Highlights
General Circulation Features
Northern Hemisphere
During
January, the
mean 500hPa geopotential height fields exhibited a 4-wave pattern in the
mid-high latitudes. The trough over East Asia was deeper than normal. In
the height anomaly field, negative anomalies were over the
northeastern Pacific,
eastern North America
and northwestern Europe, with center values
below –12, –8
and –8
dam, respectively. Meanwhile, positive
anomalies controlled most of mid-southern
Asia and western North America,
and the center value of the later was 8 dam above normal. The
Northwest Pacific subtropical high was obviously stronger than normal and its
position shifted westward.
Southern Hemisphere
During
the month, in the
mean 500hPa geopotential height
fields， zonal
circulation prevailed over the mid-high latitudes. In the height anomaly
field, positive anomalies were over most of
Southern Hemisphere, with
the maximum above 8 dam over the part of Antarctica. Meanwhile, negative
anomalies covered the
southeastern
Atlantic and southeastern Pacific,
with
the minimum below –4
dam.
In
January, monthly mean surface
air temperatures were near or above normal in
most of China. Temperatures of 2~3°C
above normal were observed in most of Northeast China, the mid-northern Tibetan Plateau, most of northern Xinjiang and
eastern Inner Mongolia. Temperatures
were 1°C
below normal in
eastern and central Xinjiang,
northeastern Yunnan and northern Shanxi.
As
to precipitation, precipitation totals of 50% less than normal were received in
southern Xinjiang, most of Qinghai, mid-southern North China, central Sichuan
and part of Inner Mongolia. Monthly
precipitation totals were 30~100% above normal in most of China. There were
three times more than normal in part of Xinjiang, Tibet and Yunnan.
Sea Surface Temperatures (SSTs)
During
January, positive SST anomalies of 0.5°C
remained in the central and eastern equatorial Pacific, with the maximum
above 2.0°C.
Meanwhile, negative
SST anomalies appeared in the
offshore of South America. Correspondingly,
the SST indices of NINO 3 and NINO 1+2 were 0.8 and –0.2,
which dropped sharply from 1.4 and 0.5 in last month, respectively. In addition,
positive SST anomalies above 0.5°C
were observed in most of the equatorial Indian Ocean.
Circulation
Wind Field
In
this month, at the lower troposphere (850hPa), westerly anomalies of 2~4 m/s
covered the most of the equatorial Pacific. Westerly anomalies about 2 m/s were
over the equatorial Indian
Ocean. At the upper
troposphere (200hPa), easterly anomalies of 4~8 m/s maintained over the central equatorial
Pacific and weakened obviously over the eastern equatorial Pacific. Weak
westerly anomalies controlled the western equatorial Pacific and eastern
equatorial Indian Ocean. Meanwhile, westerly anomalies of 4~8 m/s were over the
western equatorial Indian Ocean.
Southern Oscillation
The
Southern Oscillation Index (SOI)
was –0.1.
Convection over the Tropics
During January,
the anomalous outgoing longwave radiation (OLR) distribution displayed that the
obviously convections enhanced nearby the dateline over the equatorial Pacific
and its position
shifted westward obviously. Suppressed convection weakened was over western Indonesia.
In the lower troposphere (850hPa) divergent wind field, a convergent center was
nearby 135°E,
10°S,
and a divergent center was around 95°W
nearby the equator. Correspondingly, at the upper troposphere (200hPa), the
divergent and the convergent centers were around 135°E,
10°S
and 90°W,
10°S,
respectively.