No. 28

Spring 2012
ContentsPage

El Niño Outlook (April – October 2012)

1

JM A’s Seasonal Numerical Ensemble Prediction for Summer 20122

Warm Season Outlook for Summer 2012 in Japan

4

Asian Winter Monsoon Summary for 2011/2012

5

JM A’s Advisory Panel on Extreme Climate Events

12

Participation of TCC Experts in RCOFs and Expert Visits to NMHSs in Southeast Asia

13

El Niño Outlook (April – October 2012)
It is likely that neutral conditions will continue throughout the Northern Hemisphere summer.

activity was above normal over and around Indonesia.
Over the western equatorial Pacific, easterly winds in thelower troposphere were stronger than normal in early
March and weaker than normal in late March.
According to JMA's El Niño prediction model, theNINO.3 SST will be normal in the Northern Hemispherespring and above normal in summer (Figure 4). Although
the development of El Niño conditions in summer is possible, the uncertainty of the prediction is large for thesummer and beyond. Considering the bias characteristicsof the prediction, it is more likely that ENSO-neutral conditions will persist throughout the summer.

El Niño/La Niña
In March 2012, the NINO.3 SST deviation was -0.2°C.
SSTs in the equatorial Pacific were below normal mainlyin the central part, while above-normal values were observed in the eastern part (Figures 1 and 3 (a)). Positive
subsurface temperature anomalies were maintained in thewestern equatorial Pacific, while negative values in theeastern part almost disappeared (Figures 2 and 3 (b)).
These oceanic characteristics indicate the persistence of
ENSO-neutral conditions. In the atmosphere, convective
(a)

(a)

(b)

(b)

Figure 1 Monthly mean (a) sea surface temperatures(SSTs) and (b) SST anomalies in the Indian and Pacific
Ocean areas for March 2012
Contour intervals are 1˚C in (a) and 0.5˚C in (b). The base period for the normal is 1981 – 2010.

TCC News

Figure 2 Monthly mean depth-longitude cross sections of(a) temperatures and (b) temperature anomalies in theequatorial Indian and Pacific Ocean areas for March 2012
Contour intervals are 1˚C in (a) and 0.5˚C in (b). The baseperiod for the normal is 1981 – 2010.

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No. 28 | Spring 2012

(a)

(b)

Figure 3 Time-longitude cross sections of (a) SST and (b) ocean heat content (OHC) anomalies along the equatorin the Indian and Pacific Ocean areas
OHCs are defined here as vertical averaged temperatures in the top 300m. The base period for the normal is 1981 – 2010.

Western Pacific and Indian Ocean
The SST in the tropical western Pacific (NINO.WEST)
region was near normal in March, and is likely to be nearnormal throughout the Northern Hemisphere summer.
The SST in the tropical Indian Ocean (IOBW) region
was below normal in March. It is likely to gradually approach a normal level over the coming months, and will
be near normal in the Northern Hemisphere summer.
(Ichiro Ishikawa, Climate Prediction Division)* The SST normals for the NINO.WEST region (Eq. –15°N, 130°E – 150°E) and the IOBW region (20°S –20°N, 40°E – 100°E) are defined as linear extrapolations
with respect to a sliding 30-year period in order to remove
the effects of long-term trends.

Figure 4 Outlook of the NINO.3 SST deviation produced by the El Niño prediction modelThis figure shows a time series of the monthly NINO.3 SST
deviations. The thick line with closed circles shows observed SST deviations, and the boxes show the values produced for the next six months by the El Niño prediction
model. Each box denotes the range into which the SST
deviation is expected to fall with a probability of 70%.

JMA’s Seasonal Numerical Ensemble Prediction for Summer 2012
According to JMA’s seasonal numerical prediction model, sea surface temperature (SST) anomalies in the easternequatorial Pacific will be above normal this summer, suggesting a transition to El Niño-like conditions. In line withthis prediction, active convection in the central equatorial
Pacific and a southward shift of the sub-tropical jet are expected. However, as prediction skill in relation to El Niño/La
Niña conditions from spring through summer is relatively
low at the end of La Niña periods, it should be noted thatthe extent of atmospheric influence from the predicted El
Niño-like SST anomalies is uncertain. Conversely, active
convection to the east of the Philippines and inactive convection over the Maritime Continent and the northern part of
the Indian Ocean are predicted.

TCC News

2

1. Introduction
This article outlines JMA’s dynamical seasonal ensemble prediction for summer (June – August) 2012, which
was used as a basis for the Agency’s operational
warm-season outlook issued on 25 April 2012. This prediction is based on the seasonal ensemble prediction system used in conjunction with the Atmosphere-Ocean
General Circulation Model (AOGCM). Please refer to theseparate column for details of the system.
Section 2 outlines the global SST anomaly predictions,and Section 3 describes the circulation fields expected
over the tropics and sub-tropics in association with theseanomalies. Finally, the circulation fields predicted for themid- and high latitudes of the Northern Hemisphere are
explained in Section 4.

