COMPARISON OF THE CORRELATIONS OF LOWER TROPOSPHERIC CIRCULATION WITH TROPICAL AND EXTRATROPICAL SEA SURFACE TEMPERATURE ANOMALIES

The method of rotational principle component (RPC) was employed to analyse the sea surface temperature (SST) in the area of the Indian Ocean and western Pacific Ocean in the 105-month period from January 1980 to September 1988. A tropical mode Et,of SSt anomaly (SSTA) centered to the east of the Philippines and an extratropical mode Et,of SSTA in the surroundings of the Kamchatka Peninsula were thus obtained. The monthly mean meteorological fields at 850hPa in the same 105-month period were then projected onto the time eigenvectors of these two modes respectively to compare their relations with SSTA at different latitudes.Results show that in both tropical and extratropical regions,warm SSTA is accompanied by positive anomaly of specific humidity at 850hPa.and by abnormal convergence of mean flux of monthly averaged specific humidity.Moreover,the statistically significant correlations of the 850hPa fields were found just above the SSTA region or its neighbourhoods.The main differences between the two sets of projection were found in the 850hPa fields of flow,geopotential height,and temperature.Related to the tropical positive SSTA are lower height,colder temperature anomalies,and accompanied with the Gill type cyclonic abnormal circulation.On the contrary,over the extratropical positive SSTA.positive height and temperature anomalies.and a strong anomalous anticyclonic circulation appear.Diagnoses showed that such remarkable differences are mainly due to the strong geostrophy and baroclinity of the atmosphere at high latitudes.