Presenter: Chihiro MIYAZAKI
In order to investigate the interannual variation of winter surface
temperature in Asia at from middle to lower latitudes, EOF analysis
was applied to standardized monthly surface temperature (Nov. - Mar.)
from 1979/80 to 2002/03. The analyzed area is 40E - 160E and 60N - 10S.
As a result, four principal components are adopted. The first component
means the temperature contrast in the north/south of Tibetan Plateau.
From the synoptic composite analysis of the 7 highest and the 7 lowest
scores, this component coincide AO and NAO. On the second component,
strength/weakness of the Siberian High is dominant. Especially, cold
anomaly at the former half of 1980s is significant. The third component
shows the temperature contrast between tropical western Pacific and the
two areas of southern Japan and Arabian Sea. This component has relation
to ENSO. The forth component denotes the signal of surrounded area of
Tibetan Plateau and the opposite signs in the north and south of the
plateau. This component seems to be influenced by the Plateau.
Presenter: Hatsuki FUJINAMI
In order to understand the relationship between the seasonal variation of
the surface condition and that in the atmospheric boundary layer (ABL),
an intensive observation was carried out during before and after Meiyu
season of 2004 at Shouxian (China). In 2004 summer, Meiyu front did not
appear continuously. Onset of the Meiyu was also ambiguous. Surface specific
humidity, however, increased abruptly after around 14th June around Shouxian,
and then large amount of the moisture is observed continuously. The rapid
increase of specific humidity is associated with the passage of an eastward-moving
disturbance (not Meiyu front). Around same time, surface vegetation changed
into paddy fields. After that, atmospheric stratification became more unstable
for moist convection. I'll report characteristics of seasonal variation in cloud
activity and associated atmospheric structure during 2004 summer.
Presenter: Prasanna Venkatraman
This paper investigates the seasonal march of the summer monsoon
through several different sub-divisions of the Asian monsoon
region. Five data sets, the Climate Prediction Center (CPC) Merged
Analysis of Precipitation(CMAP), the upper-tropospheric water vapour
band Brightness Temperature (BT), the Outgoing Longwave Radiation(OLR),
the lower tropospheric wind and Korean daily rainfall for 1980-1995, are
used. Analysis shows that the largest area of deep convection in the
global atmosphere is located over the tropical Indian Ocean-equatorial
western Pacific; its centre being positioned 110°E along the
equator in boreal winter and then moves northwestward to 80°E at
5°N in late July. In late April, the area of deep convection
first extends northward into the Indo-China Peninsula (ICP). In mid-May
it abruptly covers over the central South China Sea (SCS) region. After
the onset of SCS monsoon, deep convection starts to develop northward
along the eastern coast of China, East Tibet Plateau (ETP) and Indian
sub-continent, simultaneously. Based on the analysis of BT and
lower-tropospheric circulation, Asian summer monsoon can be divided into
six inter-linked sub-regional monsoons. They are Indo-China Peninsula
monsoon, SCS monsoon, South Asian (Indian) monsoon, ETP monsoon, East
Asian (south China, lower Yangtze River and Japan) monsoon and Northeast
Asian (north China and Korea) monsoon. In seasonal course, their onset
periods take place in late April - mid-May, mid-May, mid-May - late
July, mid-May - early June, mid-May - late June and late June - mid-July, respectively.
Presenter: Prasanna Venkatraman
Whereas some El Nino years are known to be associated with droughts in
some parts of the globe, notably India, other El Ninos do not seem to be
effective. Recently, it was observed that Unambiguous ENSOW (El Nino years,
in which the Southern Oscillation Index minima and Pacific sea surface
temperature maxima occurred in the middle of the calendar year) were better
associated with droughts. This association was checked for rainfalls in
South Asia and China. Singapore, Brunei, Indonesia and East Asia (comprising
of the People’s Republic of China and adjacent regions, including India)
showed a good association of Unambiguous ENSOW events with droughts.
Thailand, Malaysia and the whole Philippines showed some association; but
the northwest Philippines showed opposite results.
To find a rational for this criterion, it was checked whether such events
were in any way related to the timings of the El Nino events. In general,
El Ninos active during the main rainy season (June-September for all India's
summer monsoon rainfall) were better associated with droughts.
But some events did not fit this pattern. Also, many yearsnot having El Ninos
were associated with droughts. Thus, the El Nino relationship is not clear-cut
and predictions based on the same alone are likely to go wrong more often than
not, as in the case of the recent El Nino (1997).
Presenter: Manabu ABE
Because I would like to investigate vegetation's changes associated with
the climate change due to the uplift of the Tibetan Plateau, I have studied
the method to select new vegetation types.
I am going to introduce the rlated studies, and present my plan for
selection of vegetation types.
Presenter: Yoshiyuki KAJIKAWA
I'm studying the relationship between solar and monsoon activity
lately in cooperation with Dr. Fujita at Graduate School of
Environmental Studies. I'll introduce the short paper
"Solar influence on the Indian Ocean Monsoon
through dynamical processes"
By K. Kodera, Geophys. Res. Lett., accepted,
with the outline of our work in next Monsoon Saloon (Nov. 22).
This paper shows the interesting processes between solar and monsoon
activity in decadal time scale. That is, the solar influence on
monsoon activity is not due to a change in radiative heating
in the troposphere but originates from the stratosphere circulation
anomalies. I also intend to present some results of my analysis.
Presenter: Hiroki ICHIKAWA
The space-time characteristics of diurnal rainfall activity are investigated
over the Indonesian Maritime Continent by utilizing TRMM PR data for 5years. The prominent
diurnal cycle with distinct land-sea contrast are observed associated with complex sea-land
breeze and mountain-valley wind . Over Borneo and New Guinea, rainfall activity persists
until midnight from afternoon while Sumatra experience only a daytime rainfall. Over New
Guinea, stratiform rainfall exceed convective rainfall amount in nighttime hours.
The low level environmental flow influences the diurnal cycle of islands. Over Borneo,
rainfall activity exhibit a eastward (westward) propagation from midnight to morning during
westerly (easterly) over the whole island, which caused leeward enhancement in rainfall
amount. The advection in moist static instability can contribute to this island scale
propagation. The rainfall propagation is accompanied by strong convection, while the
characteristics of developed storm are different between land and sea region. The
propagation over the whole island observed in rainfall, unstable filed, and actual cloud
activity suggest that the island can form large atmospheric disturbance, which is flown to
east or west with containing local land-sea convection. Leeward propagation of convection
can be observed not only Borneo, but other around islands.
Presenter: Hiroki ICHIKAWA
Abstract: Diurnal variations of rainfall activity over Indonesian
Maritime Continent are examined by utilizing high resolutin TRMM PR
and GMS IR data. Large diurnal variations exist over islands and
their adjacent regions related to land-sea breeze and complex orograghy.
Over Borneo Island, rainfall activity show the eastward moving
on westerly day while the westward moving on easterly day after
midnight, which appeared most clearly over northern part as propagating
rainfall system which travel from the central mountain to adjacent
ocean at about 6-8m/s. These movements of rainfall activity cause
daily accumulated rainfall increase over leeward side of the island.
Same rainfall activity can be observed over Ner Guinea Island
though the influence is less than that over Borneo.The leeward
propagating cloud cluster exists not only Borneo Island but also
other small islands during eastward-propagatinting large disturbance passage.
Abstract: タイ北東部のKhon Kaenにおいて、水蒸気の観測を目的に、