No. 30

Autumn 2012
ContentsPage

El Niño Outlook (October 2012 – April 2013)

1

JM A’s Seasonal Numerical Ensemble Prediction for Winter 2012/2013

2

Cold Season Outlook for Winter 2012/2013 in Japan

4

Summary of the 2012 Asian Summer Monsoon

5

Extremely Hot Late-Summer Conditions in Northern and Eastern Japan in 20128

Sea Ice in the Arctic Ocean for the 2012 Summer Season

13

Status of the Antarctic Ozone Hole in 201214

El Niño Outlook (October 2012 – April 2013)
El Niño conditions, which had emerged in the Northern
Hemisphere summer, weakened in the equatorial Pacific.
The likelihood that El Niño conditions will last until the
Northern Hemisphere winter or transition to ENSO neutral
conditions during autumn and winter is equal.

depths of around 140 m (Figures 2 and 3b). In the atmosphere, convective activity was above normal over thewestern equatorial Pacific. Easterly winds in the lower
troposphere were weaker than normal in the western partand stronger than normal in the central part.
According to JMA's El Niño prediction model, SSTs in
the NINO.3 region will be mostly near normal during theprediction period (Figure 4). Taking prediction uncertainties into account, however, it remains possible that El Niño
conditions will persist until the Northern Hemisphere winter. Considering all the above, the likelihood that El Niño
conditions will last until the Northern Hemisphere winteror transition to ENSO neutral conditions during autumn
and winter is considered to be equal.

El Niño/La Niña
In September 2012, the SST deviation in the NINO.3
region was +0.3°C. SSTs in most parts from the central
equatorial Pacific to the eastern Pacific were above normal, but were closer to normal than in August (Figures 1
and 3a). Subsurface temperatures were above normal in
the western equatorial Pacific. Those in the central part,which had been above normal in August, moved closer tonormal, and below-normal temperatures were seen at

(a)

(a)

(b)

(b)

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

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

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No. 30 | Autumn 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 300 m. The base period for the normal is 1981 – 2010.

Western Pacific and Indian Ocean
The area-averaged SST in the tropical western Pacific (NINO.WEST) region was below normal in
September, and is likely to be near normal or below
normal in the months ahead.
The area-averaged SST in the tropical Indian
Ocean (IOBW) region was near normal in September,and is likely to be near normal in the months ahead.
(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 inorder to remove the effects of long-term trends.

Figure 4
Outlook of NINO.3 SST deviation produced by
the El Niño prediction modelThis figure shows a time series of 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 aprobability of 70%.

JMA’s Seasonal Numerical Ensemble Prediction for Winter 2012/2013
According to JMA’s seasonal ensemble prediction
system, convection is expected to be active over thetropical Indian Ocean and the central equatorial Pacificand inactive around the Maritime Continent and east of
the Philippines. In association with active convection
over the tropical Indian Ocean, the sub-tropical jet stream
is expected to shift northward over the western part of
the Eurasian Continent and air temperatures are expected
to be above normal around South Asia. Conversely, negative anomalies of air temperature are expected over the
mid-latitudes of the Eurasian Continent.

TCC News

1.

Introduction
This article outlines JMA’s dynamical seasonal ensemble prediction for winter 2012/2013 (December 2012 –February 2013, referred to as DJF), which was used as abasis for the Agency’s operational cold-season outlook
issued on 25 October, 2012. The outlook shown here isbased on the seasonal ensemble prediction system of the
Coupled atmosphere-ocean General Circulation Model(CGCM). See the column below for details of the system.
Section 2 outlines global SST anomaly predictions, andSection 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
discussed in Section 4.

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No. 30 | Autumn 2012

2. SST anomalies (Figure 5)
Figure 5 shows predicted SSTs and their anomalies for
DJF. Above-normal values are expected in the central partof the equatorial Pacific and the tropical Indian Ocean.

SST

3. Prediction for the tropics and sub-tropics (Figure 6)
Figure 6 (a) shows predicted precipitation and related
anomalies for DJF. In association with the SST anomaly
pattern over the equatorial Pacific, precipitation is expected to be above normal over the central equatorial Pacific and below normal around the Maritime Continentand east of the Philippines. From the tropical Indian
Ocean to Southeast Asia, above-normal precipitation is
expected. However, the results of hindcast experimentation indicate that the level of prediction skill for precipitation around Southeast Asia is relatively low. Accordingly,
the prediction of above-normal levels over Southeast Asiaand the related response to the large-scale atmosphericcirculation detailed later should be interpreted with caution.
Velocity potential in the upper troposphere (200 hPa)
(Figure 6 (b)) is expected to be negative (i.e., more divergent) over the tropical Indian Ocean and the central equatorial Pacific, reflecting active convection in these regions. Around the maritime continent, relatively positive(i.e., more convergent) anomalies are predicted, reflecting
inactive convection.
The stream function at 200 hPa (Figure 6 (c)) is generally expected to be negative (i.e., cyclonic) in the
mid-latitudes of the Northern Hemisphere, reflecting thezonal pattern of precipitation (i.e., active near the equatorand inactive in the subtropics of the Northern Hemisphere). From South to Southeast Asia, positive (i.e., an-Figure 5 Predicted SSTs (contours) and SST anomalies(shading) for December 2012 – February 2013 (ensemble
mean of 51 members)

