Gangguan Tropis

(1)

Gangguan Cuaca

Gangguan Cuaca W

Wilayah

ilayah

T

(2)

Systim Cuaca wilayah

Systim Cuaca wilayah tr

tropis secara

opis secara

umum dibagi menjadi

umum dibagi menjadi 2 k

2 kelas

elas

•

Sistim cuaca umum terkait

sirkuasi atmosfer

seperti

subtropical high, tr

subtropical high, trade wind,

ade wind, IT

ITCZ,

CZ,

monsoon

•

Gangguan cuaca tropis dan

subtropis seperti

siklon tropis,

gelombang tropis, monsun

gelombang tropis, monsun depresi

depresi

dan low, !"#, $%#, hujan mesoscale,

hujan sistim kon&eksi, cloud cluster,

s'uall lines, &ortisitas

(3)

Systim Cuaca wilayah

Systim Cuaca wilayah tr

tropis secara

opis secara

umum dibagi menjadi

umum dibagi menjadi 2 k

2 kelas

elas

•

Sistim cuaca umum terkait

sirkuasi atmosfer

seperti

subtropical high, tr

subtropical high, trade wind,

ade wind, IT

ITCZ,

CZ,

monsoon

•

Gangguan cuaca tropis dan

subtropis seperti

siklon tropis,

gelombang tropis, monsun

gelombang tropis, monsun depresi

depresi

dan low, !"#, $%#, hujan mesoscale,

hujan sistim kon&eksi, cloud cluster,

s'uall lines, &ortisitas

(4)

#utline

•

Gelombang wilayah Tropis

•

(orte) *skala sinoptik+

•

(5)

e-nisi Tropis

•

e-ni geogra-s . wilayah yang terletak

diantara lintang 2/0 1 dan 2/0 S

•

e-nisi astronomis . merupakan wilayah

lintang dimana matahari dalam

lintang dimana matahari dalam perjalanan

perjalanan

semunya pernah berada tepat tegak lurus

diatas wilayahnya

•

e-nisi meteorologi . merupakan wilayah

yang

yang memeiliki

memeiliki cuaca

cuaca relati

relati k

konsisten

onsisten

terjadi setiap tahunya *misal angin pasat+

(6)

(7)

aya tarik cuaca wilayah

tropis

•

Tempat terjadinya enomena cuaca

yang paling menghancurkan yaitu

siklon tropis

•

$erupakan dapurnya *mesin panas+

sistim cuaca global

•

3danya enomena monsun

•

3danya enomena 41S#

•

3danya enomena $%#

(8)

6orum internasional

•

Global 3tmospheric 7esearch

8rogram *G378+ atlantic tropical

e)periment

•

$onsoon 4)periment *$#149+

•

Tropical 3tmosphere : Global #cean

*T#G3+

•

Coupled #cean : 3tmosphere

(9)

5arakteristik cuaca tropics

• Secara umum bersiat musiman dengan ciri panas dan

lembab saat musim panas dan dingin dan kering saat musim dingin

• 1amun sesekali karakteristik tersebut tergagnggu dengan

munculnya gangguan tropis yang berskala mulai dari gangguan gelombang atmoser skala sinoptik yang

terbentuk di tradewind yang bergabung kedalam sirkulasi sekitar ekuator melalui sistem tekanan rendah, dan

beberapa badai lokal yang dipicu oleh skala meso dan skala lokal

• i wilayah tropis, jauh dari pengaruh jet stream lintang

menengah, angin bertiup dari timur ke barat

• Cuaca di daerah tropis relati stabil dari hari ke hari, angin

bertiup pada kecepatan yang relati konstan, yaitu dari ;0 sampai /< km=h Terdapat banyak awan kumulus, bahkan saat cuaca cerah i daerah dekat e'uator, awan ini

membesar sejak pagi hingga siang, menghasilkan hujan harian di hutan, dan hujan lebat yang tiba>tiba di ITCZ

(10)

• Cuaca di wilayah subtropis *sekitar ;<?@A sampai 20?@A

dan ;< ?@S sampai 20?@S+ tidak selalu ramah Tropis di wilayah tersebut terganggu oleh pertumbuhan siklon

• 4'uator menerima jauh lebih banyak energi dari matahari,

daripada yang bisa ia radiasikan ke angkasa Terkadang sirkulasi normal atmoser tidak cukup untuk menjaga keseimbangan

