69

Extreme Climatic Events in Recent Years andTheir Links to Large-Scale Atmospheric Circulation Features
Shuji YAMAKAWA1* and Ramasamy SUPPIAH2
1

Department of Geosystem Sciences, College of Humanities and Sciences, Nihon University,
3-25-40 Sakurajosui Setagaya-ku, Tokyo 156-8550, Japan
2
CSIRO, Marine and Atmospheric Research, Australia*e-mail: syamaka@chs.nihon-u.ac.jp

Abstract
Impacts and large-scale circulation patterns of recent extreme weather and climatic events in selected
countries are discussed in this paper. Results of detailed analyses of extreme rainfall and snowfall events inJapan and China, impacts of the cyclone “Nargis” on Myanmar and droughts in Australia are given in detail.
Extreme rainfall events in Japan were inferentially associated with strong troposphere warming andstratosphere cooling. The unstable air mass over the northern Pacific and higher sea surface temperatures
also contributed to an intense and extreme rainfall event in Tokyo metropolitan area. A minimum sea ice
area in the Arctic Ocean in the summer of 2007 led to a development of the Arctic low from autumn towinter of 2007/2008 and a southward shift of the Siberian high and heavy snowfalls over Central South
China occurred in the late-January of 2008. Recent droughts of Australia, particularly in 2002-2003 and2006-2007 that caused extensive damage to environment, economy and human life were associated with El
Niño events. These droughts were relatively severer than previous droughts due to an increase in day-timetemperature.
Key words: drought, ENSO, extreme rainfall event, flood tropical cyclone Nargis, heavy snowfall

1. Introduction
In recent years, there have been a series of extreme
climatic events which affected various regions of theworld. The great floods of the Mississippi and Missouri
Rivers in 1993 were among the most costly anddevastating ever to occur in the United States, with $15
billion in damages. The hydrographic basin affected
covered around 1,200 km in length and 700 km in width,
totaling about 840,000 km2. The abnormal climatic
events in 1992-1993 followed the violent eruption of
Mt. Pinatubo in the Philippines on 15 June 1991. In
particular, a cool summer was exhibited in almost theentire mid-latitudes of the northern hemisphere(Yamakawa, 1997).
The other severe flood was the 1998 Yangtze Riverflood. When the waters finally began to subside in
September after the summer monsoon, the Chinese
government reported 3,004 deaths and $20 billion indamages, although the final figures will probably behigher. As winter approached, 14 million people remained homeless. In Japan, severe floods of NiigataFukushima and Fukui Prefectures and many strong
typhoons in 2004 caused serious extensive damage to
agriculture, infrastructure, people and environment.
Global Environmental Research
13/2009: 69-78
printed in Japan

Cyclone “Nargis” that affected Myanmar on 2-3 May
2008 resulted in 133,000 deaths, including the missing(AFP, 17 May 2008). In recent years, excessive snowfalls and extreme rainfall have also caused extensive
damage to crops, environment and human life in China.
Droughts have caused extensive damage to environment,
crop production and economy in Australia during thepast decade. Droughts in 2002-2003 and 2006-2007
have resulted in reduction of more than 50% of wintercrops in Australia. In this paper, we mainly focus
on results from two presentations given during the18th International Congress of Biometeorology, Tokyo(Suppiah, 2008; Yamakawa, 2008). First, we provide
brief summaries of events discussed in this paper.
Second, we attempt to give plausible explanations using
local and large-scale atmospheric and oceanic circulations. Conclusions derived from this study are given at
the end.

2. Extreme Rainfall Events
In this section, we describe three heavy rainfall
events which caused serious damage in Japan. Those
events include, 1) Niigata-Fukushima torrential rain on
13 July 2004, 2) extreme rainfall in Kanazawa and the©2009 AIRIES70