No. 28 | Spring 2012

2. SST anomalies (Figure 5)
The predicted SST anomalies are shown in Figure 5.
Above-normal values are expected in the eastern equatorial Pacific, suggesting a transition to El Niño-like conditions. However, hindcast experimentation indicates that
JMA’s model tends to predict a quicker transition to El
Niño conditions and that the prediction skill for El Niño/La Niña conditions from spring through summer isrelatively low at the end of La Niña periods. Accordingly,
JMA’s
El
Niño
Outlook(http://ds.data.jma.go.jp/tcc/tcc/products/elnino/outlook.html) predicts that ENSO-neutral conditions are likely tocontinue during the summer. Meanwhile, above-normal
SSTs are expected in the western tropical Pacific despite
the predicted El Niño-like SST anomalies. In the tropicalIndian Ocean, near-normal SSTs are predicted.

SST

Figure 5 Predicted SSTs (contours) and SST anomalies(shading) for June – August 2012 (ensemble mean of 51
members)

3. Prediction for the tropics and sub-tropics (Figure 6)
Above-normal precipitation is predicted (a) from thecentral to the eastern equatorial Pacific and (b) to the eastof the Philippines. Considering the uncertainty of the prediction for a transition to El Niño-like conditions, theabove-normal precipitation prediction in (a) should beinterpreted with caution. However, that in (b) can be reasonably expected in response to high SSTs over the western tropical Pacific. Below-normal precipitation is expected over the Maritime Continent and the northern partof the Indian Ocean.
In the upper troposphere, a negative-velocity (i.e., moredivergent) potential anomaly at 200 hPa is predicted over
the tropical Pacific, while positive (i.e., more convergent)anomalies are expected over the tropical Indian Ocean,reflecting the precipitation anomaly patterns in the tropics.

The stream function at 200 hPa is generally expected tobe negative in the Northern Hemisphere, reflecting thezonal pattern of precipitation (i.e., active near the equatorand inactive with increasing distance from it). This indicates a southward-shifting tendency for the sub-tropicaljet. However, considering that these anomaly patterns may
reflect the predicted El Niño-like SST anomalies, theyshould be interpreted with caution. Positive (i.e., anti-cyclonic) anomalies are expected to the east of thePhilippines, reflecting above-normal precipitation in theregion.
Stream function anomalies at 850 hPa are expected tobe negative (i.e., cyclonic) to the east of the Philippines,
suggesting development of the monsoon trough in theregion. Meanwhile, positive (i.e., anti-cyclonic) anomalies
are expected over the eastern part of the Indian Ocean,reflecting inactive convection in the region.

(a)RAIN(a)RAIN(c)PSI200(c)PSI200(b)CHI200(b)CHI200(d)PSI850(d)PSI850

Figure 6 Predicted atmospheric fields from 60°N – 60°S for June – August 2012 (ensemble mean of 51 members)(a) Precipitation (contours) and anomaly (shading). The contour interval is 2 mm/day.
(b) Velocity potential at 200 hPa (contours) and anomaly (shading). The contour interval is 2 × 10 6 m2/s.
(c) Stream function at 200 hPa (contours) and anomaly (shading). The contour interval is 16 × 106 m2/s.
(d) Stream function at 850 hPa (contours) and anomaly (shading). The contour interval is 5 × 10 6 m2/s.

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No. 28 | Spring 2012

(a)SLP(a)SLP(b)Z500(b)Z500

4. Prediction for the mid- and high latitudes of theNorthern Hemisphere (Figure 7)
Negative anomalies of sea level pressure are predicted in most regions of the North Pacific High.
However, positive anomalies are expected only in thewestern part in association with active convection to
the east of the Philippines. Geo-potential heightanomalies at 500 hPa are expected to be positive overalmost the whole of the Northern Hemisphere, reflecting the influence of the recent warming trend.
-16 -12 -16-8 -12-4 -80 -44 0 8 412 816 12

16-120 -90-120-60-90-30-600 -3030 0 60 3090 60
12090 120

Figures 7 Predicted atmospheric fields from 20°N – 90°N
for June – August 2012 (ensemble mean of 51 members)(a) Sea level pressure (contours) and anomaly (shading). The
contour interval is 4 hPa.
(b) 500 hPa height (contours) and anomaly (shading). The contour interval is 60 m.

(Masayuki Hirai, Climate Prediction Division)

JMA’s Seasonal Ensemble Prediction System
JMA operates a seasonal Ensemble Prediction System (EPS) using the Atmosphere-Ocean General Circulation Model (AOGCM)
to make seasonal predictions beyond a one-month time range. The EPS produces perturbed initial conditions by means of a combination of the initial perturbation method and the lagged average forecasting (LAF) method. The prediction is made using 51
members from the latest six initial dates (nine members are run every five days). Details of the prediction system and verification
maps based on 30-year hindcast experiments (1979 – 2008) are available at http://ds.data.jma.go.jp/tcc/tcc/products/model/.