ti-cyclonic) anomalies are expected, reflecting active
convection from the tropical Indian Ocean to Southeast
Asia. In association with this, the sub-tropical jet stream is
expected to shift northward over the western part of theEurasian Continent and above-normal air temperatures are
expected around South Asia (not shown). However, theprediction of these anomalies around Southeast Asia
should be interpreted with caution because they may beaffected by active convection over Southeast Asia, which
is predicted with insufficient reliability.
Stream function anomalies at 850 hPa (Figure 6 (d)) are
expected to be negative over the northern Indian Ocean inassociation with active convection in the region. Positive
anomalies are predicted over the western tropical Pacificin association with inactive convection around the Maritime Continent and east of the Philippines.

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

Figure 6 Predicted atmospheric fields from 60°N – 60°S for December 2012 – February 2013 (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 × 10 6 m2/s.
(d) Stream function at 850 hPa (contours) and anomaly (shading). The contour interval is 5 × 106 m2/s.

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No. 30 | Autumn 2012

be attributable to active convection covering the area fromthe tropical Indian Ocean to Southeast Asia. Accordingly,
lower-atmospheric temperatures are expected to be below
normal over the mid-latitudes of the Eurasian Continent(Figure 7(c)). However, the prediction of negative anomalies around East Asia should be interpreted with caution
because they may be affected by active convection overSoutheast Asia, which is predicted with insufficient reliability.

4. Prediction for the mid- and high latitudes of theNorthern Hemisphere (Figure 7)
Around the Aleutian Low region, sea level pressure(SLP) anomalies (Figure 7(a)) are expected to be positiveon the northern side and negative on the southern side,suggesting that the Aleutian Low will shift southward but
its strength will be near normal. Conditions of the northwesterly winter monsoon are therefore expected to be nearnormal over East Asia. Negative anomalies of 500-hPa
geopotential height (Figure 7(b)) are widely expected overthe southern part of the Eurasian Continent, and this may(a)SLP(Masayuki Hirai, Climate Prediction Division)(c)T850(b)Z500-4-16 -12

-8

-4

0

4

8

12

16

-120 -90 -60 -30

0

30

60

-3

-2

-1

0

1

2

3

4

90 120Figure 7 Predicted atmospheric fields from 20°N – 90°N for December 2012 – February 2013 (ensemble mean of 51 members)(a) Sea level pressure (contours) and anomaly (shaded). The contour interval is 4 hPa.
(b) 500-hPa height (contours) and anomaly (shaded). The contour interval is 60 m.
(c) 850-hPa temperature (contours) and anomaly (shaded). The contour interval is 3˚C.
JMA’s Seasonal Ensemble Prediction System
JMA operates a seasonal Ensemble Prediction System (EPS) using the Coupled atmosphere-ocean General Circulation Model(CGCM) 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 consists of 51 members from the latest 6 initial dates (9 members are run every 5 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/.

Cold Season Outlook for Winter 2012/2013 in JapanFor winter 2012/2013, mean temperatures are likely to be
above or near normal in eastern Japan, western Japan andOkinawa/Amami. Cold-season precipitation amounts arelikely to be above or near normal in Okinawa/Amami.

2012/2013, mean temperatures are likely to be above ornear normal in eastern Japan, western Japan and Okinawa/Amami with 40% probability for both categories (Figure 8). Cold season precipitation amounts are likely to be
above or near normal in Okinawa/Amami with 40%
probability for both categories (Figure 9).

1. Outlook summary
JMA issued its outlook for the coming winter over Japan in September and updated it in October. For winterCategory–0+

