Parameterizing the nonlinear feedback on ENSO from tropical instability waves (TIWs) by nonlinear eddy thermal diffusivity
Parameterizing the nonlinear feedback on ENSO from tropical instability waves (TIWs) by nonlinear eddy thermal diffusivity
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DOI：
10.1007/s00382-023-06744-4
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发表时间：
2023-03-24
期刊：
影响因子：
4.6
通讯作者：
Kug，Jong-Seong
中科院分区：
文献类型：
--
作者：
Xue，Aoyun;Jin，Fei-Fei;Kug，Jong-Seong
作为赤道东太平洋中尺度变率的主要形式，热带不稳定波（TIWs）以复杂的方式与厄尔尼诺Niño和南方涛动（ENSO）相互作用。TIWs的活动受到ENSO状态的调节，并通过非线性动态加热（NDH）对ENSO提供重要反馈，作为El Niño和La Niña相之间不对称的来源。研究表明，TIWs引起的热通量和NDH的年际变化可以用平均经向温度梯度近似表示，因为TIWs倾向于沿海表温度锋的温度异常梯度向下输送热量。TIWs诱导的NDH可以量化为非线性热涡扩散率对ENSO的不对称负反馈，这取决于背景TIWs模式和与ENSO相关的线性和非线性过程。所提出的参数化方案可以很好地捕捉到ENSO对TIWs活动的直接调制、ENSO与冷舌年循环非线性相互作用的组合效应以及相关的ENSO非线性。该参数化方案使用四个具有不同水平分辨率的海洋再分析数据集进行了有效测试，这些数据集显示了TIWs活动的对比模式。该方案可用于评估机制ENSO模型中tiws诱导的ENSO反馈，从而更好地理解ENSO复杂性的动力学。
As the dominant form of mesoscale variability in the equatorial eastern Pacific, Tropical Instability Waves (TIWs) are known to interact with the El Niño and Southern Oscillation (ENSO) in complex ways. TIWs activity is modulated by the ENSO state and also provide significant feedback on ENSO via nonlinear dynamic heating (NDH), acting as a source of asymmetry between the El Niño and La Niña phases. In this work, we show that the interannual variability of TIWs-induced heat flux and NDH can be approximately expressed in terms of the mean meridional temperature gradient as TIWs tend to transport heat downgradient of the temperature anomalies along the Sea Surface Temperature (SST) front. The TIWs-induced NDH can be quantified as an asymmetric negative feedback on ENSO by a nonlinear thermal eddy diffusivity which depends on the background TIWs pattern and the ENSO-related linear and nonlinear processes. This proposed parameterization scheme can capture well the direct ENSO modulation on TIWs activity, the combination effect arising from the nonlinear interaction between ENSO and the cold tongue annual cycle, and associated ENSO nonlinearity. This parameterization scheme is effectively tested using four ocean reanalysis datasets with different horizontal resolutions that exhibit contrasted patterns of TIWs activity. This scheme may be useful for assessing the TIWs-induced feedback on ENSO in mechanistic ENSO models to better understand the dynamics of ENSO complexity.