Local to global scale climatic featuresassociated with the floods in Malaysia

in Dec.2006 and Jan.2007

Tetsuzo YASUNARIHydrospheric-Atmospheric Research C

enter, Nagoya University

Collaborators:Hiroshi TAKAHASHI, Hiroki ICHIKAWA,Kunihiko KODERA, Masatake HORI,

Hironari KANAMORI and Hatsuki FUJINAMI

U-wind at 925 hPa (105E-110E,5N-7.5N)V-wind at 925 hPa (105E-110E,5N-7.5N)Rainfall (100E-105E,0-5N)

Rainfall and monsoon surgein Dec.2006 to Jan.2007over southern Malaysia

issues

• Why did these two heavy rainfall events hit for the whole of the Peninsula, rather than to hit the northeast coastal region as usual cold surge cases?

• Why were these two events so abnormally severe, though several cold surge events appeared in this winter monsoon season?

• How were these rainfall events be connected with the anomalous climatic condition of the winter of 2006/2007?

• Will these extreme events tend to occur more frequently in the global warming in the future?

6 Cold surge events over southern SCS during Nov., Dec.2006 and Jan.2007

1 2 3 4 5 6

Strong cold surge with HR/FL over M.P. Weak surge but

HR/FL over MP

Strong surgeHR/Fl over Indonesia

Rainfall amount and mean low-level(925hPa) circulationduring 09Dec.-12Dec. (Case 2)

Typhoon

Tropical Cyclone over Philippine09DEC2006

Typhoon over PhillippinesInduced strong NE-ly windover South China Sea andRainfall in case 2.

6hourly Rainfall at 9-12Dec2006

Wind at 850 hPa

Some strong rainfall over northeast coast of Malay Peninsula.Pronounced offshore rainfall relatedto the diurnal cycle could be observed.over the west of Malay peninsula.

Case 2

Rainfall amount and mean low-level(925hPa) circulationsDuring 17Dec.-20Dec. (Case 3)

6hourly Rainfall at 17-20Dec2006

Wind at 850 hPa

Case 3heavy rainfall over ML

Heavy rainfall due to the stationaryrainfall system appeared around ML.The diurnal cycle could not be observed.

850 ｈ Pa の風と相対渦度（赤線：値は 10 の－ 5 毎に等値線）。青色は、南北風

中緯度からの北風サージに伴い、渦度が輸送される。ボルネオ島とマレー半島の間に、強い渦度がみられる。

2006 年 12 月 15 日 2006 年 12 月 17 日

Meso-scale cloud systems were formed along the strong wind shear and vorticity zones

Rainfall amount and mean low-level(925hPa) circulationsDuring 25Dec.-28Dec. (Case 4)

6hourly Rainfall at 25-28Dec2006

Wind at 850 hPa

Case 4

Rainfall mainly occurred In Sumatra, Java and BorneoIslands.

L

MJO disturbance was passing.

Eastward-propagating large-scale cloud diturbance (called Madden-Julian Oscillation (MJO) from the equatorial Indian Ocean to the western Pacific played a role to control cold surges toward the Malaysian Peninsula.

MJO disturbance from Dec.2006 to Jan. 2007from the equatorial Indian ocean to the western Pacific

(coutesy of T. Nakazawa)Case 3

Case 4

Case 5

2N-6N 　 Average

Case 3:Flood over Malay peninsula → 　 stagnant heavy rainfall

Case 5:Flood over Malay peninsula → gradual eastward shift

Shade –OLR ・・ 220W/m2Contour –Zonal wind (600hPa) ・・ 0m/sColor –3horly rainfall ・・ 0.4,0.6, 0.8,1.0,1.2,1.6,1.8,2,3

Case 4: passage of MJO

MJO

6hourly Rainfall at 6-9Jan2007

Wind at 850 hPa

Case 5: cold surge and MJO

Quasi-two day rainfall within theframework of fixed diurnal cycle

6hourly Rainfall at 11-14Jan2006

Wind at 850 hPa

Case 5heavy rainfall over ML

Heavy rainfall due to the stationaryrainfall system appeared around ML.The diurnal cycle could not be observed.

6hourly Rainfall at 11-14Jan2007

Wind at 850 hPa

Case 5; heavy rainfall over MLDetail version

Heavy rainfall due to the stationaryrainfall system appeared around ML.The diurnal cycle could not be observed.