Northern Japan

30

40

30

Eastern Japan

20

40

40

Western Japan

20

40

40

Okinawa and Amami

20

40

40

NorthernJapan

WesternJapan

Figure 8 Outlook for winter 2012/2013 temperatureprobability in JapanTCC News

EasternJapan

Okinawa/Amami

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No. 30 | Autumn 2012

2. Outlook background
JMA's coupled global circulation model predicts that
the NINO.3 SST will be mostly near normal during theNorthern Hemisphere autumn and winter. Taking prediction uncertainties into account, however, it remains possible that El Niño conditions will persist until winter.
Considering all the above, the likelihood that El Niño
conditions will last until winter or transition to ENSO
neutral conditions during autumn and winter is equal.
In association with the SST anomaly pattern, somecharacteristics of the ensemble averaged atmospheric circulation anomaly pattern predicted by the model are similar to those of typical El Niño events in and around thetropics. For example, convection is expected to be inactivein the western tropical Pacific. In line with this, an anti-cyclonic circulation anomaly in the lower troposphere ispredicted. There is a possibility that an anti-cyclonic circulation anomaly extending to the south of Japan willbring warm and humid air to the southern part of thecountry and create favorable conditions for cyclone gene-sis there.
Remarkable southward meandering of the jet stream
over Japan is predicted in association with active convection around the Bay of Bengal. However, the model
hindcast (30 years from 1979 to 2008) suggests that themodel’s skill is insufficient to predict convection aroundthe Bay of Bengal. Moreover, the positive (negative)
phase of the Arctic Oscillation (AO) tends to cause aweak (strong) winter monsoon and above-normal (below-normal) temperatures in northern Japan. However,
the model results associated with the AO should be treatedwith caution because the spread of the AO index among
ensemble members is large.
Considering the prediction skill of the model’s resultsin the mid- and high-latitudes described above, it is most
likely that El Niño characteristics will be observed around
Japan in response to tropical conditions.
(Takafumi Umeda, Climate Prediction Division)

–

0

+

Sea of Japan side

30

40

30

Pacific side

30

40

30

Sea of Japan side

40

30

30

Pacific side

30

30

40

Sea of Japan side

30

40

30

Pacific side

30

30

40

20

40

40

Category
Northern Japan
Sea of Japan side
Eastern Japan
Sea of Japan side

Northern Japan

Northern Japan
Pacific side

Eastern Japan

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

Western Japan
Okinawa and Amami

Okinawa/Amami

Figure 9 Outlook for winter 2012/2013 precipitation probability in Japan

Summary of the 2012 Asian Summer Monsoon
1. Precipitation and temperature
Four-month total precipitation amounts based on
CLIMAT reports during the monsoon season (June – September) were above 200% of the normal around southern
Pakistan, and were below 60% of the normal around Java
Island (Figure 10). Values were mostly consistent with the
distribution of OLR anomalies (Figure 12).
Extremely heavy precipitation was seen around Mongo-

lia in June and July and over Pakistan in September. In
contrast, extremely light precipitation was seen in western
India in June and around western Indonesia in August(figures not shown).
Four-month mean temperatures for the same period
were 1°C above the normal in northern Japan and fromwestern Mongolia to northeastern India, and were 1°C
below the normal from northeastern China to eastern

Figure 10 Four-month precipitation ratios (%) from
June to September 2012
The base period for the normal is 1981 – 2010.

Figure 11 Four-month mean temperature anomalies(°C) from June to September 2012
The base period for the normal is 1981 – 2010.

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No. 30 | Autumn 2012

Mongolia and in northern Pakistan (Figure 11).
It was reported that heavy rains caused more than 130 fatalities in Bangladesh and more than 120 fatalities in northern India’s Assam region in June. It was also reported thatheavy rains caused at least 100 fatalities in the Philippines
due to typhoons and enhanced convective activity associatedwith monsoon in August. It was further reported that heavy
rains from late August to September caused more than 450
fatalities in Pakistan.
2. Tropical cyclones
During the monsoon season, 16 tropical cyclones (TCs) oftropical storm (TS) intensity or higher formed over the western North Pacific (Table 1). The number of formations was
the same as the 1981 – 2010 average of 16.0. A total of 8
among these 16 passed around the East China Sea and approached or hit China, the Korean Peninsula or Japan, while
five approached or hit southern China or Viet Nam via theSouth China Sea. Two TCs hit the main islands of Japan.
Typhoon Saola caused more than 70 fatalities throughout
China and the Philippines, and Typhoon Kai-tak caused morethan 35 fatalities throughout the Philippines and Viet Nam.
Note: Disaster information is based on reports by governmental organizations (Bangladesh, China, India, Pakistan,
the Philippines and Viet Nam).
3. Monsoon activity and atmospheric circulation
Convective activity (inferred from outgoing longwave radiation (OLR)) averaged for June – September 2012 wasenhanced over the western Indian Ocean, Pakistan, northern
India, the Bay of Bengal, the South China Sea and the tropical western Pacific, and was suppressed over western/southern India and the eastern Indian Ocean (Figure 12).
According to the OLR indices (Table 2), convective activity
averaged over the Bay of Bengal and in the vicinity of thePhilippines (both core areas of monsoon-related active convection) was enhanced in the summer monsoon season except in August, and in particular, enhanced convective activity from the South China Sea to the area east of the Philippines persisted throughout the season (Figure 13). The
large-scale active convection area of the monsoon showed atendency to be shifted north and east of its normal position.
The areas of active convection that were originally enhanced
around the equatorial western Indian Ocean in the middle ofAugust moved northward around India and reached Pakistan
in early September (Figure 14 (a)).