Warm Season Outlook for Summer 2012 in JapanFor summer 2012, mean temperatures are likely to benear normal or above normal, both with 40% probability, inwestern Japan and Okinawa/Amami. No particular characteristics are expected in terms of warm-season precipitation
amounts in any region.

2. Outlook background
JMA’s coupled global circulation model predicts that
SST anomalies averaged over the NINO.3 region will be
above normal in summer 2012. However, the prediction
accuracy of NINO.3’s SST in summer is relatively low
around the end of La Niña periods in spring. Accordingly,
it is considered that SST anomalies in NINO.3 will bemostly near normal this summer. SSTs in the tropical Indian Ocean (IOBW) and in the western equatorial Pacificare both expected to be near normal in summer 2012.
Three-month precipitation anomalies are predicted to
be above normal over central and eastern parts of theequatorial Pacific, and atmospheric circulation anomaly
patterns over the tropical and sub-tropical Pacific are predicted to be similar to those seen during El Niño periods.
Moreover, 850-hPa temperatures over northern Japan are
predicted to be lower than those of the climatic normal.
As such anomalous patterns are considered to appear due
to predicted El Niño-like SST anomalies, the predictions
should be treated with caution.
Conversely, as positive anomalies of three-month precipitation around the Philippines are predicted, it is con-

1. Outlook summary
JMA issued its outlook in relation to the area over Japan for the coming summer in February, and updated it inMarch and April. For summer 2012, mean temperatures
are likely to be near normal or above normal, both with
40% probability, in western Japan and Okinawa/Amami.
No particular characteristics are expected during the warm
season or the rainy season (Baiu) in terms of precipitation
amounts in any region (Figures 8 and 9).

NorthernJapan

WesternJapan

EasternJapan

Okinawa/Amami

Category－0+

Northern Japan

30

40

30

Eastern Japan

30

30

40

Western Japan

20

40

40

Okinawa and Amami

20

40

40

(Category －: below normal, 0 : normal, + : above normal, Unit : %)Figure 8

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Outlook for summer 2012 temperature probability in Japan4

No. 28 | Spring 2012

sidered that the extension of the North Pacific high will bealmost normal around Japan during the summer in spite of
the predicted El Niño-like SST anomalies. The TibetanHigh is also expected to be normal. These results indicatethat the circulation pattern around Japan will be almost
normal in summer.
However, 500-hPa height anomalies are predicted to bepositive over almost the whole of the Northern Hemisphere due to the influence of the recent warm trend. Furthermore, a tendency for above-normal temperatures has
been observed in all regions over the last 10 years, indicating that this summer-averaged temperature tends to be

above normal in Japan.
In terms of atmospheric circulation around Japan, theintensities of the North Pacific High and the Tibetan Highare expected to be almost normal. However, due to the
influence of the recent warm trend, temperatures are expected to be above normal nationwide. As for temperatures in northern and eastern Japan, the probability ofabove-normal values is reduced to a certain extent in consideration of the possibility of El Niño-like SST patterns.
(Takafumi Umeda, Climate Prediction Division)

－

0

+

Sea of Japan side

30

40

30

Pacific side

30

40

30

Sea of Japan side

30

40

30

Pacific side

30

40

30

Sea of Japan side

30

40

30

Pacific side

30

40

30

30

40

30

Category
Northern Japan
Sea of Japan side
Northern Japan
Pacific side

Eastern Japan
Sea of Japan side
Western Japan
Sea of Japan side

Northern Japan

Eastern Japan
Eastern Japan
Pacific side
Western Japan
Pacific side

Western Japan

Okinawa and Amami
Okinawa/Amami(Category －: below normal, 0 : normal, + : above normal, Unit : %)Figure 9

Outlook for summer 2012 precipitation probability in Japan

Asian Winter Monsoon Summary for 2011/2012
Many parts of East and Central Asia experienced significantly below-normal temperatures throughout winter (December – February) 2011/2012. This report summarizes therelated surface climate characteristics, atmospheric circulation and primary factors contributing to the cold conditions
observed. The relevant factors were clarified based on investigation by JMA’s Advisory Panel on Extreme Climate
Events. (For details of the panel, see the related article on
page 12.)high temperatures were seen from northern Central Siberia to northern Western Siberia. In January, extremely low
temperatures were observed around Mongolia, and extremely light precipitation amounts (snow) were seenfrom the southern part of Western Siberia to Kazakhstan.
In February, extremely low temperatures were observed
from central Mongolia to the Middle East, while extremely high temperatures were seen from northern Central Siberia to northern Western Siberia. Extremely light
precipitation (snow) amounts were observed from Western Siberia to northern Kazakhstan.