S. YAMAKAWA and R. SUPPIAH

flood event of the Asano River, following the flash flood
event in Kobe, on 28 July 2008, and 3) extreme downpour “The guerrilla downpours” in Tokyo metropolitan
area on 5 August 2008.
1) The torrential rain event that affected the
Niigata-Fukushima region in the north-eastern Central
Japan is linked to large-scale circulation pattern over the
Indian and Pacific Oceans. An intense cumulonimbus(Cb) cloud system in Fig. 1 reveals the moist tongue
penetrated from the Indian Ocean, the South China Sea
and the edge of the North Pacific high.
2) On 28 July 2008, Kanazawa Prefecture, located inCentral Japan along the coast of the Sea of Japan, received 120 mm/h (06:30-07:30) that caused flooding inthat region. Two VIS images revealing cloud patterns of
this event are shown in Fig. 2. The Asano River overflowed for the first time since 1953. After about sevenhours, the Toga River that runs through Kobe, Hyogo
Prefecture in Central western Japan, also caused flash
flood. Five people lost their lives in the flood, whichrose at a rate of 134 cm/12 minutes (14:30-14:42). Basedon MTSAT (Multi-functional Transport Satellite), a
stationary frontal cloud band was identified moving
southward slowly. The former flood was caused directlyby the front, and the latter was triggered due to unstable
air mass on the south of the front. In addition, theserainfall events were associated with warm moist air
from the eastern area of a typhoon0808, which crossed
Taiwan from south-east to north-west direction.
3) The torrential rain event that caused five deaths in
the Tokyo metropolitan region on 5 August 2008 was
one of the severe events which occurred in this century(Fig. 3). This event was triggered with Cb cloudburstthat was associated with a stationary front, a coastal
front and an unstable air mass.

(a)

(ｂ)

Fig. 2 An active Cb band with torrential rains (a) in
Kanazawa at 07JST, and (b) in Kobe at 14JST,
28 July 2008. Typhoon0808 (960 hPa at 09JST)
effected Taiwan and brought moist, warm air toward
the frontal band positioned near the Hokuriku
district. (Source: MTSAT-IR of Kochi Univ.)×

Fig. 1 A satellite image at 06JST, 13 July 2004, when the
Niigata-Fukushima received torrential rains. An active,
extended Cb band, which lay from west to east across theJapanese Archipelago, is seen associated with massive Cu
cloud systems from the Indian Ocean, the South China
Sea, and the western edge of the North Pacific high.
(Source: GOES9-IR of Kochi Univ.)

Fig. 3 “The guerilla-like downpours” due to Cb burst,
which is found at the centre of the area marked with
an ellipse, in Tokyo metropolitan area at 12JST, 5
August 2008. The centre of a subtropical cyclone,marked with a cross, is located to the south and acold vortex to the north. (Source: MTSAT-IR of
Kochi Univ.)

Extreme Climatic Events in Recent Years

The stationary front, which was a vestige from the
Baiu front, stretched from the north-western Pacific tosouthern Kanto District, located in eastern Japan. The
coastal front developed between moist, warm air overTokyo Bay and a north-easterlies stemming from thecold current “Oyashio” which flows off Ibaraki Prefecture, located in eastern Kanto District. The unstable air
mass was the result of combined processes of both
warm, moist air from the east of a subtropical cyclone
located in about 1,000 km to the south of Japan and acold vortex in the Far East, observing a very low temperature of −76°C at 120 hPa (~15 km), which approximately corresponds to the tropopause over Tateno(36°3.3’N，140°7.8’E) at 00Z 4 August 2008. Interestingly, tropospheric warming and stratospheric coolingwere observed globally during this period (IPCC, 2007).
It is possible that these low pressure systems had
associations with a cooling in the stratosphere.

71

heavy snowfalls. The Siberian high with 1,050 hPa(average in January: 1,035 hPa) centred over Mongolia
developed and expanded widely to the south on 25
January 2008. In addition, Fig. 5 shows the presence ofa strong upper level jet stream over the mid-latitudes in
the northern hemisphere and the jet stream was evident
even at the 500 hPa level. The zone corresponded to thesouthern limit of the cold wave extended from Middle
China to the Japanese Archipelago. A stationary deep
trough covered southern Eurasia, and the cold waves
often propagated to East Asia. Moreover, a separate
subtropical anticyclone was formed in the vicinity of
Taiwan (Fig. 4). Due to the clockwise circulation of the
anticyclone, the south-west wind that contained large