Table 1 Tropical cyclones forming over the western
North Pacific from June to September 2012
Number
ID

Name

Date
(UTC)

Category1)

T1203
T1204
T1205
T1206
T1207
T1208
T1209
T1210
T1211
T1212
T1213
T1214
T1215
T1216
T1217
T1218

MAWAR
GUCHOLTALIMDOKSURIKHANUNVICENTESAOLADAMREYHAIKUIKIROGI
KAI-TAKTEMBINBOLAVENSANBA
JELAWATEWINIAR

6/1 – 6/6
6/13 – 6/19
6/17 – 6/20
6/26 – 6/29
7/16 – 7/18
7/21 – 7/24
7/28 – 8/3
7/28 – 8/3
8/3 – 8/9
8/6 – 8/10
8/13 – 8/18
8/19 – 8/30
8/20 – 8/29
9/11 – 9/17
9/20 – 10/1
9/24 – 9/29

TY
TY
STS
TS
STS
TY
TY
TY
TY
STS
TY
TY
TY
TY
TY
STS

Maximum
wind2)(knots)
75
100
50
40
50
80
70
70
65
50
65
80
100
110
110
50

Note: Based on information from the RSMC Tokyo-Typhoon
Center.
1) Intensity classification for tropical cyclones
TS: Tropical storm, STS: Severe tropical storm, TY: Typhoon2) Estimated maximum 10-minute mean wind

Figure 12 Four-month mean outgoing longwave radiation(OLR) and its anomaly for June – September 2012
The contours indicate OLR at intervals of 10 W/m2, and thecolor shading denotes OLR anomalies from the normal (i.e., the1981 – 2010 average). Negative (cold color) and positive (warmcolor) OLR anomalies show enhanced and suppressed convection compared to the normal, respectively. Original data provided by NOAA.

Table 2 Summer Asian Monsoon OLR Index (SAMOI) from May to October 2012
Asian summer monsoon OLR indices (SAMOI) are derived from OLR anomalies from May to October. SAMOI (A), (N) and(W) indicate the overall activity of the Asian summer monsoon, its northward shift and its westward shift, respectively. SAMOI
definitions are as follows: SAMOI (A) = (–1) × (W + E); SAMOI (N) = S – N; SAMOI (W) = E – W. W, E, N and S indicate
area-averaged OLR anomalies for the respective regions shown in the figure on the right normalized by their standard deviations.
Summer As i a n Mons oon OLR Index (SAMOI)Ma y 2012
Jun. 2012
Jul . 2012
Aug. 2012
Sep. 2012
Oct. 2012

TCC News

SAMOI (A):SAMOI (N):SAMOI (W):

Activity

Northward-shift

Westward-shift

-0.9
1.2
0.3
1.5
0.2
-1.2

-0.8
-1.5
-1.4
-1.0
0.2
-1.2

0.7
0.7
1.0
-0.1
1.6
-0.7

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No. 30 | Autumn 2012

Figure 13 Time-series representation of the area-averaged OLR index (OLR-PH) around the Philippines(shown by the blue rectangle on the right: 10ºN – 20ºN, 110ºE – 140ºE)
The OLR index (OLR-PH) consists of reversed-sign area-averaged OLR anomalies for the area around the Philippines normalized by the standard deviation. Positive and negative OLR index values indicate enhanced and suppressed convective activity, respectively, compared to the normal (i.e., the 1981 – 2010 average). The thick and thinblue lines indicate seven-day running mean and daily mean values, respectively.

In the upper troposphere, the Tibetan High was pronounced around its central part (Figure 15 (a)). In thelower troposphere, a prominent monsoon trough stretching from the South China Sea to the Philippines was observed, and westerly winds were stronger than normal
from the Bay of Bengal to the vicinity of the Philippines(Figure 15 (b)). Easterly vertical shear over the North Indian Ocean and southern Asia was stronger than normal(Figure 16). These characteristics of anomalous circulation indicate enhanced large-scale circulation related tothe monsoon. The Pacific High in the lower troposphere
was significantly enhanced to the east of Japan, bringing
hot summer conditions to the country (Figure 15 (b)).

(a)

(b)

(1-2: Kazuyoshi Yoshimatsu, 3: Shotaro Tanaka,
Climate Prediction Division)

Figure 14 Latitude-time cross section of the five-day runningmean OLR from May to October 2012 ((a) India (65ºE – 85ºEmean), (b) area east of the Philippines (125ºE – 145ºE mean))
The thick black lines indicate the climatological mean OLR(W/m2) for the period from 1981 to 2010, and the shading denotes
the OLR for 2012.

References
Webster, P. J., and S. Yang, 1992: Monsoon and ENSO:
Selectively interactive systems. Quart. J. Roy. Meteor.
Soc., 118, 877-926.

Figure 15 Four-month mean stream function and its anomaly for June – September 2012(a) The contours indicate the 200-hPa stream function at intervals of 10 × 106 m2/s, and the color shading indicates 200-hPa stream
function anomalies from the normal. (b) The contours indicate the 850-hPa stream function at intervals of 4 × 106 m2/s, and the color
shading indicates 850-hPa stream function anomalies from the normal. The base period for the normal is 1981 – 2010. Warm (cold)
shading denotes anticyclonic (cyclonic) circulation anomalies in the Northern Hemisphere, and vice versa in the Southern Hemisphere.

