Onset Monsun Musim Panas Asia di Semenanjung Indochina

Oleh : Made Dwi Jendra P. (22411313)

ONSET MONSUN PANAS ASIA (ASM)

di SEMENANJUNG INDOCHINA

Merujuk pada paper yang berjudul :

Onset of The Summer Monsoon Over The Indochina Peninsula

: Climatology and Interannual Variation

Yongshemg Zhang, Tim Li, Bin Wang, Guoxiong Wu

Oleh : Made Dwi Jendra P. (22411313)

MATA KULIAH

METEOROLOGI MONSUN

FAKULTAS TEKNIK IL1MU KEBUMIAN

INSTITUT TEKNOLOGI BANDUNG

OUTLINE

1.INTRODUCTION

2.DATASETS

3.DEFINITION OF THE MONSOON ONSET

4.THE CHANGE OF GENERAL CIRCULATION

6/7/2014 Meteorologi Monsun FITB-ITB

4.THE CHANGE OF GENERAL CIRCULATION

ASSOCIATED WITH THE MONSOON ONSET

5.THE INTERANNUAL VARIABILITY OF THE

MONSOON ONSET OVER INDOCHINA

6.CONCLUSIONS

INTRODUCTION


INTRODUCTION


Tahap awal ASIA SUMMER MONSOON (ASM) ditandai oleh pembentukan konveksi yang kuat dan

perubahan arah angin yang terjadi di atas Teluk Benggala, Semenanjung Indocina, dan South China

Sea (SCS) sekitar awal hingga pertengahan bulan mei (Dia et al 1987;. Matsumoto 1992; Murakami,

Matsumoto 1994; Lau dan Yang 1997; Wu dan Zhang 1998; Hsu et al. 1999).

Setelah tahap ini evolusi ASM mengalami beragam arah berhubungan dengan pembentukan subsistem

East Asian Monsoon (EAM) dan South Asian Monsun (SAM)

Tiga cabang arah angin dari sumber yang

berbeda yang mempengaruhi cuaca di

SEMENANJUNG INDOCHINA.

1. The Subtropical westerly from the

Northern Indian subcontinent to the

Indochina Peninsula.

2. The Southeasterly associated with the

subtropical ridge over the western

Pacific


3. The Westerly over the equatorial

eastern indian ocean, which stretches

northeastward in early May as the

Southwesterly flows.

DATASETS


Sumber :

www.worldatlas.com/webimage/countrys/asia/indochina.gif

1. Curah hujan harian rata-rata dari 30

Stasiun di bagian tengah

semenanjung Indochina yang

digunakan untuk membuat Index

curah hujan.

NCAR (1951-1985), CPC of NCEP

(1986-1996), total 46 tahun

2. NCAR – NCEP Reanalyss data, 1948

– 1999


www.worldatlas.com/webimage/countrys/asia/indochina.gif– 1999

3. SST bulanan dari Reynold SST

(Reynolds and Smith 1994), 1950-

1999.

4. Daily OLR dari NOAA, 1979-1996

yang diinterpolasi ulang dengan

(CDC).

DEFINITION


Figure 4 displays the 5-day running mean

climatology

of the rainfall index for 46 years. The wet

season over Indochina is identified from early

May to mid-October while the dry season is

from November to late April. The transition

from a dry to a wet season is characterized

by a sudden increase of the daily rainfall from

2 to 6 mm/day sometime from late April to

mid-May.


Based on the strength and persistence of the rainfall

over Indochina, the onset date for each individual year

is defined as the day on which the 5-day running mean

rainfall index satisfies the following conditions:

1) The amount of the daily rainfall index exceeds 5

mm/day and persists continuously for 5 days;

2) Within the consecutive 20 days, the number of the

days with rainfall greater than 5 mm/day exceeds 10

days.


The mean onset date for the 46 years is 9 May. It is consistent with the

existing results of 10 May and 6–10 May, which were reported by Webster et

al. (1998) and Wang and LinHo (2002), respectively. The earliest onset year is

1988 when the monsoon onset begins on 13 April. The latest year is 1958,

when the monsoon onset begins on 4 June. The standard deviation is 12 days


THE CHANGE OF GENERAL CIRCULATION

ASSOCIATED WITH THE MONSOON ONSET

Berdasarkan data OLR :

H-2 dan H-1 konsentrasi OLR Minimum berada

disekitar diatas Sumatera dan Pasifik bagian

barat. Pada saat ini kondisi di teluk benggala

dan Laut Cina Selatan OLR maksimum.

