Multiple Time Scale Analysis Of The SST In The Seychelles Dome Region Of The Indian Ocean

Based on ORA-S3 data from January 1959 to December 2008, multiple time scales (annual, seasonal variation and interannual variability) of the sea surface temperature (SST) in the Seychelles Dome (SD) region of the Indian Ocean are studied. Then related mechanisms are investigated by using the correlation analysis, synthesis analysis and the temperature balance of the mixed layer. The main conclusions are as follows:(1) SST variation in the SDOn the annual mean scale, the isotherm is northwest-southeast. SST is warm (cold) in northeast (southwest) of SD, and cold centers exhibit.On the seasonal scale, SST warms from January to April (warmest), and cools from May to August (coldest), then warms from September to December. On the horizontal distribution, the SST in SD exhibit low centers as thermocline depth in January to March. The isotherm is parallel to latitude, and is the same as the annual mean scale.On the interannual time scale, most years of positive (negative) SST anomaly in autumn-winter and spring next year are correspond to El Nino(La Nifia) years and positive (negative) Indian Ocean dipole years, with some exceptions especially in summer. Composite analysis shows that the magnitude of SST anomaly is maximum in February and minimum in August respectively, while the spatial pattern with closed low center is most obvious in May.(2) The main related mechanisms of SSTThe main results of the correlation analysis and synthesis analysis shows that there are many factors influencing the interannual variability of the SST in SD, and the processes have evident seasonality. The thermocline depth can affect SST in January to July by a lead of 4-7 months (positive correlation). The wind stress causes variations of SST though Ekman pumping, evaporation and Ekman transport, where the Ekman pumping affects SST in December to June with a time lead (in which the term of wind stress curl is dominate), while the effect of the magnitude of wind stress is similar with negative correlation but with no time lead. Indonesia throughflow (ITF) can influence SST in each month; especially the volume transport of ITF in May (November) has an obvious positive correlation with the SST in May to December (in November to first half of the next year).The main results of the mixed layer heat budget:On the annual mean scale, the net surface heat flux term and horizontal advection term is positive in SD, while the entrainment is negative. The balance between these terms is the main physical process of the annual mean SST in SD.On the seasonal scale, the temperature trendency term shows semiannual signal. The seasonal variation of the net surface heat flux term is same with the temperature trendency term, which means it plays the most important in the seasonal variation of SST in SD. But it is the most important physical processes only from January to March, June to July and from October to December. The horizontal advection term plays the most important roles from August to September. The entrainment is bigger or appropriate with the net surface heat flux term.On the interannual time scale, different physical processes also show significant seasonal differences in SD region. The net surface heat flux term plays the most important role in the interannual variability of SST from Februray to March and September to December. The entrainment trem plays the most important role in January and April to June. The horizontal advection term plays the most important roles from July to August.