Note: JRA/JCDAS (Onogi et al. 2007) atmospheric circulation data and COBE-SST (JMA 2006) sea surface temperature (SST)/sea ice concentration data were used forthis investigation. The outgoing longwave radiation(OLR) data referenced to infer tropical convective activity
were originally provided by NOAA. The base period forthe normal is 1981 – 2010.
1. Surface climate conditions
In winter 2011/2012, Asian countries in the
mid-latitudes experienced significantly lower-than-normal
temperatures due to strong cold-air inflow, while thenorthern part of Siberia and southern Asian countries experienced higher-than-normal temperatures (Figure 10).
Figure 11 shows extreme climate events that occurredfrom December 2011 to February 2012. In December
2011, extremely low temperatures were observed in eastern Mongolia and southern Central Asia, while extremely

TCC News

Figure 10 Seasonal temperature anomalies for winter(December – February) 2011/2012
Anomalies are deviations from the normal (i.e., the 1981 –2010 average). The contour interval is 1°C.

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No. 28 | Spring 2012

December 2011

Figure 11

January 2012

February 2012

Extreme climate events from December 2011 to February 2012

2. Characteristic atmospheric circulation causing thecold winter conditions
In the 500-hPa height field for boreal winter 2011/2012(Figure 12 (a)), distinct wave trains were observed fromthe North Atlantic to Eurasia with positive anomalies overwestern Siberia and negative anomalies over northeastern
Asia, indicating significant meandering of the polar front
jet stream. This wavy pattern persisted throughout the
winter (Figure 13), forming in association with stationary
Rossby wave packets propagating eastward from the North
Atlantic (Figure 14).
In the sea level pressure field (Figure 12 (b)), positive
anomalies were seen across northern Eurasia, and especially over western Siberia. The Siberian High was significantly enhanced and expanded, reaching its strongest level
since 1979/1980 (Figure 15). The intensification of the(a) Z500

Siberian High was associated with upper-level ridges overwestern Siberia (Takaya and Nakamura 2005a and 2005b)(Figure 16). The enhanced Siberian High contributed to an
intensification of the East Asian winter monsoon, whichstrengthened cold air advection over the region.
In the 850-hPa temperature field (Figure 12 (c)), negative anomalies were seen in the mid-latitudes of Eurasia,
especially over Central and East Asia. In the lower troposphere, anticyclonic circulation anomalies centered overwestern Siberia brought a cold air mass from central andeastern Siberia to Central Asia and Mongolia, contributing
to extremely below-normal temperatures in the latter areas
and enhancing the Siberian High (Figure 17).
Anticyclonic circulation anomalies over western Siberia
were associated with the upper-level blocking ridges
there.

(b) SLP(c) T850(Teruko Manabe, Tokyo Climate Center)

Figure 12 Three-month mean (a) 500-hPa height, (b) sea level pressure and (c) 850-hPa temperature for
December 2011 – February 2012
The contour intervals are (a) 60 m, (b) 4 hPa and (c) 4˚C. The shading indicates respective anomalies (i.e., deviations from the 1981 – 2010 average). Contours/shading are not shown for areas with altitudes exceeding 1,600 m.
(b) January 2012(a) December 2011(c) February 2012

Figure 13 Monthly mean 500-hPa height for (a) December 2011, (b) January 2012 and (c) February 2012
The contour intervals are 60 m, and the shading indicates 500-hPa height anomalies.

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No. 28 | Spring 2012

In the upper troposphere, Rossby wave packets propagated eastward from southern China to the area east ofJapan (Figure 14). Distinct anticyclonic circulation anomalies were seen over the former area and cyclonic circulation anomalies were observed over the latter. In line withthese conditions, northerly wind anomalies were seen overJapan, indicating a southward meandering of the subtropical jet stream around the country (Figure 18). In associa-

tion, upper-level cold air frequently moved into Japan,
contributing to below-normal temperatures over the country and heavy snowfall on its Sea of Japan side.
In the zonally averaged fields over the mid-latitudes
from central to eastern Eurasia, temperatures were below
normal throughout the whole of the troposphere, andgeopotential heights were below and above normal in theupper and lower troposphere, respectively (Figure 19).
hPa

15 m2/s2

x 106 m2/s

Figure 14 Three-month mean 200-hPa stream function anomalies
and wave activity flux for December 2011 – February 2012
The contours and shading indicate stream function anomalies at intervals of 3 × 106 m2/s. The warm- (cold)-color shading denotes
anticyclonic (cyclonic) circulation anomalies in the Northern Hemisphere, and vice versa in the Southern Hemisphere. The vectors show
wave activity flux (unit: m2/s2) based on Takaya and Nakamura (2001).
hPa

Figure 15 Interannual variation of area-averaged sea levelpressure anomalies (unit: hPa) around the center of theSiberian High (40˚N – 60˚N, 80˚E – 120˚E) for winters (December – February) from 1979/1980 to 2011/2012

m

m/s
℃

Figure 16 Time series of area-averaged sea level pressureanomalies around the center of the Siberian High (40˚N –60˚N, 80˚E – 120˚E) and area-averaged 500-hPa height anomalies over western Siberia (50˚N – 70˚N, 60˚E – 90˚E) from 16
November 2011 to 15 March 2012
The black and red lines indicate five-day running mean values ofarea-averaged sea level pressure anomalies (unit: hPa) and
500-hPa height anomalies (unit: m), respectively. The coefficientof correlation between them for the period from 1 December,
2011, to 29 February, 2012, is 0.60 (with a 95% confidence level).