• ITCZ membuat eeknya terasa dalam bentuk siklon tropis • Sistem ini berawal sebagai sebuah palung, dengan

pembelokan siklonik dari tiupan angin 3wan dan hujan menyertai gelombang timuran ini, dan sistem berpindah dari timur ke barat

• %ika intensi-kasi terjadi, sebuah sistem tekanan rendah

yang tertutup dan berotasi, dinamakan tropical

depression, muncul, dan kemudian presipitasi meningkat Sirlkulasi ini bisa terkonsentrasi, menghasilkan angin

(11)

(12)

•

Sistem cuaca tropis membantu transer panas dari

ekuator ke kutub, yang sumber panasnya diperoleh dari

sabuk lintang antara ;<?@A dan ;<?@S, yang

merupakan bagian yang selalu tertutup awan

cumulonimbus raksasa

•

Selain itu, membantu dalam menjaga keseimbangan

panas bumi, diantaranya dengan adanya run oB dari

daratan ke lautan, sirkulasi osean, sirkulasi atmoser,

dan transer panas dari palung ekuator

•

Sistem ini juga menyediakan banyak hujan yang

dibutuhkan di area kering seperti di Te)as dan $e)ico

1amun juga dapat menghasilkan siklon tropis yang

menyebabkan kerusakan karena angin kencangnya,

yang berkecepatan sekitar /2< km=h, di beberapa

kasus ekstrim Selain itu, banyak bencana lain

disebabkan oleh kekasaran dan tinggi lautan yang

dihasilkan oleh angin dan pusat tekanan rendah

(13)

; Gelombang wilayah

Tropis

• Tropical wa&es, easterly wa&es, or tropical easterly wa&es,

also known as 3rican easterly wa&es di wilayah 3tlantic, 3dalah merupakan palung wilayah tropis *trough+, atu

gelombang angin yang terbentang sepanjang area tekanan rendah, berorientasi utara selatan, yang bergerak dalam arah timur : barat melintasi wilayah tropis yang

menyebabkan area perawanan dan thunderstorm *TS badai guntur+

• Gelombang tropis melakukan perjalanan ke arah barat

karena adanya angin timuran sepanjang wilayah tropik dan subtropik

• Gelombang tropis dapat tanda awal akan adanya siklon

tropis di utara 3tlantik dan kolam pasi-k bagian tenggara

• Gelombang tropis digenerate oleh pemanasan=kon&eksi

(14)

(15)

•

"erkembang dengan intensinya pelepasan

panas laten

•

$emiliki kecepatan rambat D m=s

•

ari yang teramati di stasiun akti-tas

gelombang tropis ditandai dengan adanya

pergantian arah yang tajam dari sirkulasi angin

ke arah yang berlawanan

•

"isa terjadi di lapisan permukaan atau di lapisan

atas

•

Semakin banyak kejadian gelombang tropis

(16)

•

They begin appearing as early as 3pril=$ay and

continue until #ctober=1o&ember

•

nearly E< occurring per year

•

They ha&e wa&elengths o appro)imately 2<<<

to F<<< km and periods o roughly />F days

•

4asterly wa&es are the seeds rom which

tropical systems grow 3ppro)imately E< o

tropical storms and minor hurricanes

*categories ; or 2+, and nearly D0 o major

hurricanes *category /, F, or 0+ originate rom

easterly wa&es

(17)

(18)

(19)

(20)

(21)

(22)

(23)

There are se&eral conceptual models or

wa&es in the easterlies These are.

•

7iehlHs classical model : 3pplies mainly

to Caribbean wa&es

•

6rankHs in&erted (J model : 3pplies to

eastern and mid>3tlantic wa&es

•

3rican wa&e model : 3pplies to wa&es

o&er 4'uatorial 3rica and the western

coast o 3rica

(24)

Wa&es in the 4asterlies are primarily a

1orthern Kemisphere phenomena

•

This is because they need deep,

easterly current to orm an

propagate, and these are more

pre&alent in the 1orthern

Kemisphere &ersus the Southern

Kemisphere

(25)