HL

3. Heavy Snowfalls in China
The heaviest snowfall in the past 50 years was recorded in Central South China between late January to
mid February 2008, despite marked dry-to-arid conditions observed in recent years. The number of houses
destroyed by this single event reached about 100,000
and the death toll was 133 including the missing (AFP,
24 February 2008). The large-scale circulation pattern at
the 850 hPa level showed a low pressure on the easternedge of the Tibetan plateau and a stationary front extended toward the vicinity of Shanghai at the time ofheavy snowfalls. Isothermal structure during this event
reveals a boundary between rain and snow on the
ground, and it almost corresponds to the position of thefront. Subsequently, the low pressure moved eastward
one after another along this front which resulted inheavy snowfalls with much moisture for six consecutive
days from 25 January in Central South China including
Shanghai.
3.1 Atmospheric Circulation patterns
An examination of streamlines at the 850 hPa level
and cloud systems reveals that a stationary front along
30°N had developed from over the north-eastern Indian
Ocean to the South China Sea, while a high pressure
system was located over the southern East China Sea asshown in Fig. 4. In general, the prevailing north-east
winter monsoon blows from Middle China toward South
China, Southeast Asia, and also towards the Indian
Ocean in January. On the contrary to mean circulation
pattern, at the end of January 2008, a front formed
between extreme cold advection from the strong
Siberian high pressure and warm advection of thosesouth winds on 25 January 2008. A stationary front,
which is the boundary between cold air mass from thenorth and warm air mass from the south, was locatedover Middle China from west to east. A very low surfacepressure region, which formed over the western Sichuan
Province, moved eastward along the front bringing

H

Fig. 4 Air streams over Asia at 00Z, 25 January 2008. Northerly burst from the Siberian cold air mass is clearly seen,
and the convergence of south-westerly and southerly
currents formed the very active moist tongue that caused
heavy snowfalls in Central South China, which ismarked with a dotted circle. (Source: αPlanet K.K. &K. Tahira)Fig. 5 The Arctic vortex and cold vortices of 500 hPa geopotential height (gpm) at 12Z, 25 January 2008. Notemeandering westerlies in the northern hemisphere andthe formation of a deep trough over East Asia, which ismarked with an allipse. (Source: Japan Meteorological
Agency)72

S. YAMAKAWA and R. SUPPIAH

amount of water vapour from the tropical South China
Sea, where the sea surface temperatures (SSTs) arehigher than 25ºC even in winter, dumped a large amountof snow to Central South China. Based on five-day(pentad) averages of sea level pressure (SLP) charts inthe northern hemisphere in Fig. 6. Three salient
characteristics can be noticed in relation to this extreme
weather event. 1) The Siberian high expanded south
toward Central South China with increased centralpressure. 2) The Aleutian low shifted toward north-west,
and also linked with a deeper low pressure centre in the
Arctic Ocean than the average. 3) The wedge-shaped
trough extended from western Siberia to the Middle East

Fig. 6 SLP (hPa) pattern in the last pentad of January 2008. Notea very strong cold low over the Arctic Ocean that is linked
to Icelandic and Aleutian lows. A developed Siberian highexpands toward South China. (Source: Japanese Meteorological Agency)

and prevented the Siberian high from amplification over
Europe. Apart from these, a remarkable development of
massive cumulus (Cu) cloud system was found over thesouth-western part of the Indian Ocean, crossing theequator, in the north-east direction through the
Indo-China Peninsula, Middle and South China to theEast China Sea, the southern coast of Japan and the sea
to the east of Japan. It is probable that this phenomenon
derived from the eastward propagation of the cloudsystem generated over the tropical ocean (Fig. 7) as aresult of Madden-Julian Oscillation (MJO; Madden &Julian, 1971). Moreover, the building-up moistureassociated with the MJO event is likely to be related tothe heavy snowfalls in the Tokyo metropolitan area on 3
February 2008.
SSTs in the tropical Pacific Ocean indicated a La
Niña event with the west-high east-low SST anomalies.
Statistical results also support the view that in the phaseof La Niña the winter pressure pattern is stronger overEast Asia and the cold wave often strikes Japan, and it isindeed true during the winter of 2007/2008 years. The
cold air surges from the Siberian high were replaced byvertical updrafts in the warm pool region around thePhilippine neighbouring waters.
3.2 Effect of decreased sea ice in the Arctic Ocean
The area of the sea ice in the Arctic Ocean, whichshows a decreasing trend during the last 30 years, wasminimized in the summer of 2007 since the beginning of
the satellite observation in 1978. The recorded area of
4,194,000 km2 on 16 September 2007 was the minimum
and approximately 40% less than the lowest area of
7,000,000 km2 in the 1970s and 1980s (JAMSTEC,
2007).
SLP charts in June 2007 showed a west-low, easthigh pressure pattern over the northern Pacific area, sothat southerly winds prevailed around the area between

