THE INTRASEASONAL VARIABILITY OF SURFACE WIND AND UPPER LAYER THERMAL STRUCTURE IN THE WESTERN TROPICAL PACIFIC WARM POOL REGION DURING THE WINTER OF 1992～1993

Abstract:

In this paper, the hydrographical and meteorological data observed by the R/Vs "Xiang Yang Hong No. 5", "Experiment No. 3"and "Ke Xue No. 1 "during TOGA-COARE IOP are used to analyze the variability of surface wind and upper layer thermal structure, and to reveal the periods of intraseasonal oscillation of surface wind components and certain layers of sea temperature from November 6, 1992 to February 18, 1993 in the western tropical Pacific warm pool region. It is shown that the variation of the sea surface temperature (SST) was inversely correlated to that of surface wind components. It is also indicated from spectral analysis that the significant periods of intraseasonal oscillation of daily mean zonal wind (MZW) were 30-to 60-day and 8-to 9-day long, and that of mean meridional wind (MMW)was 6-to 7-day long. The fluctuation of daily mean sea temperature (MST) in certain layers from surface to the 250 m layer also had the 30-to 60-day low frequency oscillation except for the 150 m layer,and the fluctuations of the daily MST in 100, 150, 200 and 250 m layers had the same 3-day period,their coherence and phase differences were over 0. 90 and between 319° and 353° respectively, which implies the fluctuations of daily MST from 100 to 250 m layers were in phase with each other in the same 3-day period. The analysis of in situ observations revealed a physical evidence of the westerly wind bursts (WWBs) which trigger off the eastward movement of warm water through intraseasonal oscillation and induce the onset of E1 Nino event.