Climate
in China
During August,
monthly mean surface air temperatures were 1~2℃
below normal in western part of the region between the Yellow River and the
Huaihe River, the Hanshui River Valley, the Sichuan Basin, northern Hunan and
western Xinjiang, while temperatures were about 2℃ above normal in
the east-central and southern Tibetan Plateau, east-central Inner Mongolia,
northwestern Heilongjiang. Precipitations were more than 30% above average in
much of the regions between the Yangtze River and the Yellow River, the eastern
and mid-northern Tibetan Plateau, northern and southeastern Xinjiang, with
maximum above 400%. Meanwhile, precipitations were less than 30% in northeastern
Northwest China, east-central Inner Mongolia, western and northern Heilongjiang,
most of the regions south to the Yangtze River and the western Tibetan Plateau.
Climate
in the World
During August,
monthly mean surface air temperatures were observed 1~2℃
below normal in southwestern Europe, parts of middle Asia, regions north to the Central Siberian Plateau,
central China and southernmost South America. Meanwhile,
temperatures
were near or above normal in the rest regions, with 1~2℃
above normal in
northeastern and southeastern Europe, Mongolia and the nearby regions, northwestern
and eastern North America and eastern South America, and
central value above 3℃
in eastern South America.
During August,
precipitations were more than 50% above average in southeastern Europe, regions
from middle Asia to Northwest China, parts of southeastern Russia, mid-southern
part of the United States, southern South America, west-central and northeastern
Australia. Meanwhile, precipitations were 50% below normal in parts of
northeastern Europe, northern East Asia, northern South Asia, middle of West
Africa, South Africa, mid-western North America, middle South America and
mid-southern Australia.
3.
General Circulation Features
Northern Hemisphere: During August, in the 500hPa
geopotential height anomaly field at the mid-high latitudes,
positive anomalies above 4 dam were over the northeastern Pacific, northeastern
Europe, regions from the Polar Regions to the Bering Sea and parts of the
northeastern Pacific Ocean. Negative anomalies below -4 dam were over parts of
the northern North Atlantic Ocean and the central Siberia Plateau. For the
month, subtropical highs in northern hemisphere and the Northwest Pacific were
larger and stronger than normal, and the ridge line of the Northwest Pacific
subtropical high located northward than normal.
Southern Hemisphere:
During August, the
mean 500hPa geopotential height field exhibited a 3-wave pattern at the mid-high
latitudes. In the height anomaly field, negative anomalies below -4 dam were
over the eastern South Pacific, regions south to both Australia and Africa with
central value below –12 dam. Meanwhile, positive anomalies above 4 dam covered
the central and western South Pacific and the western South Atlantic Ocean, with
maximum above 12 dam in the central and western South Pacific Ocean.
4、 Tropical
Features
Sea
Surface Temperatures (SSTs): During August, SSTs over the east-central equatorial
Pacific were near normal. Positive anomalies above 0.5℃
dominated the region west to the date line. Compared with last month, while SSTA
index of NINO1+2 increased from –0.7 to –0.2, indices of NINO 3, NINO 4,
Nino 3.4 and NINO Z were 0.2℃, 0.4℃, 0.2℃ and 0.3℃ with slightly
decreases. Meanwhile, positive anomalies were about 0.5℃ over the
equatorial Indian Ocean.
Subsurface
Temperatures: During August, weak positive anomalies of subsurface Ocean temperatures
remained in the western Pacific. Abnormally subsurface cold water in the
east-central Pacific east to 160ºW
generally enhanced with center value below –2℃,
while subsurface cold water weakened in
the offshore of South America compared with last month .
Warm
Pools: During August, the warm pools in the western Pacific and in the Indian
Ocean were both larger than normal in area and stronger than normal in
intensity.
Wind Field：During August, at the lower troposphere (850hPa), zonal winds were near normal over most of the equatorial Pacific and the Indian Ocean. At the upper troposphere (200hPa), easterly anomalies were over most of the east-central equatorial Pacific and zonal winds over the western Pacific and the Indian Ocean were near normal.
Southern Oscillation：During August, Southern Oscillation Index (SOI) was -0.5, with a drop of 0.5 since last month.
Convection
over the Tropics: For the month, the anomalous outgoing longwave radiation (OLR) showed that
convections over Pacific were near normal. In
the lower troposphere (850hPa) divergent wind field, no convergent center was
over tropical Pacific, and a divergent center was over near 72.5ºW,
27.5ºS. Correspondingly, at the
upper troposphere (200hPa), a divergent center was over 117.5ºE, 17.5ºN, and a convergent center was observed over 77.5ºW,
22.5ºS.
5. ENSO
Monitoring and Forecasting
①
During August, SSTs over
the east-central equatorial Pacific were near normal.
②
Weak positive anomalies of subsurface Ocean temperatures remained in the
western Pacific and abnormally subsurface cold water in the east-central Pacific
east to 160ºW generally enhanced.
③ The Southern Oscillation Index (SOI) was -0.5.
④
At the lower troposphere
(850hPa), zonal winds were near normal in the equatorial Pacific and the
equatorial Indian Ocean. Convections
were near normal in the equatorial Pacific.
⑤
Forecasts of most statistical and coupled models for ENSO
show that SSTA index for NINO3 will be near normal in the following 3 months.
Above results show that generally tropical atmospheric and oceanic conditions were near normal in August and ENSO cycle will likely be neutral in following months. The evolution will be monitored carefully and continuously.