During
October, monthly mean surface air temperatures were near or below normal in most
of China, with more than 1¡æ
below average in Sichuan,
Guizhou and Fujian.
Only in Northeast China,
temperatures were
more than 2¡æ
above average. For the month, rainfall totals were 50-100%
below normal in most of China and no precipitation was received in South China,
central Northwest China and northeastern Inner Mongolia. Meanwhile, rainfall
totals were 50% above normal in eastern Tibet and eastern Qinghai, with 2-4
times more than normal in some local regions.
Monthly
mean surface air temperatures were 1-3¡æ
below average in most of East Siberia, western South Asia and
central China. Meanwhile temperatures were near or above normal in the other
regions, with about 2~4¡æ
above average along the coasts of Mediterranean Sea, from southern West Siberia
to Northeast China, from eastern East Siberia to Alaska, in southeastern USA and
most of Australia.
For
the month, rainfall totals were more than 50% above normal in most of USA, the
east coast of Australia, western Europe, the regions from Kazakhstan to western
West Siberia Plain, southern Mid Siberia and the regions from southern Tibet to
the Bay of Bengal,
and even two times more than normal in local regions. Rainfall totals were about
50-100% less than normal in most of East Asia, mid-western South Asia, most of
Australia and the coasts of Mediterranean Sea.
Northern
Hemisphere: In October,
the mean 500hPa
geopotential height field exhibited a four-wave pattern at the mid-high
latitudes. In the height anomaly field, the areas from northern Asia to western
North America and from the central Atlantic to western Europe were covered by
negative anomalies, with central values below ¨C12 dam near Ireland. Meanwhile,
most of the other regions in the mid-high latitudes were dominated by positive
anomalies, with the central values above 16 dam near south of Greenland. The
Northwest Pacific subtropical high was smaller and slightly weaker than normal,
and extended westward
obviously.
Southern
Hemisphere: For the month at the mean 500hPa geopotential height field, zonal
circulation prevailed the mid-high latitudes. Negative anomalies below ¨C4 dam
covered the southern Pacific around the date line. Meanwhile, heights in the
other regions were near or above normal. Positive departures above 4 dam covered
much of the polar region, with central values above 12 dam.
Sea
Surface Temperatures (SSTs): During
October, above 0.5¡æ
SST anomalies dominated the central and eastern equatorial Pacific, with central
values above 1.5¡æ
around the date line. SSTs in the eastern equatorial Pacific increased
remarkably and weak negative SST anomalies disappeared in much of the offshore
of South America. Weak negative SST anomalies controlled the west part of the
western equatorial Pacific while above 0.5¡æ
SST anomalies maintained in the equatorial Indian Ocean. Correspondingly, the
SST indices of NINO 4, NINO 3, NINO 1+2 and NINO Z were 1.1¡æ,
0.4¡æ,
0¡æand
0.7¡æ,
respectively.
Subsurface
Temperatures: During
October, the abnormally warm water weakened remarkably in the equatorial Pacific
and moved up in the eastern equatorial Pacific.
Warm
Pools: In
October, the area of the western equatorial Pacific warm pool was slightly
larger than normal, and its intensity weakened compared with last month. The
area of the equatorial Indian Ocean warm pool was near normal and its intensity
was slightly stronger than normal.
Wind
Field: In
this month, at the lower troposphere (850hPa), westerly anomalies controlled
most of the equatorial Pacific except that weak easterly anomalies maintained in
the eastern equatorial Pacific. The westerly anomalies over the western
equatorial Pacific markedly strengthened with the central value above 4m/s.
Easterly anomalies still controlled the equatorial Indian Ocean. At the upper
troposphere (200hPa), easterly anomalies covered most of the equatorial Pacific
while westerly anomalies controlled the equatorial Indian Ocean.
Southern
Oscillation:
During October, the Southern Oscillation Index was ¨C0.1.
Convection
over the Tropics: For
the month, the anomalous outgoing longwave radiation (OLR) distribution
exhibited that the active convections over the western equatorial Pacific
withdrew eastward and the convections were suppressed over Indonesia. In the
lower troposphere (850hPa) divergent wind field, the convergent center was near
165¡ãE
over the equator and the divergent center was around 108¡ãW,
12¡ãS.
Correspondingly, at the upper troposphere (200hPa), the divergent center was
near 165¡ãE
over the equator, and the convergent center was over 115¡ãW,
15¡ãS.
a)
During October,
above 0.5¡æ
SST anomalies dominated the central and eastern equatorial Pacific. SSTs in the
eastern equatorial Pacific increased remarkably and weak negative SST anomalies
disappeared in much of the offshore of South America.
b)
In this month,
abnormally high sub-surface temperatures weakened in the central equatorial
Pacific and moved up in the eastern equatorial Pacific.
c)
The Southern
Oscillation Index remained weak negative value.
d)
At the lower
troposphere (850hPa), westerly anomalies kept controlling most of the equatorial
Pacific and markedly strengthened over the western equatorial Pacific.
e)
The
active convections over the western equatorial Pacific withdrew eastward and the
convections were suppressed over Indonesia.
Recent
oceanic and atmospheric status in the tropical
Pacific showed that El Nino conditions sustained and the current
situation is in favor of the development of ENSO warm-episode.