New Methods for Estimating Ocean Eddy Heat Transport Using Satellite Altimetry
New Methods for Estimating Ocean Eddy Heat Transport Using Satellite Altimetry
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DOI：
10.1175/mwr-d-11-00145.1
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发表时间：
2012-05-01
影响因子：
3.2
通讯作者：
Smith, K. Shafer
中科院分区：
文献类型：
--
作者：
Keating, Shane R.;Majda, Andrew J.;Smith, K. Shafer
监测海洋涡流热量输送的努力受到现有观测稀少以及热量输送是一个对未分辨尺度特别敏感的二次型符号不确定量这一事实的强烈限制。在本文中，一套用于估计涡热输送的随机滤波策略在一系列观测情景下，在理想的两层中尺度海洋湍流模拟中进行了检验。这些滤波策略的一个新特点是使用计算成本低的随机模型来预测潜在的非线性动态。随机模型的参数可以通过对气候能谱和相关时间的回归拟合来估计，或者通过自适应地从观测值中自适应地学习这些参数来估计。作者表明，通过提取已被混叠到低波数带的高波数信息，可以得到名义分辨率增加2倍或更多的“随机超分辨”速度场。上层流函数的观测值被投影到垂直结构的经验正交函数基础上，以产生上层和下层流函数的过滤估计，从而产生净热量传输。与基于最优内插的标准估计相比，所得到的时间平均极地涡热输送明显更接近真实值。相比之下，由于时间分辨率较差，热传输的时间变异性被低估了。讨论了使用当前和下一代高度计估计极地涡热输送的意义。
Attempts to monitor ocean eddy heat transport are strongly limited by the sparseness of available observations and the fact that heat transport is a quadratic, sign-indefinite quantity that is particularly sensitive to unresolved scales. In this article, a suite of stochastic filtering strategies for estimating eddy heat transport are tested in idealized two-layer simulations of mesoscale oceanic turbulence at high and low latitudes under a range of observation scenarios. A novel feature of these filtering strategies is the use of computationally inexpensive stochastic models to forecast the underlying nonlinear dynamics. The stochastic model parameters can be estimated by regression fitting to climatological energy spectra and correlation times or by adaptively learning these parameters "on-the-fly" from the observations themselves.The authors show that, by extracting high-wavenumber information that has been aliased into the low wavenumber band, "stochastically super-resolved" velocity fields with a nominal resolution increase of a factor of 2 or more can be derived. Observations of the upper-layer streamfunction are projected onto an empirical orthogonal function basis for the vertical structure to produce filtered estimates for both upper- and lower-layer streamfunctions and hence net heat transport. The resulting time-mean poleward eddy heat transport is significantly closer to the true value when compared with standard estimates based upon optimal interpolation. By contrast, the temporal variability of the heat transport is underestimated because of poor temporal resolution. Implications for estimating poleward eddy heat transport using current and next-generation altimeters are discussed.