Figure 17 Three-month mean 850-hPa wind vector
anomalies and 850-hPa normal temperatures for December 2011 – February 2012
The vectors indicate wind vector anomalies (unit: m/s), andthe shading denotes normal temperatures (unit: ˚C; 1981 –2010 average).
50˚E – 120˚E

m/s

˚C

Figure 18 Three-month mean 200-hPa stream function
anomalies and meridional wind anomalies for December
2011 – February 2012
The contours denote stream function anomalies at intervals of 3
× 106 m2/s. The shading indicates meridional wind anomalies(unit: m/s), and positive (warm-color) and negative (cold-color)
values denote southerly (northerly) wind anomalies, respectively.

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Figure 19 Latitude-height cross section of three-monthmean geopotential height anomalies and temperature
anomalies zonally averaged between 50˚E – 120˚E for
December 2011 – February 2012
The contours denote geopotential height anomalies at intervals of 20 m. The shading indicates temperature anomalies (unit: ˚C).

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No. 28 | Spring 2012

3. Primary factors℃

3.1 Southward meandering of the subtropical jet
stream around Japan
In winter 2011/2012, SST anomaly patterns in the Pacific exhibited La Niña-like conditions* (Figure 20 (a)),
and convective activity was enhanced around the Maritime Continent throughout the season (Figure 20 (b)). It
can be inferred that this active convection led to the upper-level anticyclonic circulation anomalies seen aroundsouthern China by forcing a Gill-type response (Gill1980) (Figure 20 (b)). These anomaly patterns in convective activity and atmospheric circulation are typical ofpast La Niña events (Figure 21). Accordingly, the southward meandering of the subtropical jet stream around
Japan, which caused frequent cold air flows over thecountry, was considered to be associated with the La Niña-like conditions.

(a)

(b)
W/m 2

* JMA defines a La Niña event as a phenomenon inwhich the five-month running-mean values of monthly
SST deviations from the sliding 30-year mean for the El
Niño monitoring region (NINO.3: 5˚S – 5˚N, 150˚W –90˚W) stay at -0.5˚C or below for six consecutive months
or longer. As SST values remained below -0.5˚C for only
five consecutive months from September 2011 to January
2012, the criteria for JMA’s La Niña definition were notmet.

Figure 20 Three-month mean (a) sea surface temperature (SST) anomalies and (b) 200-hPa stream function
anomalies and outgoing longwave radiation (OLR) anomalies for December 2011 – February 2012(a) The contours and shading indicate SST anomalies at intervals of 0.5˚C. (b) The contours denote stream function
anomalies at intervals of 3 × 106 m2/s, and the shading indicates OLR anomalies (unit: W/m2). The cold- (warm-) color
shading denotes enhanced (suppressed) convective activity.

(b)

(a)

Figure 21 La Niña composites of three-month mean (a) outgoing longwave radiation (OLR) anomalies and (b) 200-hPa
stream function anomalies for December – February(a) The contours indicate OLR anomalies at intervals of 4 W/m2 (shown between -20 W/m2 and 20 W/m2). (b) The contours denotestream function anomalies at intervals of 3 × 106 m2/s. (a) and (b) The past La Niña winters (December – February) selected for thecomposites are those of 1984/1985, 1988/1989, 1995/1996, 1998/1999, 1999/2000, 2005/2006 and 2007/2008. The gray shading
indicates a 95% confidence level as indicated by t-testing.

3.2 Significant meandering of the polar front jet stream
over Eurasia
The wave trains along the polar jet stream over Eurasiathat contributed to the intensification and northwestward
expansion of the Siberian High mainly originated in the
North Atlantic, where upper-level cyclonic andanticyclonic circulation anomalies were seen over subtropical and mid-latitude areas, respectively (Figure 14).
In past La Niña events (Figure 21), anticyclonic circulation anomalies tended to appear across the middle latitudes
from the eastern North Pacific to the North Atlantic withthree centers west of the USA, over southeastern parts ofthe country, and west of Europe. Related circulation
anomalies for winter 2011/2012 (Figure 14) showedanomaly patterns typical of past events. Thus, La Niña-like
conditions may be associated with the anticyclonic circulation anomalies observed in the North Atlantic
mid-latitudes.