(m/s)

3

Fig. 7 Distribution of outgoing long-wave radiation (OLR)
anomalies in the late-January of 2008. The propagation of
MJO from the central Indian Ocean toward East Asia isremarkable, indicated by an ellipse. The frontal activity
was very strong along 30°N around the north-western
Pacific. (Source: NOAA web-site)

Fig. 8 Surface wind vector over the northern hemisphere inJune 2007. Prevailing southerlies blew over thenorthern Pacific, because of not only the development of the North Pacific high but also the strong
Siberian low. (Source: NCEP/NCAR reanalyzed
data)Extreme Climatic Events in Recent Years

the Far East and Alaska, as shown in Fig. 8. The
tendency mentioned above was maintained from spring
to early summer in 2007, so the prevailing southerlies
led to an enhancement of Alaska coastal current.
Therefore, some parts of the warm waters flowed into
the Arctic Ocean through the Bering Strait. In thesummer of 2007, a large amount of warmer seawater
appeared in the East Siberian Sea of the Arctic Ocean,and expanded the area of open water that turned out torelease greater sensible and latent heat from the sea surface into the air.
Vertical winds at the 700 hPa level in the northern73

hemisphere in Fig. 9 revealed unusual strong updrafts
during the four-month period from August to Novemberof 2007 over the Arctic Ocean. Consequently, thecontinuation effect of updrafts led to a development of
the Arctic low. Even in January 2008, the Arctic low,
shown in Fig. 6, developed encompassing the area of thenorthern Siberia, which contributed to a southern shiftof the Siberian high, and hence, cold waves and heavy
snowfalls in Central South China. The atmosphericprocesses that led to heavy snowfalls in Middle andSouth China are illustrated in Fig. 10.

4. Tropical Cyclones in the Indian Ocean
Tropical cyclones have significant impacts on environment, infrastructure, economic activities and society
in the tropics. Although tropical cyclones over the northern Indian Ocean develop from May to December, most
severe tropical cyclones of this region were recorded in
May of the pre-monsoon and also from October toDecember of the post-monsoon. Tropical cyclones
formed in this region affect the South Asian region that
includes, India, Bangladesh, Bhutan, Nepal, Myanmar,
Maldives, Pakistan, and Sri Lanka. During the month ofMay, the south-west monsoon sets in, and hence, brings
the rainy season to South Asia. Tropical cyclones anddepressions tend to form on the trough during the monsoon season.
Cyclone “Sidr” which affected Bangladesh on 19
November 2007, resulted in death toll of 4,231. On
average, each year three to four cyclones are formed in
the northern Indian Ocean.
Studies on tropical cyclones over the northern Indian
region (Chu & Wang, 1997; Singh, et al., 2000) revealed(hPa / s)
－0.15
－0.10
－0.05
0.00
＋0.05

Fig. 9 Vertical winds at 700 hPa in the northern hemispherefrom August through November of 2007. Unusual
strong updrafts are seen over the Arctic Ocean. Thiswarming led to a development of the Arctic low.
(Source: NCEP/NCAR re-analyzed data)

Sept. 16, 2007：
Minimum ice area
413km2was recordedon the Arctic
Ocean

Arctic L

AL & SH
moved
Southward.

Siberian H

MJO &clockwise
moist air
moved
NEward.

＊L＊
＊

L

＊
H

North
Pacific
H

In spring &summer of 2007,
lows around theKamchatka
Peninsula
Developed.
⇒ Southerlies
prevailed.
⇒ Warm sea
waters with
10-12℃
moved into the
Arctic Ocean.

