The dynamics of error growth and predictability in a coupled model of ENSO
The dynamics of error growth and predictability in a coupled model of ENSO
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DOI：
10.1002/qj.49712253409
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发表时间：
1996-07
影响因子：
8.9
通讯作者：
A. Moore;R. Kleeman
中科院分区：
文献类型：
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作者：
A. Moore;R. Kleeman
使用新的和新兴的思想奇异向量（“最佳扰动”）的增长动力系统中，误差增长和可预测性的厄尔尼诺南方涛动（ENSO）的中间耦合模式的动力学进行了研究。一种机制，确定与大气中的渗透对流异常的误差增长。通过这种机制的误差增长的条件是最有利的中太平洋海表温度（SST）是相对温暖的，在SST的变化是适度敏感的主要海洋温跃层的垂直运动。利用切线-线性耦合模型及其伴随模型计算了耦合系统的奇异向量。奇异值谱被发现占主导地位的一个奇异向量在一年中的所有时间。耦合模型中的误差增长的潜力，测量的优势奇异向量的能量的增长，被发现随季节变化，在北方春季最大。这些季节变化与SST的季节循环有关。在北方春季和初夏，中太平洋的SST处于最大值，此时的条件最有利于误差的增长。春季也是ENSO的“可预测性障碍”的时间。误差增长的可能性也受到厄尔尼诺/南方涛动周期本身的影响。结果表明，误差增长将加强在厄尔尼诺和拉尼娜爆发期间抑制，这表明厄尔尼诺可能比拉尼娜更难预测。
Using new and emerging ideas about the growth of singular vectors (‘optimal perturbations’) in dynamical systems, the dynamics of error growth and predictability in an intermediate coupled model of the El Nino Southern Oscillation (ENSO) is investigated. A mechanism is identified for error growth associated with penetrative-convection anomalies in the atmosphere. Conditions for error growth via this mechanism are most favourable in the central Pacific where sea surface temperatures (SSTs) are relatively warm, and where changes in SST are moderately sensitive to vertical movements of the main oceanic thermocline. The singular vectors of the coupled system were computed using the tangent-linear coupled model and its adjoint. The singular-value spectrum was found to be dominated by one singular vector at all times of the year. The potential for error growth in the coupled model, measured in terms of the growth of energy of the dominant singular vector, is found to vary seasonally, being greatest during the boreal spring. These seasonal variations are associated with the seasonal cycle in SST. During boreal spring and early summer, the SST in the central Pacific is at its maximum, at which time conditions are most favourable for error growth. Springtime is also the time of the ‘predictability barrier’ for ENSO. The potential for error growth is also influenced by the ENSO cycle itself. The results suggest that error growth will be enhanced during the onset of El Nino and suppressed during the onset of La Nina, which indicates that El Nino may be less predictable than La Nina.