East Asia and Western Pacific METEOROLOGY AND CLIMATE

the NWPO and the data obtained from the Sino-American bilateral TOGA program
seems to allow to draw the following conclusions'
(1) the strength, area and westward extension of the subtropical High over
the NWPO show interannual variabilities obviously related to El Nino events in
the equatorial ocean, and with a time-lag about 3~4 months;
(2) During the 1986/1987 El Nino event, warmer water in the wanning pool in
the WTPO spreads more east-westward, making the Hadley Circulation over the WTPO
run faster. The speeded Hadley Circulation then brings absolute angular momentum
to the poleward area from the equator at a higher rate than normal and then
downward to the surface north of the equatorial easterlies. The effects are
reflected by the larger and stronger subtropical High over the NWPO;
(3) In an El Nino event ( at least in the last stage), the heat transported
by the western boundary current to the subtropical NWPO obviously decreases,
which then reduces the heat content of the upper NWPO where the boundary current
flows, the changing tends to strenthen both the downward motion and flow
divergence in the lower atmosphere of the subtropical High over the NWPO. This
could be the additional mechanism for the strengthening of the subtropical High
over the WTPO, makes it occuping more area, and extending further westward
during an El Nino event than normal.
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AdNOwIEDGEMENTS
The authors wish to take this chance to thank both SOA and NOAA which are
supporting the China and American bilateral TOGA program. We are grateful to Drs.
B.Taft 1 , M.Mcphaden 1 , L.Mangum 1 , J.Tooie 2 , KX.Miilard 2 and E.Firing 3 and other
U.S. col leagues, and Z.Wang 4 , Ou 4 , B.Li 4 and other Chinese colleagues of
for their scientific contribution to the program.
1. Pacific Marine Environmental Laboratory, Seattle, Washington U.S.A.
2. Woods Hole Oceanographlc Institution, Woods Hole, Massachusetle, U.S.A.
3. JIMAR, University of Hawaii, Honolulu, U.S.A.
4. First Institute of Oceanography, Qingdao, China.
ours
REFERENCE
(1). Bjerknes, J., A Possible Response of the Atmospheric Hadley Circulation to
Equatorial Anomalies of Ocean Temperature, Tellus, 18(1966),820-829.
(2). Pu Shuzhen and Yu Bulling, Characteristics of Frequency Response Between