MJO

In Jan. & Feb.
of 2008,
heavy snowsin Middle &South China

In Feb. 2008,
on 3：A heavy
snow in Kanto
on 9：A heavy
snow in Kinki

In winter of
2007/08,
ΔSST in thetropical Pacific：
W＋, E－
La Nina：climax
PDO：typical－

Fig. 10 A schematic chart showing the processes that led to heavy snowfalls in Central South
China during late-January of 2008.

74

S. YAMAKAWA and R. SUPPIAH

an increasing trend in recent years. Other studies(Emanuel, 2005; Anthes, et al., 2006; Koltzbach, 2006;
Webster, et al., 2008) suggested a recent increase intropical cyclone number, duration and intensity being
linked to warmer environment. However, Chan (2008)
argued that the recent increase in the occurrence oftropical cyclones is a part of decadal scale variations in
the frequency over the northern Pacific. Whether recent
trends in the frequency occurrence of destructive tropical cyclones are a part of natural variability or due towarming environment, a severe tropical cyclone caused
extensive damage to people, economy and environmentof Myanmar in May 2008. In this section, we will provide favourable synoptic conditions observed before theformation of the tropical cyclone “Nargis” and an account of damage and aftermath of “Nargis.”
4.1 Anomalous circulation patterns around Nargis
On the 2nd of May 2008, a very strong cyclone affected Myanmar (previously called Burma) and caused
extensive damage. On the 27th of April, a tropical depression was formed in the south-western part of the
Bay of Bengal and moved northward, and developed asa cyclone that was classified as category 2 on the 28thof April. The cyclone changed its course to the eastnorth-east on the 29th, and weakened into category 1.
On the 30th, it moved eastward along 16°N. However,the cyclone developed rapidly on the 1st May and,named as “Nargis”, it reached category 4 at 06 UTC the
2nd, with the maximum wind speed of 59 m/sec.
“Nargis” continued to move eastward and landed at 12
UTC in southern Myanmar, comprising the delta of the
Ayeyarwady (Irrawaddy) river, which is a worst course
for the country. After crossing the land it weakened tocategory 3. The spreading cloud associated with thecyclone had a diameter of about 800 km being relatively
compact. The records of the Japan Meteorological

Agency indicated a central minimum pressure value ofthe cyclone of 962 hPa just before its landing.
Streamlines at the 850 hPa level at the time of landing in Fig. 11 show a convergence zone extended fromsouth to north along 110ºE in western China, and thenNargis moved eastward. This convergence zone wasrecognized as the intertropical convergence zone (ITCZ)
around 10°N over the Indian Ocean, via the east side of
the cyclone in the anti-clockwise circulation. The dominant pattern of circulation and the NOAA satellite
images are shown in this figure.
4.2 SST and precipitation patterns for Nargis
Tropical cyclones (typhoons and hurricanes) tend toform over oceanic areas with the SSTs as high as above
26ºC to 27ºC (Ramage, 1971). SSTs over the Bay of
Bengal were favourable for the formation of a cyclone
as shown in Fig. 12. On the weakly mean conditions,from the equatorial region of the Indian Ocean withnegative SST anomalies to the central Bay of Bengal
with normal SSTs (Fig. 13(b)), low-level winds blow
accompanied with massive Cu clouds toward the northern ITCZ. The circulation pattern in the middle troposphere indicates that the southern edge of westerlies
shifted southward near 15°N over the central part of the
Bay of Bengal. As a consequence, “Nargis” moved
slowly eastward. Usually, the southern edge ofwesterlies remains near 25°N along the southern foot of
the Himalayas. On such a condition, the cyclone would
be heading north toward Bangladesh. Furthermore, if
the cyclone had hit northern Myanmar near 18°N, thecyclone would have been weakened rapidly by the(a)Fig. 11 Air streams in and around South Asia at 12Z, 2 May
2008. Over the eastern Indian Ocean, clockwise southerly
winds blew toward Cyclone “Nargis.” On the other hand,westerlies in the middle latitudes shifted southward,
therefore “Nargis” moved toward southern Myanmar.
(Source: α Planet K.K. & K. Tahira)(ｂ)Fig. 12 Distribution of (a) average SST and (b) SST anomalies
in the period from 20 to 26 April 2008. SSTs werenormal over the northern part of the Bay of Bengal andcooler than normal to the south of the Bay.