Pada har “H” OLR minimum konsentrasi

semakin meluas hingga teluk benggala

Pada H+2, konsentrasi OLR semakin meluas


Pada H+2, konsentrasi OLR semakin meluas

yang menandakan konveksi didaerah tersebut

semakin meluas.

Berdasarkan angin 850hpa :

H_2 dan H-1 Strong Westerly, Noerthwestern

India to Southeastern Cina.

Pada hari “H” Westerly jet, Noerthwestern

India to Southeastern Cina melemah.

Westerly diatas equator samudera hindia

meningkat.


Pada H+1 dan H+2, Aliran Soutwesterly di

equator samudera hindia semakin terlihat

jelas.


Berdasarkan tes The Peak of The

power spectrum 12 -25 days

aktifitas ISO berkaitan erat

dengan onset Monset.

Wet Phase berkaitan dengan

Anomalous Southerly flow and


Onset monsun In phase with the

westward propagation of positive

vorticity and that Low OLR

originated Over Scs and the

western Pacific.

Anomalous Southerly flow and

Dry Phase concorrent with

Anomalous Northerly flow

Selama periode Onset (0-(+4)) ;

Ada penyimpangan progasi

cyclone kearah barat dari SCS

(Laut Cina Selatan)

6-2 hari sebeleum onset monsun

anticyclone bergerak melewati

sekitar indochina


Ketika cyclone tiba di pantai barat

semenanjung indochina

southerlies kuat berhembus

kesana.

Anticyclone mencerminkan ISO

Propagasi ke arah barat equatorial

Rossby waves.

Propagasi ke arah barat jelas

terlihat dari vertical velocity

composite 700 hpa.

Bergerak melewati SCS,

Indochina, Teluk benggala dan

akhirnya mencapai The Indian

subcontinent.


THE INTERANNUAL VARIABILITY OF


THE INTERANNUAL VARIABILITY OF

THE MONSOON ONSET OVER INDOCHINA

1

2


Dalam riset ini menggunakan SSTA (Anomali suhu muka laut) dari

dua daerah disekitar samudera pasifik. Pertama daerah nino 3,

seperti gambar diatas, kedua daerah western pasifik pada posisi

10⁰-20⁰ N, 135⁰-165⁰E


The climatological mean rainfall amount is 360 mm and the variance is 62 mm.

For the 11 wettest years with anomalous rainfall exceeding 50 mm (0.8

std dev), there are 8 early onset years (the monsoon onsets before 9 May). For

the 10 driest years with rainfall anomaly less than 250 mm, there are 9 late

onset years (the monsoon onsets after 9 May). Thus, during the developing stage

(May–June) of the summer monsoon, a wet year is usually concurrent with an

early onset while a dry year is with a late onset.


Untuk onset monsun yang lebih awal

The COLD SSTA cenderung bertahan dari

musim dingin sebelumnya sampai

musim dingin berikutnya.

Untuk onset monsun yang terlambat

The WARM SSTA cenderung bertahan

dari musim semi sebelumnya sampai

musim dingin berikutnya.


Untuk onset monsun yang lebih awal

The WARM SSTA cenderung bertahan

melewati seluruh tahun.

Untuk tahun onset terlambat, 10 tahun dingin

diidentifikasi pada musim dingin sebelumnya

sementara hanya 8 tahun dingin ditemukan baik di

musim semi terlambat dan musim dingin, berikut

menunjukkan bahwa hubungan antara onset

monsoon dengan Pasifik Barat SSTA tidak kuat

kecuali dalam musim dingin sebelumnya.

Dalam 14 tahun Onset monsun lebih awal

didalamnya terdapat 7 La Nina, 5 Fase

berkembang 2 fase Punah.onset monsun

yang lebih awal The WARM SSTA cenderung

bertahan melewati seluruh tahun.