Wind at 850 hPa

Pronounced steady offshore rainfall in27-28 Jan over Sumatra, Java and Borneo.

Case 66hourly Rainfall at 26-29Jan2007

Large-scale atmospheric circulation associated with heavy rainfall events over southern Malaysia in Dec.17-20

(Case 3)

Time-sequence of Z500

15DEC 16DEC 17DEC

18DEC 19DEC 20DEC

15DEC 16DEC 17DEC

18DEC 19DEC 20DEC

Time-sequence of cold surge (northerly wind at 925hPa) during case 3.

赤道付近で台風が発生した、 2001 年 12 月のケースに、似ている。このときも、長期間北風サージが吹いていた。Chang et al. (2003), GRL.

A similar pattern of persistent cold surge was also seenIn the case of the abnormal Typhoon in Dec. 2001

(C.P. Chang et al., 2003)

８５０ｈＰａ ９２５ｈＰａ

HH

Case 3: Dec.17-21, 2006Strong localized high was formed over south ChinaWhich dirfectly induced strong NE-ly flow to Malaysia

８５０ｈＰａ ９２５ｈＰａ

Case 4: Dec.26-29, 2006Cold surge over East Asia and strong NE-ly over SCSWas connected as NE monsoon (related to MJO forcing?)

８５０ｈＰａ ９２５ｈＰａ

Case 5: Jan.11 – Jan.14, 2007Strong surge in SCS was not connected with cold surge over East Asia.

８５０ｈＰａ ９２５ｈＰａ

Case 6 : Jan.26 - Jan.29, 2007Subtropical high over south China is responsible

for regional strong surge over the South China Sea

HH

Strong surge over the southern SCS is likely to associated with formation of blocking high over

the north Atlantic!

Formation of sub-high over south China associated with wave propagation from N.Atlantic

during Dec. 17-21,2006 (Case 3)

Case 3: Dec.17 － 21 ． 2006

Case 6: Jan.2007 6th pentad

Heavy rainfall in case 3 was associated with sudden warming and strong meridional circulation

in the NH stratosphere

Malaysian rainfall has been changing in the recent years?

Trends of rainfall from 1961 to 2000:boreal winter (DJF)

value =Trend*40years

Climatology* 100 (%)

Endo et al. 2007To be submitted

Blue:increasingRed:decreasing

Interannual variations of seasonal rainfall amount for 16 stations

in the Malaysian Peninsula

Days of heavy rainfall (> 100mm/day) and rainfall amount of the heavy rainy days

（ Dec.-Feb.) at Kota Bahru

Days of heavy rainfall (> 100mm/day) and rainfall amount of the heavy rainy days

（ Dec.-Feb.) at Kuantan

SLP anomaly in Dec.2006Hori and Ueda (2006) GRL

Very similar to the global warmingfuture projection pattern　 !

Dec. 2006

2101-2200 DJFA1B Scenario

1980-2000 Mean

summary• Abnormally heavy rainfall in middle of Dec.2006 (case 3)

and middle of Jan.2007(case5) were due to strong northeasterly surge hit to southern Peninsula with strong cyclonic shear and associated meso-scale cloud systems.

• These strong NE-lies were not necessarily connected with strong cold surges in east Asia (as is usual in NE monsoon surge).

• Eastward-propagating MJO disturbance caused heavy rainfall in Indonesia and Sarawak in the end of Dec./beginning of Jan.(case 4).

• The heavy rainfall in case 3 and 5 were not directly related to the MJO disturbance.

• Localized subtropical high over south China is likely to induce strong surges to the southern peninsula.

• This localized sib-high seemed to be induced by wave-train activity along the subtropical jetstream (~30N) forced presumably by blocking situation over the N. Atlantic.

Summary (continue)• Heavy rainfall & floods in case 3 and 5 have proved to b

e part of anomalous global circulation including the stratosphere.

• Rainfall amount and/or frequency of heavy rainfall events in Malaysia in winter in the past few decades have not shown any increasing (or decreasing) trends, but local pattern of Malaysian rainfall variability and trends are likely to be very sensitive to pattern of large-cale circulation over east and southeast Asia.

• The IPCC prediction of winter monsoon in 2100-2200 has predicted weakening of east Asian winter monsoon, which suggests possible increase of case 3 & 5 type heavy rainfall events (associated with enhanced sub-high over China and north Pacific + warmer surrounding ocean surface.)