Figure 16 Time-series representation of the zonal wind shear index between 200 hPa and 850 hPa averaged over the North
Indian Ocean and southern Asia (pink rectangle on the right: equator – 20ºN, 40ºE – 110ºE)
The zonal wind shear index is calculated after Webster and Yang (1992). The thick and thin pink lines indicate seven-day runningmean and daily mean values, respectively. The black line denotes the normal (i.e., the 1981 – 2010 average), and the gray shadingshows the range of the standard deviation calculated for the time period of the normal.

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No. 30 | Autumn 2012

Extremely Hot Late-Summer Conditions in Northern and EasternJapan in 2012
Northern and eastern Japan experienced extremely hightemperatures in the late summer of 2012 due to the significantly enhanced North Pacific High to the east of the country. Record-high temperatures were set over northern Japanfor three consecutive 10-day periods* from late August to
mid-September. The 10-day mean sea surface temperature(SST) averaged over the area around northern Japan for
mid-September was the highest on record for all 10-day
periods of the year since 1985.

2012

Jul.

Aug.

Sep.

NorthernJapan

EasternJapan

WesternJapan* Note: There are three 10-day periods in each month,making a total of thirty-six in a year. The third nominal
10-day period of each month may not in fact have only 10days (e.g., the third 10-day period of August covers 11
days from the 21st to 31st).

OkinawaandAmami

1. Surface climate conditions
In northern and eastern Japan, hot sunny conditions
prevailed from mid-August to mid-September, and temperatures remained significantly above normal for thistime of the year (Figure 17). For example, Sapporo City
in northern Japan’s Hokkaido region experienced very hot
conditions every day from late August to mid-September,and daily mean temperatures persisted above the annual
high of the climatological normal (Figure 18).
The values of 10-day mean temperatures averaged overnorthern Japan were the highest on record for three consecutive 10-day periods from late August to
mid-September (Table 3, top). Those for eastern Japan
were the second highest on record for late August andearly September, and the value for mid-September tiedthe record-high set in 2011 (Table 3, bottom). Collectionof 10-day mean temperature records for divisions of Japan began in 1961.

Figure 17 Time-series representation of five-day runningmean temperature anomalies (unit: ˚C) for four divisions ofJapan from 1 July to 30 September, 2012
Anomalies are deviations from the 1981 – 2010 average.
Table 3 Top three 10-day mean temperature anomalies(unit: ˚C) averaged over northern Japan (top) and easternJapan (bottom) from late August to mid-September
Collection of statistical records began in 1961. Anomalies are
deviations from the 1981 – 2010 average, and the figures in red
denote records for 2012.
Northern Japan
21 – 31 August
1 – 10 September
11 – 20 September

Highest+3.5 (2012)+3.3 (2012)+5.5 (2012)

2nd highest+3.1 (2010)+3.1 (2010)+2.0 (2000)

3rd highest+1.9 (2000)+2.5 (2011)+1.8 (2007)

Eastern Japan
21 – 31 August
1 – 10 September
11 – 20 September

Highest+2.7 (2010)+2.9 (2010)+3.1 (2012)

2nd highest+2.1 (2012)+1.5 (2012)+3.1 (2011)

3rd highest+1.7 (2000)+1.5 (1961)+2.3 (2003)

Figure 18 Time-series representation of five-day running mean temperatures in Sapporo from 3 August to 18
September between 1961 and 2012
The red and blue lines indicate values for 2012 and 2010 (the previous record for high temperatures in late summer),
respectively. Green denotes the highest value among daily mean temperatures in the climatological normal (i.e., the1981 – 2010 average) for Sapporo.

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No. 30 | Autumn 2012

The Pacific High to the east of Japan in late August –mid-September was at its strongest for this time of theyear since 1979 (Figure 20 (b)). The westerly jet stream in
the upper troposphere showed significant northward meandering near Japan (Figure 21) in line with prominent
anticyclonic circulation anomalies centered over the area
to the northeast of the country (Figure 22). In association,negative anomalies of potential vorticity (PV) in the upper
troposphere were centered northeast of Japan (Figure 23).

2. Characteristic atmospheric circulation causing Japan’s hot late-summer conditions
The significantly enhanced Pacific High to the east ofJapan persisted from late August to mid-September 2012
(Figures 19 and 20 (a)). Northern and eastern Japan experienced extremely high temperatures due to southerly
warm-air advection and sunny conditions (i.e.,
above-normal amounts of solar radiation) attributed to thenorthward extension of this high.

Figure 19 Sea level pressure (SLP) averaged from 21 August to 20 September for (a) 2012, (b) the normal (i.e.,the 1981 – 2010 average) and (c) 2012 and anomalies (i.e., deviations from the normal)
The contour interval is 2 hPa.

Figure 20 (a) Time-series representation of five-day running mean values of SLP anomalies (unit: hPa) averaged
over the area east of Japan (30˚N – 45˚N, 140˚E – 170˚E) from 1 August to 30 September, 2012, and (b) interannual
variability of area-mean SLP anomalies averaged between 21 August and 20 September from 1979 to 2012
Anomalies are deviations from the 1981 – 2010 average. The red rectangle in the panel on the left shows the period from
21 August to 20 September, 2012.