Extreme Climatic Events in Recent Years

Arakan coastal mountain range located from north tosouth and such a major disaster would not have occurred.
From April to the early May before a monsoon is in fullswing, India is usually hit by pre-monsoon heat waves
as higher SSTs are favourable for the formation of tropical cyclones during this season.
Previous studies (Liebmann et al., 1994: Maloney &Hartmann, 2001; Hall et al., 2001) suggested a link between tropical cyclone formation and the Madden-Julian
Oscillation. The formation and its development of
Nargis were enhanced by the arrival of the MaddenJulian Oscillation described in previous studies as thisoscillation is phase-locked to the seasonal cycle.
The impact of Nargis is very severe due to the rise in
the level of the river derived from the downpours(600 mm in the southeastern part and 500-600 mm in
the southern part and more than 200 mm in a wide areaof Myanmar), and relatively higher level of storm surge
for two days before the new moon associated with hightide. Storm surge and the backflow of the seawater inthe river engulfed so many people who lived in lowlying areas. Furthermore, scanty information for thepeople under the military regime, incomplete breakwater and refuge facilities and the lack of disaster recognition aggravated this catastrophic disaster. The outbreak of cholera, malaria and dengue fever for the rainyseason led to a delay in the reconstruction of theinfrastructure.

5. Droughts
Drought is one of the major hazards affecting
Australia’s landscape, agricultural production, water
resources, human settlement and economy (Manins, etal., 2001). Given the size of Australia, there is little
chance that the whole continent can be affected bydrought at the same time. Drought can end in one part ofthe continent and, at the same time another can begin in
another part. Droughts may last for one season or extend
over several seasons. In this section we provide information about droughts that affected Australia in recent
years. In particular, we focus on 2002-2003 and 20062007 which had severe impacts on various sectors of the

Rainfall (mm)

700

(a)

350

May to October

(b)

300

500
400
300

100
1900

5.1 Rainfall trends
Australian rainfall records from 1900 to 2007 show apositive trend over many parts of the country, except forsouth-western Australia and some parts of coastal
Queensland, Tasmania and southern South Australia(Bureau of Meteorology, 2007). However, during thesecond-half of the century, there has been a stronger
tendency for decreased rainfall in south-western andeastern Australia and increased rainfall over northwestern and central Australia. Such patterns of trends
and their links with the Southern Oscillation Index(SOI) have been reported in previous studies (Suppiah& Hennessy, 1996, 1998; Smith, 2004). Figures 13(a)and 13(b) show rainfall variations over the past century
during wet seasons for northern and southern regions ofAustralia, respectively. The southern Australian wet
season comprises the months May to October with mostrain falling between June and August. The northern
Australian wet season extends from November to April
with most rain falling in the Australian monsoon season(December to February). Seasonal totals show stronger
interannual variability over the last five decades compared to the previous period as shown in Fig. 13(a),particularly for the period November to April.
The lowest ten rainfall years based on all-Australiancontinent, northern and southern wet seasons are shownin Table 1. Reduced rainfall in 1994 and 2002 during thesouthern wet season had severe effects on crops. Widespread and prolonged droughts in the instrumental
record period occurred in 1864-1866, 1880-1886, 18951903, 1911-1916, 1918-1920, 1937-1938, 1940-1941,
1943-1945, 1963-1968, 1972-1973, 1982-1983, 19911995 and 2002-2003. Extended droughts were associated with variations in both atmospheric and oceanic
circulations. In general, the occurrence of droughts inAustralia coincides with El Niño events.

November to April

600

200

country. The costs of drought to government occur
mainly through monetary payments, subsidies to agricultural and industrial sectors and farm family restartschemes. It has become clear that the recent drought
affecting large parts of Australia’s farming regions ismore severe than droughts of the past.

