East Asian Monsoon Monitoring Bulletin
No 2
2003. 6. 16
National Climate Centre/CMA
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South China Sea (SCS) summer monsoon occurs over southern SCS
in the 5th pentad of May, then breaks out over whole SCS in the 1st
pentad of June
The south China Sea (SCS) summer monsoon occurs over the
southern SCS in the 5th pentad of May, then it shifts northward and breaks
out over whole SCS in the 1st pentad of June.
The SCS high controlled the SCS in the 4th pentad of May (Fig.1).
During the 5th pentad of May, westerly prevailed the southern SCS as the
westerly eastward from the tropical Indian and cross-equatorial flow
nearby 105ºE reached 12ºN, but SCS high maintained over the northern
SCS (Fig.2). At the same time, the outgoing longwave radiation (OLR)
distribution displays that the center of convection located at 10ºN. Figure
4 shows the variation of the area-averaged (10-20ºN, 110-120ºE) zonal
winds, meridional winds and θse at 850hPa. It can be seen from figure 4
that the direction of wind changed to southwest and the values of θse
were larger than 340K steadily after the 5th pentad of May. These facts
indicate that SCS summer occurred over the southern SCS in the 5th
pentad of May. Southwestly moved northward obviously companied with
the convection northward in the 1st pentad of June (Fig.5), the entire
characteristic in the key region also exhibits distinct change at the same
time (Fig.4). In the 2nd pentad of June, Southwestly controlled the entire
SCS (Fig.6) associated with large area of strong convectivites (Fig.7).
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Figure 1 Pentad average 850hPa circulation of the 4th pentad of May 2003 (unit：m/s)
Figure 2 Pentad average 850hPa circulation of the 5th pentad of May 2003 (unit：m/s)
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Figure 3 Distribution of OLR in the 5th pentad of May (unit：W/m2)
Figure 4 Variation of pentad averaged zonal and meridionl wind and value between θ se
(potential pseudo-equivalent temperature) and 340K at the 850hPa over the area(10º
N-20ºN，110ºE-120ºE) from the 1st pentad of Jon 2003 to the 2nd pentad of June 2003
(Open circles denote zonal wind, solid line denote meridional wind and solid circles
denoteθse-340K)
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Figure 5 Pentad average 850hPa circulation of the 1st pentad of June 2003 (unit：
m/s)
Figure 6 Pentad average 850hPa circulation of the 2nd pentad of June 2003(unit：m/s)
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Figure 7
Distribution of OLR in the 2nd pentad of June (unit：W/m2)
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