Figure 22 200-hPa stream function (contours) andanomalies (shading) averaged from 21 August to 20
September, 2012
The contour interval is 106 m2/s. Positive (warm color)and negative (cold color) stream function anomalies in
the Northern Hemisphere indicate anticyclonic and cyclonic circulation anomalies. Anomalies are deviations
from the 1981 – 2010 average.

Figure 21 200-hPa wind vectors and zonal windspeeds averaged from 21 August to 20 September,
2012
The shading shows zonal wind speeds (unit: m/s).

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No. 30 | Autumn 2012

The enhanced anticyclone east of the country featured
an equivalent barotropic structure and a warm air
mass, and its vertical axis exhibited a slight northwardtilt with height (Figure 24). It is presumed that upper-level PV anomalies induced the enhanced equivalent-barotropic anticyclone (Hoskins et al. 1985).
In the upper troposphere, wave trains were seenalong the Asian jet stream in association with theeastward propagation of Rossby wave packets (Figure25). Convective activity associated with the Asiansummer monsoon was enhanced over the ArabianSea, Pakistan, India and the Bay of Bengal (Figure26). According to statistical analysis, when convective
activity is enhanced over these areas in and around
South Asia from late August to mid-September, wave
trains with anticyclonic circulation anomalies north ofJapan tend to appear along the Asian jet stream (Figure 27) as seen in 2012 (Figure 25). These trains are
similar to those of the Silk Road pattern highlighted
by T. Enomoto (Enomoto et al. 2003; Enomoto 2004).
It can be presumed from the results of statistical analysis and research performed to date that active convection associated with monsoon activity in andaround South Asia contributed to the development of
the enhanced anticyclone near Japan through theeastward propagation of quasi-stationary Rossby wave
packets along the Asian jet.

Figure 23 Potential vorticity on the 340 K isentropic
surface (contours; unit: s-1) and normalized anomalies(shading) averaged from 21 August to 20 September, 2012
Anomalies (i.e., deviations from the 1981 – 2010 average) arenormalized by their standard deviations.

Figure 24 The vertical-meridional section of stream
function anomalies (contours; unit: 106 m2/s) and temperature anomalies (shading; unit: ˚C) averaged from 21
August to 20 September, 2012, along the 150˚E meridian
Anomalies are deviations from the 1981 – 2010 average.

Figure 25 200-hPa stream function anomalies (contours),
200-hPa wave activity flux (vectors; unit: m2/s2), and outgoing longwave radiation (OLR) anomalies averaged from
21 August to 20 September, 2012
“A” and “C” indicate the centers of anticyclonic and cyclonic
circulation anomalies, respectively. The contour interval is 3 ×
106 m2/s. Negative (cold color) and positive (warm color) OLR
anomalies (unit: W/m2) show enhanced and suppressed convection, respectively. Anomalies are deviations from the 1981 –2010 average. The wave activity flux is calculated after Takaya
and Nakamura (2001).

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Figure 26 OLR anomalies averaged from 21 August to
20 September, 2012
The green and purple rectangles indicate the area around
South Asia (5˚N – 35˚N, 50˚E – 90˚E) and the area northeastof the Philippines (10˚N – 25˚N, 120˚E –150˚E), respectively. Anomalies are deviations from the 1981 – 2010 average.

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In late August and mid-September 2012, convective
activity was enhanced northeast of the Philippines (Figure 26); several typhoons formed in the area, moving
northward over Okinawa (southwestern Japan) and theSouth China Sea (Figure 28). According to statisticalanalysis, wave trains tend to appear in the area from thePhilippines to Japan and the northern Pacific in association with the variability of convective activity northeastof the Philippines from late August to mid-September(Figure 29). This teleconnection formation is called thePacific-Japan (PJ) pattern (Nitta 1986; 1987). The outcomes of statistical analysis and research performed todate indicate that active convection northeast of thePhilippines and typhoons contributed to the strength of
the Pacific High over northern and eastern Japan.
The possible primary factors contributing to Japan’s
hot late-summer conditions are summarized in Figure
30, but the related mechanisms have not yet been fully
clarified.

Figure 28

Typhoons forming from late August to mid-September 2012

Figure 29 500-hPa geopotential height (contours; unit: m) regressed onto a time-series
representation of area-averaged OLR values forthe area northeast of the Philippines (purple
rectangle: 10˚N – 25˚N, 120˚E – 150˚E) covering
the period from 21 August to 20 September
The contour interval is 3 m. The gray shading indicates a 95% confidence level. The base period
for the statistical analysis is 1979 – 2011.

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Figure 27 200-hPa geopotential height (contours; unit: m)regressed onto a time-series representation of area-averaged
OLR values in and around South Asia (green rectangle: 5˚N– 35˚N, 50˚E – 90˚E) for the period from 21 August to 20
September, 2012
The contour interval is 5 m. The gray shading indicates a 95%
confidence level. The base period for the statistical analysis is1979 – 2011.