Rainfall (mm)

800

75

1940

1960

Year

1980

200
150
100

Actual rainfall
11-year running means
1920

250

2000

50
1900

Actual rainfall
11-year running means
1920

1940

1960

1980

2000

Year

Fig. 13 (a) Rainfall variations during the northern wet season (May to October) and (b) the southern wet season(November to April) of Australia. (Source: Australian Bureau of Meteorology)

76

S. YAMAKAWA and R. SUPPIAH

Droughts during the first-half of the 1990s and early
2000s mainly affected eastern and northern Australia.
However, one of the worst droughts, since reliable meteorological records began, occurred in 2002-2003. Figure14(a) shows rainfall deficiencies in terms of deciles.
Reduced rainfall during this time was associated with an
El Niño event. The evolution of the El Niño during that
period was clearly evident in zonal wind, thermocline
depth and SST changes over the tropical Pacific. Thisdrought was very severe due to relatively warm temperatures, even though in terms of rainfall it was not
obviously drier than previous droughts. With regard to
the 2002-2003 drought event, Nicholls (2004) reported
that the very high day-time temperatures clearlyreflected the combination of interannual (El Niño)
climate variability and long-term (global) warming and,probably led to the drought being more severe. Rainfall
deciles for the 36 months (1 May 2005 to 30 April 2008)
in Fig. 14(b) also show the presence of drought in eastern Australia (Victoria, New South Wales and southeast
Queensland), and also south-western Western Australia.
Since temperature increases in recent decades have been
attributable to increasing greenhouse gases or anthropogenic activities, increasing intensity of droughts inTable 1 Lowest rainfall amounts recorded in all–
Australian total, northern and southern wet
season during the period from 1900 to 2007.
(Source: Australian Bureau of Meteorology)
All- Australia(Jan. to Dec.)
1902
1905
1961
2002
1994
1935
1965
1928
1919
1938

Northern Wet season(Nov. to Apr.)
1951
1901
1964
1918
2004
1904
1905
1963
1969
1935

(a)

Southern Wet season(May to Oct.)
1994
2002
1982
1940
1902
1946
1967
1928
1944
1937

recent years could also be attributable to human activities (Karoly, et al., 2003).
The occurrence of drought is an integral part of natural variability. However, any future climate change
involving reduced mean rainfall under enhanced greenhouse condition could have significant effects on various sectors of Australian economy as well as the life
style of the population. Recently produced climatechange projections by CSIRO and the Australian Bureauof Meteorology (2007) indicate a tendency toward
reduced rainfall under enhanced greenhouse conditions.
Although projected changes show both increases anddecreases, in most cases rainfall decreases dominate. A
study on the application of Palmer Drought Severity
Index (PDSI) to simulated changes from the CSIRO
MK3 global climate model also suggests an increased
frequency and duration of droughts under enhanced
greenhouse conditions (Mpelasoka, et al., 2007).
5.2 Impacts
In Australia, about two thirds of distributed water
currently goes to agriculture (mainly irrigation) about
10% to households and 10% to water and sewerage services. Deficits in water resources affect cereal crops
such as wheat, barley, etc. the dairy industry, viticulture
and subtropical horticultural industries. It has become
clear that the impact of droughts on Australia’s farming
regions has become much more severe than previous
years. The failure of rainfall in the south in 1994, 2002
and 2006 reduced the agricultural Gross National Product (GDP) by about 30% (ABARE, 2008). Figures 15(a)and 15(b) show winter crop production as a function oftime and rainfall. The effect of reduced rainfall on crops
is clearly evident in these figures. Bushfire risk associated with higher temperatures and lower humidity withstrong winds during drought conditions is a major
hazard. Droughts also have significant impacts on faunaand flora of the country.

(b)Rainfall Decile Ranges

10
8-9
4-7
2-3
1
Australian Rainfall Deciles
1 March 2002 to 31 January 2003

Australian Rainfall Deciles
1 March 2002 to 31 January 2003

Australian Rainfall Deciles
1 May 2005 to 30 April 2008

Fig. 14 (a) Rainfall deciles for the 11-month period (from 1 March 2002 to 31 January 2003) and (b) for the
36-month period (from 1 May 2005 to 30 April 2008). (Source: Australian Bureau of Meteorology)

Extreme Climatic Events in Recent Years
50

45

45

300

40

250

35

200

30
25

Est

150

20
100

15
10
1992

1994

1996

1998

2000

2002

2004

2006

50
2008

Rainfall (mm)40

Crop Production (mn tonnes)

Crop production (mn tonnes)

350
Winter crop production

(a)

77

(b)