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Significant divergence anomalies in the upper troposphere were seen around northern South America and thetropical North Atlantic in association with the enhanced
convective activity observed there (Figure 22). Anomalous
northward-flowing divergent winds seen on the northernside of the divergence converged over areas east of the
Caribbean Sea where the Rossby wave source(Sardeshmukh and Hoskins 1988) exhibited positive values(indicating vorticity sources) (Figure 23). Active convection around northern South America and the tropical North
Atlantic was therefore considered responsible for the generation of upper-level cyclonic circulation anomalies as an
origin of the wave trains seen over the subtropical North
Atlantic.
Active convection around northern South America andthe tropical North Atlantic was also seen in past La Niña
events (Figure 21 (a)). SSTs were above normal in northwestern parts of the tropical North Atlantic and signifi-

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No. 28 | Spring 2012

cantly below normal in the tropical South Atlantic (Figure 20). Statistical analysis shows that convective activity over tropical areas tends to be enhanced when tropical SSTs are below normal in the tropical South Atlantic(Figure 24) and when dipole SST anomaly patterns withpositive north and negative south values are seen in thetropical Atlantic (Figure 25).
Accordingly, it can be inferred that the SST anomalies observed in the tropical Atlantic and the La Niña-like conditions seen contributed to anomalous atmospheric circulation over the North Atlantic, thereby
inducing eastward-stretching wave trains.

5 m/s

W/m2

Figure 22 Three-month mean 200-hPa velocity potential anomalies, 200-hPa divergent wind anomalies and outgoing longwave
radiation (OLR) anomalies for December 2011 – February 2012
The contours indicate velocity potential anomalies at intervals of 0.5 ×
106 m2/s. The vectors denote divergent wind anomalies (unit: m/s). The
shading indicates OLR anomalies (unit: W/m2). The cold- (warm-)color shading denotes enhanced (suppressed) convective activity.

x 10-6 /s/day

Figure 23 Rossby wave source anomalies at 200 hPa for
December 2011 – February 2012
The contours and shading indicate Rossby wave source anomalies (unit: 5 × 10-6 /s/day). Positive (warm-color) and negative (cold-color) anomalies represent vorticity sources andsinks, respectively.

3.3 Low temperatures across the Eurasian
mid-latitudes
In past La Niña periods, a tendency has been observedin the Eurasian mid-latitudes whereby temperatures in the
troposphere and geopotential heights in the upper troposphere are lower than normal (without a 90% confidence
level) (Figure 26). The related anomalies for winter2011/2012 (Figures 12 and 19) echo this tendency.
Steady response to diabatic heating anomalies around the
Maritime Continent was examined using a linear
baroclinic model (LBM; Watanabe and Kimoto 2000).
The LBM results (Figure 27) indicated that both lower-level temperatures and upper-level height were below
normal in the mid-latitudes of Eurasia, which was consistent with characteristics seen in past La Niña events.
(a) Z250

Figure 24 Three-month mean outgoing longwave radiation regressed onto area-averaged sea surface temperatures (unit: ˚C) in thetropical South Atlantic (green rectangle: 20˚S – eq., 40˚W – 10˚E) for
winters (December – February) from 1979/1980 to 2010/2011
The contour intervals are 1 W/m2, and positive and negative values arecolored in blue and red, respectively. The gray shading indicates a 95%
confidence level as indicated by t-testing.

Figure 25 Composite of three-month mean outgoing longwave radiation anomalies for winter (December – February) when tropical sea
surface temperatures were positive in the northwestern North Atlantic (dashed green rectangle: 5˚N – 20˚N, 75˚W – 40˚W) and negativein the South Atlantic (solid green rectangle: 20˚S – eq., 40˚W – 10˚E)
The winters selected for the composite are 1979/1980, 1980/1981,
1995/1996, 1996/1997, 2001/2002 and 2005/2006. The contour intervals
are 2 W/m2. The gray shading indicates a 95% confidence level as indicated by t-testing.
(c) 50˚E – 120˚E averaged Z and T(b) T850

˚C

Figure 26 La Niña composites of three-month mean (a) 250-hPa height anomalies, (b) 850-hPa temperature anomalies, and (c) zonally-averaged geopotential height and temperature anomalies (50˚E – 120˚E) for winter (December – February)(a) The contours indicate height anomalies at intervals of 10 m (shown between -50 m and 50 m). (b) The contours denote temperature anomalies
at intervals of 0.2˚C (shown between -1˚C and 1˚C). (c) The contours denote geopotential height anomalies at intervals of 5 m, and the shading
indicates temperature anomalies (unit: ˚C). (a) – (c) The past La Niña winters selected for the composites are those of 1984/1985, 1988/1989,
1995/1996, 1998/1999, 1999/2000, 2005/2006 and 2007/2008. The gray shading indicates a 90% confidence level as indicated by t-testing.

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No. 28 | Spring 2012

(a)

(b)

(c)

m
Figure 27 Steady response in a linear baroclinic model (LBM) to heating anomalies near the Maritime Continent(a) The red ellipse indicates diabatic heating for the LBM with the basic state for January (i.e., the 1979 – 2004 average based on
JRA-25 data). (b) The shading denotes the steady response of 250-hPa height anomalies (unit: m), and the vectors indicate wave activity fluxes (unit: m2/s2). (c) The shading indicates the steady response of 850-hPa temperature anomalies (unit: ˚C). (b) and (c) These
anomalies as responses represent deviations from the respective basic states and are additionally subtracted from the zonal averages of
the respective anomalies. The related steady responses to heating in the basic state for December and February (not shown) are similar
to those for January.