Figure 30 Primary factors contributing to the hot late-summer conditionsof 2012 in northern and eastern Japan11

No. 30 | Autumn 2012

3. Sea surface temperatures around northern Japan
Sea surface temperatures (SSTs) around northern Japan were significantly
higher than normal (i.e., the 1981 – 2010 average) from late August to
mid-September 2012 (Figure 31). The value of 10-day mean SSTs averaged
for the area around Hokkaido (the white rectangle in Figure 31) for
mid-September 2012 was 22.5˚C (preliminary), which was 4.6˚C above
normal (Table 4) and exceeded the previous record of 21.4˚C set in late August 2010 for all 10-day periods of the year since 1985. In the normal, SSTs
in the area reach annual maximum levels in August and September. The
values of area-averaged SSTs for the two consecutive 10-day periods of early and mid-September 2012 were the highest on record for the respective
periods of the year since 1985 (Table 4; Figure 32).
In the seas around Hokkaido, surface seawater was warmer than normal
due to predominant sunny conditions (i.e., above-normal amounts of solar
radiation) associated with the enhanced North Pacific High that caused record-breaking high temperatures in northern Japan. In addition, near-surface
seawater was less mixed with cold seawater below it by surface winds, andocean heat accumulated between the surface and just above 10 m in depth
due to calm conditions associated with the enhanced Pacific High (Figure33). The record-high SSTs observed around Hokkaido can be attributed tothese factors relating to the enhanced North Pacific High east of Japan.
(1-2: Shotaro Tanaka, Climate Prediction Division,
3: Satoshi Matsumoto: Office of Marine Prediction)
References
Enomoto, T., B. J. Hoskins, and Y. Matsuda, 2003: The formation mechanism of theBonin high in August, Quart J. Roy. Meteor. Soc., 587, 157-178.
Enomoto, T., 2004: Interannual variability of the Bonin high associated with the
propagation of Rossby waves along the Asian jet. J. Meteor. Soc. Japan, 82,
1019-1034.
Hoskins, B., M. E. McIntyre, and A. W. Robertson, 1985: On the use and significance of isentropic potential vorticity maps, Quart J. Roy. Meteor. Soc., 111,
877-946.
Nitta, T., 1986: Long-term variations of cloud amount in the western Pacific region.
J. Meteor. Soc. Japan, 64, 373-390.
Nitta, T., 1987: Convective activities in the tropical western Pacific and their impact
on the Northern Hemisphere summer circulation. J. Meteor. Soc. Japan, 65,
373-390.
Takaya, K., and H. Nakamura, 2001: A formulation of a phase-independentwave-activity flux for stationary and migratory quasigeostrophic eddies on a zonally varying basic flow. J. Atom. Sci., 58, 608 – 627.

Figure 31 10-day mean SSTs (left) and anomalies (right) for late August (top), early September(middle) and mid-September 2012 (bottom)
Anomalies are deviations from the 1981 – 2010average, and the unit for SSTs and anomalies is ˚C.
The white rectangle indicates the target area around
Hokkaido.

Table 4 Record-high (preliminary) 10-day mean SSTs (unit: ˚C) averaged
over the area around Hokkaido in northern Japan for early and mid-September
The SST values for September 2012 are preliminary. Collection of statistical records
began in 1985, since when SST statistics have been based on satellite observations inaddition to ship observations. Anomalies are deviations from the 1981 – 2010 average. The area for the average is the white rectangle shown in Figure 31.
Seas around
Hokkaido
1 – 10 September
11 – 20 September

Area-averaged
SSTs
21.8
22.5

Anomalies
+3.3
+4.6

Previous record
high21.1 (2010)
20.1 (1999)

Figure 32 Interannual variability of 10-day mean SSTs averaged over the area around Hokkaido (white rectangle shownin Figure 31) for late August (green line), early September(blue line) and mid-September (red line) from 1985 to 2012

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Figure 33 Temperature profile for seawater
between the surface and a depth of 50 m averaged
over the area around Hokkaido (white rectangle
shown in Figure 31) for mid-September of 2012
(red line) and the 1985 – 2010 average (black line)
Deviations from the 1985 – 2010 average were significant between the surface and just above 10 m indepth, and were small at 50 m in depth.

No. 30 | Autumn 2012

Sea Ice in the Arctic Ocean for the 2012 Summer Season
The sea ice extent in the Arctic Ocean for the 2012 summer
season was the smallest since 1979.
On 5 March, 2012, the sea ice extent in the Arctic Ocean
reached its annual maximum of 15.48 million square kilometers (nearly normal based on the 1981 – 2010 average;
Figure 34) before decreasing at a nearly normal rate until theend of May. However, the rate of decrease in the Arctic
Ocean has been rapid since early June, meaning that the sea
ice extent there has been at or close to its minimum since
mid-June. The rate of decrease is usually slow in August,
but was rapid in August 2012.
On 19 August, the sea ice extent was below
4.31 million square kilometers, which was thesecond smallest recorded in 2007 since 1979,
and reached 3.42 million square kilometers on 13
September.

