14 June 2013
Japan Meteorological Agency
Monthly Highlights on the Climate System (May 2013)
Highlights in May 2013
- Monthly precipitation amounts were significantly below normal and monthly sunshine durations were significantly above
normal in eastern and western Japan.
- Monthly mean temperatures were extremely low in western Europe and monthly precipitation amounts were extremely heavy
from eastern to western Europe.
- A ridge and trough were seen to the west and east of Japan, respectively. A blocking ridge developed around the Kamchatka
Peninsula.
- Convective activity was enhanced over the North Indian Ocean and south of Indonesia, and was suppressed around the
equatorial date line region.
- In the equatorial Pacific, remarkably negative SST anomalies were seen in the eastern part.
Climate in Japan:
Monthly precipitation amounts were significantly below
normal and monthly sunshine durations were significantly
above normal in eastern and western Japan (Fig. 1) due to
frequent passage of high pressure systems. Meanwhile,
monthly sunshine duration was significantly below normal
on the Sea of Japan side of northern Japan by the influence of
cold air and cyclones.
World Climate:
The monthly anomaly of the global average surface
temperature in May 2013 (i.e., the combined average of the
near-surface air temperature over land and the SST) was
+0.20 °C (4th warmest since 1891) (preliminary value) (Fig.
2). On a longer time scale, global average surface
temperatures have risen at a rate of about 0.68°C per century
in May (preliminary value).
Extreme climate events were as follows (Fig. 3).
- Monthly mean temperatures were extremely high from
northern Europe to northern Africa.
- Monthly mean temperatures were extremely low in western
Europe and monthly precipitation amounts were
extremely heavy from eastern to western Europe.
- Monthly precipitation amounts were extremely heavy in the
central USA.
Extratropics:
In the 500-hPa height field, wave trains were observed
along the polar-front jet stream (Fig. 5) from the Atlantic to
Eurasia (Fig. 4). In association, the jet stream shifted
southward of its normal position in western Europe, bringing
lower-than-normal temperatures, and shifted northward of its
normal position in western Russia, bringing
higher-than-normal temperatures. A ridge was seen over East
Asia, and a trough was seen to the east of Japan. A blocking
ridge developed around the Kamchatka Peninsula.
Tropics:
Convective activity was enhanced over the North Indian
Ocean and south of Indonesia, and was suppressed around
the equatorial date line region (Fig. 6). The active phase of
the Madden-Julian Oscillation propagated eastward from the
Indian Ocean to the western Pacific in the first half of the
month (Fig. 7). In the equatorial lower troposphere, westerly
and easterly wind anomalies were seen from the Indian
Ocean to the Maritime Continent and over the Pacific,
respectively (Fig. 7). In the upper troposphere, wave trains
were observed along the subtropical jet stream over southern
Eurasia with anticyclonic circulation anomalies over
northwestern India (Fig. 8). The Southern Oscillation Index
value was +1.0 (Fig. 10).
Oceanographic Conditions:
In the equatorial Pacific, remarkably negative SST
anomalies were seen in the eastern part. The monthly mean
SST anomaly and the SST deviation from the latest sliding
30-year mean in the NINO.3 region were both -0.8°C. In the
North Pacific, remarkably positive SST anomalies were seen
south of Alaska, from near Hawaii to around 15˚N, 175˚W
and from the South China Sea to the east of the Philippines.
Remarkably negative SST anomalies were seen south of
Japan.
In the Indian Ocean, negative SST anomalies were seen
west of 85˚E mostly and positive SST anomalies were seen
east of 85˚E in the equatorial area. Remarkably negative SST
anomalies were seen near the northeastern coast of
Madagascar, remarkably positive SST anomalies were seen
from near the northwestern coast of Australia to south of
Sumatra. In the North Atlantic, remarkably negative
anomalies were seen from around 20˚N, 60˚W to around
35˚N, 40˚W, surrounded by the remarkably positive SST
anomalies seen from near the western coast of North Africa
to around 15˚N, 45˚W and from near the eastern coast of the
USA to south of Greenland.
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14 June 2013
Japan Meteorological Agency
Fig. 1 Monthly climate anomaly / ratio over Japan
(May 2013)
Top: temperature anomalies (degree C)
Middle: precipitation ratio (%)
Bottom: sunshine duration ratio (%)
Anomalies are defined as the deviations from the normal
(1981-2010 average).
Fig. 2 Long-term change in monthly anomalies of
global average surface temperature in May
The thin black line indicates anomalies of the surface
temperature in each year. The blue line indicates five-year
running mean, and the red line indicates a long-term linear
trend. Anomalies are deviations from the 1981-2010
average.
Fig. 3
Distribution of extreme climate events (May 2013)
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14 June 2013
Japan Meteorological Agency
Fig. 5 Monthly mean 200-hPa wind speed and
vectors in the Northern Hemisphere (May 2013)
Fig. 4
Monthly mean 500-hPa height and anomaly in
the Northern Hemisphere (May 2013)
The contours show heights at intervals of 60 m. The
shading indicates height anomalies. The base period for the
normal is 1981-2010.
Fig. 6
The black lines show wind speeds at intervals of 10 m/s.
The dark blue shading shows values greater than 20 m/s.
The green lines show normal wind speeds at intervals of 20
m/s. The base period for the normal is 1981-2010.
Monthly mean Outgoing Longwave Radiation (OLR) anomaly (May 2013)
The contour interval is 10 W/m2. The base period for the normal is 1981-2010. Original data provided by NOAA.
Fig. 7
Time-Longitude cross section (5°N-5°S) of five-day mean 200-hPa velocity potential anomaly (left) and
850-hPa zonal wind anomaly (right) (December 2012 - May 2013)
The contour intervals are 2x106 m2/s (left) and 2 m/s (right). The base period for the normal is 1981-2010.
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14 June 2013
Fig. 8
Japan Meteorological Agency
Monthly mean 200-hPa stream function and anomaly (May 2013)
The contour interval is 10x106 m2/s. The base period for the normal is 1981-2010.
Fig. 9
Monthly mean sea surface temperature anomaly (May 2013)
The contour interval is 0.5 degree C. The base period for the normal is 1981-2010. Maximum coverage with sea ice is shaded in gray.
Fig. 10 Time series of monthly mean SST departure (degree C) from the reference value defined as the
immediate past 30-year mean SST averaged over the NINO.3 region (upper). Time series of the Southern
Oscillation Index with respect to the 1981-2010 base period (lower).
Thin blue lines represent monthly means and thick blue lines five-month running means. Periods of El Niño and La Niña events are
shown as red-colored and blue-colored boxes, respectively.
Detailed information on the climate system is available on the Tokyo Climate Center's website.
http://ds.data.jma.go.jp/tcc/tcc/index.html
This report is prepared by the Climate Prediction Division, Global Environment and Marine Department, Japan Meteorological
Agency.
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