Accordingly, the La Niña-like conditions observed may
be responsible for low temperatures in the Eurasian middle latitudes.

tion of the Siberian High, leading to cold anomalies in
East Asia. Thus, the light sea ice observed around the
Barents Sea and the Kara Sea may contribute to the enhancement of the Siberian High.

3.4 Arctic sea ice
During winter 2011/2012, the sea ice extent in the Arctic Ocean, especially in the Barents Sea and the Kara Sea,
remained far below the 1979 – 2000 average (Figure 28).
According to statistical analysis (Figure 29), atmosphericcirculation anomalies over Eurasia seen in light sea ice
around the seas echoed related anomalies observed during
the winter (Figure 12). Recent studies (e.g., Honda et al.
2009, Inoue et al. 2012) have reported that a reduction in
the amount of floating sea ice tends to induce amplifica-(a) December 2011(b) January 2012

4. Summary
In the 2011/2012 Asian winter monsoon season, Central and East Asia experienced cold winter conditions due
to a strong Siberian High and frequent cold surges. The
possible primary factors contributing to these conditions
are summarized in Figure 30, but the related mechanisms
have not yet been fully clarified.
(1: Kazuyoshi Yoshimatsu, 2-4: Shotaro Tanaka,
Climate Prediction Division)(c) February 2012(d)Figure 28 Arctic sea ice extent for winter 2011/2012(a) – (c) Monthly Arctic sea ice extent for (a) December 2011, (b) January 2012 and (c) February 2012. The magenta line shows
the 1979 to 2000 median extent for that month. The black cross marks the geographic North Pole. (d) Daily Arctic sea ice extent
as of April 2, 2012, along with the corresponding values for the previous four years. The current year is shown in light blue, 2010
– 2011 in pink, 2009 – 2010 in dark blue, 2008 – 2009 in purple, and 2006 – 2007 (the year in which the record minimum wasseen) in dashed green. The gray area around the average line shows the two-standard-deviation range of the data.
(Sources: National Snow and Ice Data Center (NSIDC), USA, at http://nsidc.org/arcticseaicenews/)

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(a) Z500(b) SLP(c) T850

Figure 29 Three-month mean (a) 500-hPa height, (b) sea level pressure and (c) 850-hPa temperature regressed
onto area-averaged sea ice extents around the Barents Sea and the Kara Sea (70˚N – 80˚N, 45˚E – 90˚E) for winters(December – February) from 1979/1980 to 2010/2011
The contour intervals are (a) 5 m, (b) 0.4 hPa, and (c) 0.2˚C. Warm- (cold-) color contours indicate negative (positive) values. The gray shading indicates a 90% confidence level as indicated by t-testing. COBE-SST sea ice concentration data
were used for this analysis.

Figure 30

Primary factors contributing to cold winter conditions of 2011/2012 in Central and East Asia

References
Gill, A. E., 1980: Some simple solutions for heat-induced tropical circulation. Quart. J. Roy. Meteor. Soc., 106, 447 – 462.
Honda, M., J. Inoue, and S. Yamane, 2009: Influence of low
Arctic sea-ice minima on anomalously cold Eurasian winters.
Geophys.
Res.
Lett.,
36,
L08707,doi:
10.1029/2008GL037079.
Inoue, J., M. Hori, and K. Takaya, 2012: The Role of Barents Sea
Ice in the Wintertime Cyclone Track and Emergence of a
Warm-Arctic Cold-Siberian Anomaly. J. Climate, 25, 2561 –2568.
JMA, 2006: Characteristics of Global Sea Surface Temperature
Data (COBE-SST), Monthly Report on Climate System, Separated Volume No. 12.
Onogi, K., J. Tsutsui, H. Koide, M. Sakamoto, S. Kobayashi, H.
Hatsushika, T. Matsumoto, N. Yamazaki, H. Kamahori, K.
Takahashi, S. Kadokura, K. Wada, K. Kato, R. Oyama, T.
Ose, N. Mannoji and R. Taira, 2007: The JRA-25 Reanalysis.
J. Meteorol. Soc. Japan, 85, 369 – 432.

TCC News

Sardeshmukh, P. D., and B. J. Hoskins, 1988: The generation of
global rotational flow by steady idealized tropical divergence. J. Atmos. Sci., 45, 1228 – 1251.
Takaya, K., and H. Nakamura, 2001: A formulation of aphase-independent wave-activity flux for stationary and migratory quasigeostrophic eddies on a zonally varying basic
flow. J. Atom. Sci., 58, 608 – 627.
―, and ―, 2005a: Mechanisms of intraseasonal amplification of
the cold Siberian high. J. Atmos. Sci., 62, 4423 – 4440.
―, and ―, 2005b: Geographical dependence of upper-level
blocking formation associated with intraseasonal amplification of the Siberian high. J. Atmos. Sci., 62, 4441 – 4449.
Watanabe, M., and M. Kimoto, 2000: Atmospheric-ocean thermal coupling in North Atlantic: Apositive feedback, Quart.
J. R. Met. Soc., 126, 3343 – 3369.