Gangguan Skala $eso dan badai

skala lokal di wilayah tropis

•

"erdiameter ;<< s=d ;<<<km

•

Contoh . thunderstorms, hailstorms,

tornadoes and s'uall>lines

•

Terjadinya karena adanya

(26)

$ekanisme

pembentukannya

•

The e)istence o a conditionally unstable

atmosphereL

•

Moisture convergence

at low le&elsL and

•

3n eBecti&e mechanism to raise the low>

le&el moisture to higher le&els and release

the latent heat o condensation or urther

growth o the cloud through penetrati&e

con&ection, the net eBect o which is

an

adiabatic warming

o the en&ironment by

(27)

Thunder storm

•

inamakan thunder karena peristiwa

tersebut menghasilkan badai, kilat,

angin kencang, hujan lebat, badai

hail, bahkan bisa berlanjut menjadi

tornado

•

TS mendapatkan energinya dari

potensial energi kondisi atmoser

yang labil dimana eki&alen dengan

penurunan temperatur secara

(28)

• "adai atau storm, menurut $cGraw Kill 8roessional . Science and

Technology 4ncyclopedia adalah 3n atmospheric disturbance in&ol&ing perturbations o the pre&ailing pressure and wind -elds on scales ranging rom tornadoes *<E mi or ; km across+ to

e)tratropical cyclones *;2:;M<< mi or 2:/<<< km across+L also, the associated weather 

• e-nisi lainnya dari 4ncyclopedia o Columbia Ani&ersity 8ress

menyatakan, Ndisturbance o the ordinary conditions o the atmosphere attended by wind, rain, snow, sleet, hail, or thunder and lightning

• Types o storms include the e)tratropical cyclone, the common,

large>scale storm o temperate latitudesL the tropical cyclone, or hurricane, which is somewhat smaller in area than the ormer and accompanied by high winds and hea&y rainsL the tornado, or

twister,J a small but intense storm with &ery high winds, usually o limited durationL and the thunderstorm, local in nature and

accompanied by brie but hea&y rain showers and oten by hail The term storm is also applied to bliOOards, sandstorms, and dust

storms, in which high wind is the dominant meteorological elementNJ

(29)

5arakteristik thunder storm

•

When &iewed rom outside, a thundercloud may

appear as a single large cloud>mass

•

diameter o a ew kilometres *usually ;<:;2 km+ and

top rising to great heights, sometimes e&en beyond

the tropopause at ;E:;D km

•

@asting or a ew hours

•

during the de&eloping stage, updrats dominate o&er

downdrats inside the cloud

•

"ut when precipitation starts alling through the

cloud downdrats increase and ultimately dominate

o&er updrats, thereby signalling the demise o the

thunderstorm

(30)

•

The general distribution o updrat &elocity with

height in the central portion o a growing cumulus

cloud and a mature cumulonimbus cloud and the

radial distribution o updrat &elocity rom the

central region to the periphery o a cloud o

horiOontal e)tent o D km at the height o ma)imum

updrat at about M< km

•

The &ertical distribution 6ig 2M*a+ shows that there

is a gradual increase o updrat &elocity rom a

&alue o about 0 m=s at height ;0 km to 2< m=s at

D:;< km and then a gradual decrease to low

&elocity alot

•

the ma)imum updrat o about ;D:2< m=s occurs

near the center o the storm with a gradual

decrease o the &elocity to a &alue o 2:/ m=s at

about /0 km rom the center

(31)

Tahapan proses pembentukan endapan di dalam awan badai

• The updrats in a thundercloud lit moisture to diBerent le&els o the

atmosphere leading to ormation o water substances in diBerent phases o water

• In the -rst stage, as moist air is lited to le&els abo&e the

condensation le&el at about ;0 km, water &apour condenses on the e)isting cloud condensation nuclei to orm cloud drops

• Some o the drops increase in siOe as they are carried upward by

collecting smaller drops and deposition o new water &apour round

them but they remain in li'uid orm till they reach the reeOing le&el at about 0 km

• 3bo&e the reeOing le&el, drops donHt reeOe immediately, since they

can remain in a supercooled state to a temperature as low as :F<PC

• Kowe&er, as they are lited by strong updrats to the cooler regions o

the upper troposphere, an increasing number o them turn into snow crystals

• "eyond a height o about ;< km, most o the snow crystals turn into

ice crystals

(32)