35
30
25

Col 3

20

2002
1994

15
10
50

100

2006

150

200

R= 0.62
250

300

350

Rainfall (mm)Year

Fig. 15 (a) Winter crop production of Australia and rainfall during the southern Australian wet season. The crop
production for the year 2007 is an estimated value. (b) The linear relationship between crop production andrainfall, and the three dry years are also shown. Est in Fig. 4 a denotes the estimated value by ABARE.
(Source: ABARE, 2008)

6. Conclusions
Severe extreme rainfall events caused serious extensive damage, for example in Niigata-Fukushima (2004),
Kanazawa and Kobe (2008) regions, Japan. These
events occurred as results of unstable air masses due towarming in the troposphere as well as the cooling in thestratosphere. Some degree of recent warming in the
troposphere and cooling in the stratosphere could belinked to man-made changes during the past century.
The heavy rainfall downpours due to “guerrilla-like”
active convection in the summer of 2008 in Japan was
related to unstable air mass, which was caused byfactors such as frontal Cb band, cold vortices and/or
subtropical cyclones.
A minimum sea ice area in the Arctic Ocean in thesummer of 2007 led to continual updrafts, and hence, adevelopment of the Arctic low from autumn to winter of
2007/2008. In the late-January of 2008, the Arctic low
developed and moved toward Siberia, and then pushed
the Siberian high southward. Such a movement caused
heavy snowfalls in Central South China.
Cyclone Nargis followed an unusual eastward trackin the early-May of 2008 and caused extensive damage
to environment, agriculture, infrastructure, economy,
people of Myanmar. This event was also influenced bydeep meandering of westerlies due to shift of the Arctic
vortex toward the Eurasia Continent (Fig. 11) accompanied by the active Arctic low. In spring through summerof 2008, cold vortices over East Asia and North America
were also associated with the active Arctic low.
Droughts in Australia reflect interannual variabilityof the climate system, which is linked to oceanic andatmospheric fluctuations, such as the El Niño-Southern
Oscillation (ENSO), and high latitude circulation features. Recent droughts in Australia have been more
severe compared to previous droughts. In general,droughts in Australia are associated with the occurrenceof El Niño events. Recent droughts in 1994, 2002 and2006 were no exceptions and were more severe due torelatively warm temperatures, even though in terms ofrainfall these were not obviously drier than previous
droughts. Such an increase in the severity can be
attributable to human activities. Climate change projections also indicate drier conditions which in turn, indicates that droughts in future could be more frequent andmore severe, compared to past events

Acknowledgement
We sincerely thank Prof. Masatoshi Yoshino of theUnited Nations University for continued encouragement
for this study. We thank Prof. Yoshitaka Fukuoka of
Rissho University for useful comments. We also thank
Mr. Kohji Tahira and α planet K.K. for providing
comprehensive weather maps and other materials usedin this analysis.
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Shuji YAMAKAWA
Prof. Dr. Shuji Yamakawa has been with
the Department of Geosystem Science,
Nihon University, Tokyo, Japan, for thelast 9 years and has over 25 years ofexperience in research and teaching on
synoptic climatology and science ofclimate system also in Tukuba University
and Agricultural Environmental Institute.
He received his M. Sc and PhD from theTokyo Metropolitan University. His research interest includes climate
variations and meteorological, climatological disasters in the world,
especially Asia.
He has numerous publications and peer-reviewed
papers on climate system, climate variations and disasters. He is an
Editor of the Journal of Geography, Geographical Review of Japan and
Journal of Agricultural Meteorology.

Ramasamy SUPPIAH
Dr. Ramasamy Suppiah has been with
CSIRO for the last 19 years and has over
25 years of experience in research,teaching and consulting on climate change
and impacts. He received his M. Sc and
PhD from the University of Tsukuba. His
research interest includes climate change,
climate variability and their impacts inAustralian and Asian monsoon regions. He
is currently a Senior Research Scientist in CSIRO, Marine andAtmospheric Research, Melbourne. He has numerous publications that
include peer-reviewed papers on Australian and Asian climate andconsulting reports on climate change impacts. He is an Associate Editor of
the Australian Meteorological Magazine.

(Received 13 January 2009, Accepted 29 February 2009)