie9 TB 156
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Words to know
1) Stepped leader2) Leader
3) Streamer
4) Return strokeBlz 9-42
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Sectie9 TB 158
Lightning damage on propellor tip
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(Airborne) Radar To high
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Proper tilt is essential
To high
To low
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Shadowing
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Sectie9 TB 162
radar CB1 CB2
On the scope:
Only CB1
CB1
Attenuation
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Sectie9 TB 163
radar
By absorbtion of radar energy, false backside
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Sectie9 TB 164
Turbulence: in and close to Rotors*in and close to Lenticularis
in waves
Downbursts, micro- and macro
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Famous:
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Famous:
Fujita and Caracena 1977
1) Eastern 902
2) Eastern 66
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Tornados
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Tornados Neerslaggebied
Groen/geel
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Sectie9 TB 170
Let op: echos in
de vorm vanboog of
komma (Eng
Hook Echo)
Tornado
mogelijk
GET OUT!!!
Tornados
Twister, wervelwind,
zware windhoos etc
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A tornado is defined as aviolently rotating column
of air extending from a
thunderstorm to the
ground.
zware windhoos etc
Diameter 10 to 100 m normaly
Max around 2 km!!
Rotating windspeed:100 to 150 m/s (550 km uur)
Damaging path: 10 km average
Low pressure inside (900 hPa avg)*
Waterspout (little
tornado over
warm water)
Warm air moves UP !!!
Tornados
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Whole CB system rotates
Most Tornados rotate (99%) Cyclonic (Coriolis)*
Whole world knows Tornados
Mostly in the Tornado Alley USA
Tornados
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Tornado Alley
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CBs need moisture and heat, so mainly form over agricultural areas
Tropical jungles are not hot enough.
Desserts are not moist enough.
Tornado from Tornado
Alley
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Let op schuine stand !
Moerdijk F28*
Tornadoes in Nederland?
1) Borculo augustus 1925 de cycloon van Borculo 3 doden
2) N d 1927 10 d d
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2) Neede 1927 10 doden
3) Tricht 1967 7 doden
4) Ameland 1972 4 doden
5) Moerdijk ongeluk 1981 F28 verongelukt 2 slurven onder bui
6) Ameland 1992 1 dode*
7) Plus nog ca. 25 kleinere windhozen, waterhozen, downbursts
etc. met schade per jaar!
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Bron KNMI
Tornado van Tricht
Rotation speed of air defines Fujita scale: (for Tornados)Fujita
schaal
F064-117 Schade aan schoorstenen, takken
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F0km/u breken af
F1118-180
km/u
Schade aan daken, autos worden van
weg afgeduwd
F2
181-
251
km/u
Bomen worden ontworteld, caravans
vernield
F3
252-
330
km/u
Daken en muren worden weggerukt,
autos worden opgetild
F4
331-
417
km/u
Huizen worden vernield en autos
gegooid
F5
418-
509
km/u
Huizen worden van fundamenten
gelicht
Dustdevils
(Wind- of stofhoos)
A li
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In Australia:
Willy Willy
Only Thermals (often Dry thermals = no cloud)
( droge thermiek of Blau thermiek)
Dustdevils can cause gusts up to 35 kt ! *
Dustdevil boven verbrande aardeLet op: altijd mooi weer
F t T A d B
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Foto: T.A. de Boer.