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基于2005年至2009年、2011年和2013年各年九月份南海开放航次获取的南海东北部120°E断面的水文观测资料,运用了地转流诊断和模态分解两种方法,研究了该断面流场结构和体积输运的年际变化特征。2005年、2006年、2007年和2013年流场呈显著斜压特征,断面上、下层流速方向相反;而2008、2009年和2011流场垂向变化不明显,呈现准正压结构。断面体积输运沿深度分布呈现三种方式:一致向西(2005年、2007年和2011年),上西下东(2008年和2013年)和上东下西(2006年和2009年)。断面净体积输运亦有显著年际变化,在2005年出现西向最大–11.2Sv,在2013年出现东向最大9.1Sv,而在2009年仅为西向-1.2Sv。模态分解表明,准正压结构的年份,流场主要被正压模态控制,但第一斜压模态亦不可忽略;而斜压结构的年份,流场由正压模态和第一斜压模态共同主导。
Based on the hydrographic data of the 120 ° E section of the northeastern South China Sea obtained from the open sea voyage in the South China Sea from September 2005 to 2009, 2011 and 2013 in each of the three seasons, the geostationary fault diagnosis and the modal decomposition are used. INTERANNUAL VARIABILITY OF STRUCTURE AND VOLUME TRANSPORT OF FLOW IN CROSS SECTION. In 2005, 2006, 2007 and 2013, the flow field showed a significant baroclinic characteristic with opposite flow velocities in the upper and lower layers. In 2008, 2009 and 2011, the vertical variation of the flow field was not obvious, showing a quasi-positive pressure structure. The distribution of cross-section volumetric transport along the depth shows three ways: consistent west (2005, 2007 and 2011), the upper east-lower east (2008 and 2013) and the upper east and west (2006 and 2009). There was also a significant interannual variation of net volumetric transport in section, with a maximum of -11.2Sv in west direction in 2005, a maximum of 9.1Sv in east direction in 2013 and a -1.2Sv in west direction in 2009. The modal decomposition shows that in the quasi-positive pressure structure, the flow field is mainly controlled by the positive pressure mode, but the first pressure mode can not be neglected. In the year of the baroclinic structure, the flow field is controlled by the positive pressure mode and the first Baroclinic mode common dominance.