Dalam 15 tahun Onset Monsun terlambat

terdapat 8 El Nino, 5 fase berkembang 3 fase

punah.

the bimonthly early-minus-late. SST

composites from the preceding December–

January through April–May. The SST


January through April–May. The SST

anomalies exhibit a clear El Nino pattern in

the tropical Pacific Ocean. In the preceding

winter, cold SST anomalies are identified in

the central Pacific while the warm SST

anomalies occur in the western Pacific. During

spring, the cold SST

anomalies increase in the central-eastern

Pacific while the warm SST anomalies persist

in the western Pacific.

Figure 15 shows the early-minus-late

composites of the surface wind.

Corresponding to the SST anomalies in the

Pacific Ocean, the anomalous easterlies

appear across the equatorial Pacific Ocean

and persist from the

preceding winter to spring. In the Indian

Ocean, the anomalous southwesterlies

occur in the northeastern Indian Ocean in

the preceding winter [DJ(-1) and

FM(0)], and extend westward to the


FM(0)], and extend westward to the

western coast of the Indochina Peninsula in

the late spring [AM(0)]. The appearance of

the anomalous westerlies in the Indian

Ocean and easterlies in the equatorial

Pacific exhibits

The appearance of the anomalous

westerlies in the Indian Ocean and

easterlies in the equatorial Pacific exhibits

an overturning of the Walker circulation

associated withENSO

Fig. 16. A minimum OLR center, as the proxy

for the increase of tropical convective

activities, appears over the southern SCS and

the southern Indochina Peninsula during the

preceding winter and spring. Meanwhile,

a maximum OLR center is located in the

central

Pacific. Consistent with the anomalous wind

fields, these two anomalous OLR centers

reflect the overturning of the Walker

circulation. The southern Indian Ocean is


circulation. The southern Indian Ocean is

under the control of the positive OLR

anomalies with a maximum center over the

southeastern region (58–208S, 1008–1208E)

in the late spring [AM(0)].

The western Pacific subtropical high (WPSH) is an

important system regulating the weather and

climate regimes over Southeast Asia (Chang et al.

2000a,b). Its variations in the early/late onset years

are presented in

Fig. 17, which outlines the 5860- and 5865-m

contours of 500-hPa height, respectively. These two

contours are chosen because they describe the

characteristics of the

subtropical ridge. The strength and shape of WPSH

between the early and late monsoon onset

composites differ remarkably. The early onset is


composites differ remarkably. The early onset is

preceded by a weakening and eastward withdrawal

of the subtropical ridge.

For the late onset composite, the subtropical ridge

controls the entire SCS and the southern part of the

Indochina Peninsula. The weakening and eastward

shift of the WPSH is favorable for the enhanced

rising motion

and strong convection over the Indochina

Peninsula, while the strong WPSH leads to the

suppressed convective activities.

CONCLUSIONS


CONCLUSIONS

1. Berdasarkan Data Klimatologi onset Monsoon di Semenanjung Indochina

tanggal 9 Mei. Onset monset setiap tahunnya sangat bervariasi antara

Pertengah April hingga awal Juni. Onset monsun ditandai dengan meluasnya

konveksi diatas daerah Sumatera hingga menuju utara, pergerakan angin tropis

baratdaya menuju Pantai Barat wilayah Indochina dan intensifikasi INDIA-

BURMA trough di ketinggian 500-hpa.

2. Osilasi intraseasonal (ISO) dengan skala waktu dominan 12 – 25 hari, sangat

berkaitan erat dengan waktu dari Onset Monsoon . Hal ini berasal dari

SCS (Laut Cina Selatan) dan Pasifik barat kemudian menyebar ke arah barat

menuju Semenanjung Indocina.


menuju Semenanjung Indocina.

3. Ada kaitan yang erat antara awal atau terlambatnya onset monsun dengan

kondisi anomali SST (dingin/hangat) di Perairan Barat Pasifik dan Perairan

Timur tengah Pasifik selama musim semi di Belahan Bumi Utara

4. Berdasarkan Komposit SST Early minus Late, onset monsun lebih awal akibat

pemanasan convektif yang kuat di selatan indochina dan selatan SCS

mendahului musim dingin dan musim semi. Hal ini sangat berkaitan dengan

perubahan sirkulasi Walker dan Sirkulasi Hadley secara lokal.

Onset Monsun Musim Panas Asia di Semenanjung Indochina

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