Figure 34 Time-series representation of daily sea ice extents in the Arctic Ocean from 1 January 2007 to 25 September 2012 and the normal (i.e., the 1981 – 2010 average)

Annual minimum sea ice extent in the Arctic
Ocean
When the sea ice extent in the Arctic Ocean
reached its minimum, extents around the Canadian Archipelago, the Beaufort Sea, the Laptev
Sea and the Kara Sea were considerably reduced.
This made the ice-free area north of the North
American continent and the Eurasian continent
larger than it was in September 2007 (Figure 35).
Summer weather conditions over the Arctic Ocean andfactors behind the remarkable decrease in the sea ice
extent
The pressure pattern from June to August of 2012 featured a high-pressure area centered over Greenland and alow-pressure area near Siberia. Contributing to the remarkable decrease of the sea ice extent were higher-than-normal
air temperatures over the Canadian Archipelago and theBeaufort Sea due to an inflow of warm southerly winds onthe eastern side of the low-pressure area near Siberia. An
early-August area of developed low pressure centered over
the Arctic Ocean that caused sea ice to melt rapidly is considered to be another factor behind the remarkable decrease.
The pressure patterns observed from June to August of 2007
(when the second-smallest sea ice extent on record was observed) and from June to July of 2011 (when thethird-smallest was observed), which featured ahigh-pressure area centered near the Beaufort Sea and alow-pressure area centered over Siberia, differed from thatseen from June to August of 2012. The factors contributing
to the decreases in the sea ice extent in 2007 and 2011 were:(1) warm winds flowing from the Bering Sea to the sea
along Siberia; (2) westward movement of sea ice north ofSiberia; and (3) sea ice flow out to the Atlantic Ocean via
the sea east of Greenland (Figure 36). A long-term downward trend for the sea ice extent in the Arctic Ocean is seen
(Figure 37). The factors causing the smallest sea ice extent
for summer 2012 are considered to be the long-term trend of
decrease and prevailing weather conditions.

Figure 35 Annual minimum sea ice extents in the Arctic Ocean
Annual minimum sea ice extents for 2007 (left), 2011 (center) and2012 (right)

Figure 36 Schematic representation of summer weather
patterns over the Arctic Ocean
Left: weather patterns for 2007 and 2011; right: weather patterns for 2012

Figure 37 Interannual variations of annual minimum
sea ice extent in the Arctic Ocean
The blue line indicates interannual variations of the annual
minimum sea ice extent from 1979 to 2012. The dashedline indicates the trend for 1979 to 2012.

(Keiji Hamada, Office of Marine Prediction)

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No. 30 | Autumn 2012

Status of the Antarctic Ozone Hole in 2012
The ozone hole was at its smallest since the 1990s.

meters (upper left panel), which is 1.5 times the area of
the Antarctic Continent. The gray shading in the bottom
panels indicates the progress of the hole’s development
and intensity this year.
The ozone layer acts as a shield against ultraviolet radiation, which can cause skin cancer. The ozone hole first
appeared in the early 1980s and reached its maximum sizeof 29.6 million square kilometers in 2000. Although thisyear’s was the smallest since the 1990s, the amount ofozone in the Antarctic region is expected to return topre-1980 levels in the late 21st century according to
WMO/UNEP Scientific Assessment of Ozone Depletion:
2010. Close observation of the ozone layer on a global
scale (including that over the Antarctic region) remains
important.

The Antarctic ozone hole in 2012 was the smallest interms of its annual maximum area since the 1990s (see theupper right panel in Figure 38) according to JMA’s analysis based on data from National Aeronautics and Space
Administration (NASA) satellites. Higher temperatures in
the lower stratosphere contributed to the smaller coverageof the hole during Antarctic spring. However, the hole isstill large compared to its size in the early 1980s, which isconsistent with the high levels of ozone-depleting substances in the Antarctic atmosphere.
Over the last 30 years, the Antarctic ozone hole has
appeared every year in Austral spring with a peak in September or early October. In 2012, it formed in mid-Augustand expanded rapidly from late August to early September, reaching its maximum size for the year on 22 September. At this time it covered 20.8 million square kilo-(Hiroaki Naoe, Ozone Layer Monitoring Office,Atmospheric Environment Division)

Figure 38
Antarctic ozone hole characteristics
Upper left: Time-series representation of the daily ozone-hole area for 2012 (red line) and the 2002–2011 average(black line). The blue shading area represents the range of daily minima and daily maxima over the past 10 years.
Upper right: Interannual variability in the annual maximum ozone-hole area. Bottom: Snapshots of total column ozone
distribution on selected days in 2012; the ozone hole is shown in gray. These panels are based on data from NASA satellite sensors of the total ozone mapping spectrometer (TOMS) and ozone monitoring instrument (OMI).

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)

TCC News

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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No. 30 | Autumn 2012