| There are many unique features in the tropical Indian Ocean, compared with the tropical Pacific or Atlantic. Based on the observation data such as COADS and SODA, the main climatological features of the tropical Indian Ocean and relationships of sea surface temperature (SST), heat budget with ocean dynamics and thermodynamics processes are analyzed; the seasonal and interannual variability of the tropical Indian Ocean are well simulated using a ocean general circulation model; Based on the thermal equation and model output data, the variation mechanism of SST and heat budget are investigated in the tropical Indian Ocean; Besides, the effect of seasonal variation of wind stress, Ekman pumping and horizontal diffusivity on the ocean current and heat budget are studied, using both ideal model and complex model.The tropical Indian Ocean, especially for the region north of 7, is strongly influenced by Asia monsoon. In response to the seasonal reversal of wind, ocean currents also show obvious seasonal reversal with Somali current most prominent. Besides, the strong upwelling appears along the Somali-Arabian coast in summer but downwelling in winter, the southward cross-equator Ekman transport occurs in summer but opposite in winter. Further more, the SST warming twice in one year in the northern Indian Ocean, the mixed layer deepening in the central Arabian Sea during summer, as well as the equator jet occurred only in transient seasons are all noteworthy. The wind in summer dominates other seasons with annual mean westerly on the equator. In addition, the wind stress near the equator basically changes from west to east, resulting in southward Ekman transport on both sizes of the equator. Those unique dynamics have significant effects on the heat budget and SST of the northern Indian Ocean. The correlation analysis between SST and sea surface height, heat content and depth of thermocline also shows the important role of ocean dynamic processes in some regions, besides the influence of heat exchange between air and sea.Based on the equation of temperature in mixed layer, combined with the data from an ocean model, the relative important of different processes in controlling the SST variations are determined. For the northern I ndian Ocean, the net surface heat flux and entrainment through the bottom of mixed layer have semiannual period, which is the major cause of semiannual variations in SST. In boreal summer, the entrainment dominates the western part of Bay of Bengal and most part of Arabian coast; net surface heat flux is always a dominant factor controlling the SST variation in Bay of Bengal throughout a year. Difference physical processes control the temperature of the mixed layer in different regions.The quantitatively studies of the heat budget in the northern Indian Ocean are given, focusing on the heat transport and the mechanisms involved in, based on the heat budget equation and data from the ocean model. It is showed that the heat transport crossing the equator has the similar magnitude and the same period of one year, compared with that of 10°N in Arabian Sea. By contrast, the heat transport across 10°N in Bay of Bengal has a much smaller value with a prominent semiannual period; There are tight relationship between integrated zonal wind stress in one latitude of the Indian Ocean north of 7°N and the total heat transport across that latitude, as well as the total net surface heat flux north of that latitude. The maximum correlation coefficient is less than -0.5. The heat transport concentrated on upper 500m, especially upper 150m; Of the total transport, the contribution from the meridional overturning circulation is overwhelming. All these results confirm the important of wind in meridional circulation and heat transport.Based on MOM2 model, a rectangular basin model with ideal w ind stress and other ideal conditions is designed to study the main processes and dynamical mechanism in setting the depth of cross-equator flow. The effects of horizontal diffusivity, seasonal variations of...
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