8recipitation, owndrat and S'ualls

• The water substances inside the storm in the orm o supercooled water

drops, snow and ice crystals, ater they grow to large siOes, start alling through the cloudmass under their own weight with a &elocity which depends upon the updrat &elocity and the aerodynamic properties and resistance o the en&ironmental air through which they all

• 3s they all through the reeOing le&el, the ice and snow crystals begin

melting by drawing heat rom the warmer en&ironment and thereby cool the air through which they all by e&aporation rom their suraces

• The result is a downdrat o e)tremely cold air in the precipitating part o

the cloudmass

• #n reaching the ground along with large drops o rain and sometimes

pellets or hailstones, the downdrat spreads in all directions producing s'ually winds

• In meteorology, a s'uall is de-ned as a strong wind characteriOed by a

sudden rise o its &elocity to ;E knots or more which is sustained or at least two minutes

• S'ualls o abnormally high winds can do a lot o damage to lightly>built

(33)

@ightning and Thunder

•

Lightning and thunder are two most

characteristic properties of a thunderstorm



•

@ightning is an electrical discharge that occurs

between two oppositely charged regions inside a

cumulonimbus cloud, or between the cloud and the

earthHs surace

•

The basic re'uirement is a separation o electric

charges between two parts o the cloud and build>

up o a strong electrical -eld between them

•

"y induction, the -eld produces a path o ion>

(34)

(35)

(36)

(37)

• $ore than hal o all lightning discharges take place inside

the cumulonimbus clouds and are known as intracloud discharges

• "ut, lightning also occurs between the cloud and the ground

which are known as streak or orked lightnings

• "ecause o its intrinsic interest in the conte)t o harmul

eBects upon li&ing creatures by way o death and

destruction, ignition o orest -res, and disturbances to power and electrical communications, etc,

• the cloud>to>ground lightning has been studied more

e)tensi&ely than any other orm o lightning

• $ost o the electrical energy in a lightning discharge goes

into producing heat

• It is estimated that air along the path o a lightning

discharge may be raised to a temperature e)ceeding

;<,<<< C o this heat energy goes into producing radiation and light, while a part goes into producing sound wa&es

through longitudinal compression and rareaction which we hear as thunder

(38)

• @ightning acti&ity o&er the globe is belie&ed to contribute

importantly to the maintenance o the earthHs electric -eld

• It is well>known that the ionosphere which is positi&ely

charged loses its charge continuously to the ground which is negati&ely charged

• This implies that unless replenished regularly, the ground

will soon lose its negati&e charge and the atmosphere will lose its electric -eld

• It is belie&ed that this re'uirement is ul-lled by lightning

acti&ity o&er diBerent parts o the globe, which supplies the much>needed negati&e charge rom the cloud to the

ground

• The cloud also sends positi&e charge rom its upper part to

the ionosphere

• The harmul eBects o lightning strikes can be minimiOed

by keeping indoors during a thunderstorm

• It is a common practice in most parts o the globe to erect

lightning rods in buildings in order to protect them rom possible damage rom lightning strikes

(39)

(40)

S'uall @ine

•

3 s'uall line is a line o acti&e thunderstorms which

may be continuous or with breaks o&er a length o

;<< km or more

•

It is accompanied by all the characteristics usually

associated with a thunderstorm, &iO, strong

updrats and downdrats, precipitation, lightning,

thunder and s'ualls

•

It is a type o meso>scale con&ecti&e se&ere local

storm system which is usually associated with

mo&ing winter cold ronts and summertime troughs

o airmass discontinuity

•

It is distinguished rom other types o se&ere local

(41)

(42)

(43)

(44)

Kailstorms

•

3 hailstorm is a mature thunderstorm

rom which signi-cant hailstones all to

the ground

•

The siOe o hailstones can &ary rom 0

mm to ;0 cm or more in diameter the

largest o the round hailstones was F/

and weighed ED; g

•

3 cumulonimbus is the only type o

(45)

(46)

(47)

(48)

(49)

•

Kailstorms are o intrinsic interest because o

their destructi&e power

•

They are known to inQict damage to aircrat in

Qight and standing crops on the ground

•

They can also destroy plant and animal lie

•

There was once a report o a hailstorm in

7ajasthan in India which wiped out a big herd o

cattle comprising o giant>siOe buBaloes graOing

in the -eld

•

#n 2R $ay, ;M0M, an Indian 3irlines aircrat Qying

at 0R<< m asl near elhi in India was caught up

in a hailstorm and the hailstones encountered

caused holes in the aircrat, the largest o which

had a diameter o about ;0 cm *Saha, ;ME2+

(50)