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JMA’s Advisory Panel on Extreme Climate Events
To support the provision of timely statements on primaryfactors relating to ongoing extreme climate events, the Japan Meteorological Agency (JMA) established the Advisory
Panel on Extreme Climate Events in June 2007.

JMA routinely shares information on the current conditions of the climate system and discusses climatic anomalies with the Panel using a dedicated website and e-mailcommunication. The Agency developed the Interactive
Tools for Analysis of the Climate System (ITACS) for the
Panel to support analysis of the causes of extreme climate
events. ITACS is also provided to National Meteorologicaland Hydrological Services (NMHSs) to assist with theirrelated activities.
The Panel also advises JMA in regard to the improvement of climate diagnosis tools. New approaches introduced by the Agency based on Panel advisories include a
linearized baroclinic model (LBM) for the investigation of
stationary response to convective heating anomalies and amethod for diagnosing meridional-mean circulation using
mass-weighted isentropic zonal mean (MIM) meridional
velocity values.
Figure 31 shows the framework of the Panel, which is
positioned between JMA and the climate research community. It can be seen that the framework supports favorable
collaboration and cooperation between the academic andoperational services sectors. Panel-related activities, including discussions on diagnostic analysis and sharing of
the latest climatological findings, have helped JMA to enhance its ability for monitoring and analysis and to improve its climate services.

The Advisory Panel on Extreme Climate Events is
tasked with investigating extreme climate events based ona climatological approach so that it can advise JMA in
issuing statements on such events and recommend related
application of the latest findings. The Panel consists ofprominent climate scientists from Japanese universities andresearch institutes, and is chaired by Prof. Kimoto from the
University of Tokyo.
Essentially, when a nationwide-scale extreme climate
event that significantly impacts socio-economic activity
occurs, the Panel initiates investigation and discussion ofrelated factors with JMA experts. Following preliminary
discussions, it holds a meeting at JMA’s headquarters or
online, after which JMA issues a statement on matters suchas the outlook for the event based on the Panel’s investigation and advice. The statement is provided to the generalpublic and to decision makers in socio-economic sectors to
help them avoid or minimize adverse effects from theevent. Since the Panel was established in 2007, JMA has
issued a number of statements, including those related toheat waves in summer 2008, the record-breaking hotsummer of 2010 and the cold winter of 2011/2012.

(Shotaro Tanaka, Climate Prediction Division)

Figure 31 Framework between JMA and climate research community related to the Advisory
Panel on Extreme Climate Events

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Participation of TCC Experts in RCOFs and Expert Visits to NMHSs in
Southeast Asia
WMO Regional Climate Outlook Forums (RCOFs)
bring together national, regional and international climate
experts on an operational basis to produce regional climate outlooks based on input from participating NMHSs,
regional institutions, Regional Climate Centres and global
producers of climate predictions. By providing a platform
for countries with similar climatological characteristics todiscuss related matters, these forums ensure consistency
in terms of access to and interpretation of climate information.

from 19 to 20 April. At both the events, the TCC attendees gave presentations on seasonal predictions basedon JMA’s numerical model and participated in discussions
to produce consensus forecasts.
TCC experts also visited NMHSs in the Philippines,
Viet Nam and Lao PDR in March 2012 to provide follow-up for the TCC Training Seminar on one-monthforecast held in November 2011, including practical exercises with the Interactive Tool for Analysis of the Climate
System (ITACS) and the installation of a module forsite-specific probabilistic guidance for one-month forecasting. The experts also discussed and exchanged views
with attendees on improving climate services and engaging in possible future cooperation.

In 2012, TCC experts participated in two RCOFs. These were the eighth session of the Forum on Regional Climate Monitoring, Assessment and Prediction for Regional
Association II (FOCRAII) held in Beijing, China, from 6
to 8 April, and the third session of the South Asian Climate Outlook Forum (SASCOF-3) held in Pune, India,(Ryuji Yamada, Tokyo Climate Center)

Discussion at Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), Philippines

Presentation at FOCRA II, Beijing, China

Exercise at National Center for Hydro-Meteorological
Forecasting (NCHMF), Viet Nam

Lecture at Department of Meteorology and Hydrology(DMH), Lao PDR

Any comments or inquiry on this newsletter and/or the TCC
website would be much appreciated. Please e-mail to
tcc@met.kishou.go.jp.
(Editors: Teruko Manabe, Ryuji Yamada and Kenji Yoshida)

Tokyo Climate Center (TCC), Climate Prediction Division, JMA
Address: 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan
TCC Website: http://ds.data.jma.go.jp/tcc/tcc/index.html

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