热带印度洋MJO结构与SST季节内振荡及其年际变化

【作者】 李奎平；

【导师】 于卫东；

【作者基本信息】 国家海洋局第一海洋研究所 ， 物理海洋， 2008， 硕士

【摘要】 SST季节内振荡过程与大气MJO的结构密切相关。我们依据最新的卫星遥感资料和OAFlux热通量再分析资料,采用滞后相关方法,诊断了印度洋MJO的物理结构,得出了季节内振荡过程中海气通量和上层海洋变量(海表温度-SST、海洋混合层深度-MLD)的变化过程。然后通过选取印度洋锚定浮标捕获的季节内振荡过程,验证了以上的滞后相关分析的结果。研究结果很好地揭示了印度洋大气MJO的物理结构—在大气深对流中心,风速达到最大,潜热释放最大,同时到达海面的短波辐射最小。此类MJO结构造成的净热通量的季节内振幅最大,可引起最显著的SST季节内变化。海洋混合层的变化落后深对流30°位相,SST则落后深对流90°位相。为了检验SST、MLD的季节内变化与大气MJO过程的统一性,我们利用一维的PWP混合层模式,以上述分析的海气通量的振幅和位相关系为参考,模拟了SST和MLD的季节内变化过程,得出了与观测相符的结果。这同时检验了PWP模式在季节内振荡研究中的适应性,为下述利用此模式检验SST季节内振荡的控制机制奠定基础。SST季节内振荡存在明显的年际变化。我们从分析SST季节内振荡的控制机制出发,推测了其年际变化的调制因子。然后通过分析AVHRR SST资料、GODAS海洋温度场资料和OAFlux热通量资料,揭示了热通量和海洋次表层过程的年际变化对SST季节内振荡的影响。结果显示,热通量的年际变化对SST季节内振荡有存在很大影响,二者的振幅存在明显的正相关;而海洋次表层过程的年际变化在中南印度洋区域(温跃层较浅)对SST季节内振荡的影响最为明显,温跃层的变化与SST季节内振幅的变化呈负相关。对于以上提出的SST季节内振荡的年际变化机制,我们利用PWP混合层模式,通过设计数值实验,简要验证了我们的结论。更多还原

【Abstract】 The SST intraseasonal variability is closely associated with the structure of Madden-Julian oscillation(MJO).Based on the data from remote sensing,moored buoys and air-sea fluxes reanalysis system(OAFlux),lag correlation method is used to examine the physical structure of MJO in Indian Ocean.Composite analysis based on some MJO events captured by moored buoys shows a consistent result with the above research.This part provides a good phase relations among the surface air-sea fluxes and their coherent relationships with the variability of the upper ocean.Under the center of atmospheric deep convection,the minimum of shortwave radiation coincides with the maximum of wind speed and latent heat flux.This kind of MJO structure could make the maximum amplitude of net heat flux and the most significant variation of sea surface temperature(hereafter SST)in intraseasonal timescales.It is suggested that the air-sea interaction would play an important role in the MJO progress.It is necessary to confirm whether the intraseasonal variations of SST and mixed layer depth(hereafter MLD)are induced by MJO surface forcing.A simple one-dimensional mixed layer model(PWP)is used here to examine the unification of oceanic variability and atmospheric forcing.The phase relations and amplitudes of forcing fluxes inputted into the PWP model are referred to the above research.The intraseasonal variations of SST and MLD modeled by PWP are consistent with the observational results showed in the first part.This also suggests that the PWP model is appropriate enough to the study of MJO.An interannual variability of SST intraseasonal oscillation is observed especially in southwest Indian Ocean where the MLD and thermalcline are very shallow.Data analysis based on SST from Advanced Very High Resolution Radiometer(AVHRR), thermalcline from NCEP Global Ocean Data Assimilation System(GODAS)and air-sea heat fluxes from OAFlux,reveals that surface heat fluxes and oceanic subsurface processes play important roles in the interannual variability of SST intraseasonal oscillation.The SST intraseasonal oscillation will intensify as the intraseasonal amplitude of surface heat flux improved,and the same variation appears when the thermalcline rises.The remarkable signal that subsurface process influences the SST intraseasonal oscillation is found in the area where the thermalcline has the most obvious interannual variability.PWP mixed layer model is used again to check the regulative mechanism that we proposed above about the interannual variability of SST intraseasonal oscillation.And some simply designed numerical experiments give us a validation of the regulative mechanism.更多还原