5arakteristik Kailstones

• 3 hailstone consists of concentric shells o opa'ue and clear ice • It forms in con&ecti&e clouds the tops o which reach great heights

in the atmo>sphere In the tropics, the tops o cumulonimbus clouds ha&e been known to e)tend to ;2:;0 km asl or e&en greater heights

• The mean distribution o updrats in towering cumulus and

cumulonimbus clouds is such that there is a gradual increase o updrat &elocity rom a &alue o about 20 m=s at height ;0 km to about ;< m=s at D:;< km and then a gradual decrease to lower &elocity alot *"yers and "raham, ;MFM+

• 3ll thunderstorms do not precipitate hailstones, although it is

generally agreed that the e&olution o an ice phase is a common eature o all thunderclouds #bser&ations show that only a &ery small proportion o e&en the se&erest thunderstorms yield large hailstones

• There is a pronounced geographical and seasonal &ariation in the

distribution o hailstones In general, thunderstorms occurring in particular areas and seasons only yield hailstones

(51)

•

In the siOe>spectrum, hailstones o &ery large

diameter are ound to occur in low concentration

*;=m/ or less+

•

$ost oten, hailstones are obser&ed to all earlier

than raindrops Sometimes they all simultaneously

•

Kail starts rather suddenly and usually lasts rom a

ew minutes to less than hal an hour

•

There may be se&eral ups and downs inside and

outside the cloud beore a hailstone comes to the

ground

•

The presence o a large thickness o cloudmass

between the base o the cloud and the le&el o

reeOing o large clouddrops pre&ents the growth o

hailstones by prematurely precipitating out the

(52)

Tornado

•

3 tornado is a mesoscale &iolently>rotating

atmospheric &orte) protruding downward rom

the base o a large cumulonimbus cloud in the

shape o a unnel which oten reaches the ground

with disastrous eBects on lie and property

•

It occurs mostly during passage o a hea&y

thunderstorm or s'uall line o&er a locality

•

"ecause o its unnel shape, it is also sometimes

called a unnel cloud

•

When appearing o&er water, it is called a water

(53)

(54)

(55)

Struktur tornado

• A diameter o ;<<:2<< m, a &ariable depth below the

cloud base with intermittent touch>downs, a life-span &arying rom an hour to se&eral hours, and an erratic path &arying in length rom ; to ;<< kmL

• 7e&ol&ing winds with high positi&e relati&e &orticity and

updrat locally inside the cloud, as ound in a helical &orte)L

• A maximum updraft velocity, ;<<:;0< m=s

• A maximum tangential velocity, ;<<:;0< m=s

• 4)tremely low pressure and high temperature inside the

&ertical columnL

• 4ntrainment o en&ironmental air at e)plosi&e rateL

• 6re'uent lightning Qashes and increasingly thunderous

and roaring sound at the approach o a tornadoL

• #ten hea&y precipitation ollowing the passage o a

(56)

Tornado Circulation and Intensity

• Circulations in a tornado, both horiOontal and &ertical, are sometimes so

strong that they can uproot large trees, bend electric poles, knock down buildings and houses, wipe out crop elds, pick up heavy ob!ects from the ground and throw them around like deadly

pro!ectiles, derail running trains, sink boats and ships plying in

rivers, and occasionally lift boats from river banks and throw them into water, and so on

• There was a report o a tornado which while mo&ing o&er a house in eastern

India picked up a young girl o about ;< years rom the compound o the house and later deposited her saely a ew hundred metres down the path

• 6urther down, it sucked up all the muddy water rom a wide canal ;2 m

deep and deposited it all along its route

• The direction o the circulation and probable speed o the horiOontal and

&ertical components o the wind are usually estimated rom the e)tent and intensity o these damages and destructions

• Casualties to human and animal lie are usually caused by collapse o

poorly>built houses and by their e)posure to hea&y metallic projectiles when e)posed in the open

• In AS3, windspeeds are sometimes estimated on the basis o obser&ed

(57)

(58)