Highlights
General
Circulation Features
Northern
Hemisphere
During June, at the mean 500hPa geopotential height field
over the mid-high latitudes, meridional circulation prevailed over the Eastern
Hemisphere and zonal circulation dominated the Western Hemisphere. A strong ridge
covered central and southern Europe, with the maximum positive
anomalies above 8 dam. Meanwhile, a
deep trough dominated Eastern Europe, with the center value below –12 dam. In addition, negative anomalies
less than –8 dam covered the
northeastern Atlantic. The Northwest Pacific subtropical high was obviously
stronger than normal and its position shifted westward.
Southern
Hemisphere
During the
month, at the
mean 500hPa geopotential height field, zonal circulation prevailed over the
mid-high latitudes, while meridional circulation obviously controlled the
southeastern Pacific. In the
height anomaly
field, positive anomalies were over most of the mid-high latitudes, with
the maximum above 16 dam over part of Antarctica. Meanwhile, negative anomalies
covered the southeastern Pacific
and the region south to Australia,
with
the center value below –8
dam.
In June, monthly mean surface air temperatures were
near or above normal in most of China, with 2~4°C above normal
in eastern Xinjiang. Temperatures were slightly below normal in most of North China, South China and most of Southwest China.
As to
precipitation, rainfall totals were near or more than normal in most of China,
with 30~100% more than normal in southern Northeast China, the Great Bend of
the Yellow River, the region between the Yellow River and the Huaihe River, the area between the Huaihe River
and the Yangtze River, part of
Southwest China, southern Xinjiang, southern Guangdong and southern Guangxi. Meanwhile,
rainfall totals of 30~80% less than normal were observed in central-eastern
Heilongjiang, part of East China and northern Xinjiang.
Sea
Surface Temperatures (SSTs)
During June, the situation of rapid cooling trend of sea
surface temperatures in the central and eastern equatorial Pacific reversed,
and negative SST anomalies reduced greatly. SST anomalies
below –0.5℃ controlled the region east to 140°W, with the center value below –1.5℃. Correspondingly,
the SST indices of NINO 4, NINO 3 and NINO 1+2 were 0.4℃, –0.5℃ and –1.5℃, which rose
0.1℃, 0.4℃ and 0.2℃ from last month, respectively. In addition, positive
SST anomalies of 0.5~1.0°C were observed in most of the equatorial
Indian Ocean.
Circulation
Wind
Field
In this month, at the lower
troposphere (850hPa), weak westerly anomalies covered the equatorial Pacific.
Easterly anomalies of 4~6 m/s were over most of the equatorial Indian Ocean. At the upper troposphere (200hPa), winds
were near normal over the central and western equatorial Pacific, and weak easterly
anomalies controlled the eastern equatorial Pacific. Meanwhile, weak westerly
anomalies were over the equatorial Indian Ocean.
Southern
Oscillation
The Southern
Oscillation Index (SOI) was –1.0.
Convection over the Tropics
During June, the anomalous outgoing longwave radiation (OLR)
distribution displayed that convections were near normal over the eastern equatorial
Pacific, while convections were generally suppressed over the central and western equatorial
Pacific. In the lower troposphere (850hPa) divergent wind field, there wasn’t
any obvious convergent center over the tropical Pacific, and a divergent center
was around 95°W nearby the equator. At the upper troposphere
(200hPa), two divergent centers were around 95°E, 23°N and 120°E, 22°N, respectively. The convergent center was
around 105°W, 15°S.