East Asia and Western Pacific METEOROLOGY AND CLIMATE

INTERAiWAL VARIABILITIES OF THE WESTERN TROPICAL
PACIFIC OCEAN AND LOW-FREQUENCY RESPONSE
OF THE SUBTROPICAL HIGH OVER THE NORTHWEST PACIFIC OCEAN
375
Pu Shuzhen
Yu Huiling
First Institute of Oceanography, SOA, Qingdao, China
ABSTRACT
Computation and analysis of the interannnal variabilitiesof the area,
strength,and westward extention of the snbtropical High over the Northwest
Pacific Ocean (NWPQ) are made to show that the variabilities, with a phase
lag, are correlated to the El Nino events. In order to explain the
correlation between the two, data obtained by the Sino-Acierican bilateral
TOGA Program are used to find scientific evidences for the interannnal
variabilities of the thermal structure and circulation in the upper Western
Tropical Pacific Ocean (WTPQ) and to discuss their effects on the subtropical
High over the NWPO, It is found that the WTPO features daring the 1986/1987
El
Nino event are obviously different from those before or after the event.
The main variabilities in the WTPO during the El Nino event, which lay
affect the snbtropical High over the NWPO, are as follows: (1) east-west
spreading along the equator of the warmer water in the waning pool; (2)
decrease of the northward transportation of the warmer water from the
area (south of 18° N, west of 130° E) where the Inroshio originates, The
former could anomalously heat the atmosphere over the Western Equatorial
Pacific Ocean(WEPO),and the latter could decrease the heat content in the
upper water under the subtropical High-over theJWPO, The both will drive
the
and
Hadley circulation in the related longitudes running faster than normal
strenghen the downward motion in the upper air and the divergence in the
lower level of the subtropical High over the NWPQ*Therefore, the subtropical
High over theJfWPO becomes stronger and larger than normal.