Stochastic climate models , Part I 1 Application to sea-surface temperature anomalies and thermocline variability
Stochastic climate models , Part I 1 Application to sea-surface temperature anomalies and thermocline variability
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2010
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本系列第一部分（Hasselmann，1976）中提出的随机气候模式的概念被应用于海洋上层低频变率的研究。结果表明，大尺度、长时间的海表温度（SST）异常可以自然地解释为海洋表层对短时间尺度大气强迫的响应。大气输入的白噪声谱产生红色响应谱，大部分方差集中在很长的周期内。如果没有稳定的负反馈，海洋响应将是非平稳的，总的SST方差随时间无限增长。在负反馈下，响应是渐近平稳的。这些影响是通过一个非常简单的海洋-大气模式的数值实验来说明的。该模式再现了中纬度地区观测到的SST异常的主要特征和数量级。独立的随机强迫模式提供了直接比较观测到的感热和潜热通量谱与SST异常谱，也由大气表面气压和SST异常型的互相关函数的结构。数值模式进一步用于模拟风应力旋度驱动的Ekman泵作用下的近地表温跃层异常。结果表明，短时间尺度的大气强迫应被视为一个可能的候选人的起源大尺度，低周期的变化，在季节性温跃层。
The concept of stochastic climate models developed in Part I of this series (Hasselmann, 1976) is applied to the investigation of the low frequency variability of the upper ocean. It is shown that large-scale, long-time sea surface temperature (SST) anomalies may be explained naturally as the response of the oceanic surface layers to short-time-scale atmospheric forcing. The whitenoise spectrum of the atmospheric input produces a red response spectrum, with most of the variance concentrated in very long periods. Without stabilizing negative feedback, the oceanic response would be nonstationary, the total SST variance growing indefinitely with time. With negative feedback, the response is asymptotically stationary. These effects are illustrated through numerical experiments with a very simple ocean-atmosphere model. The model reproduces the principal features and orders of magnitude of the observed SST anomalies in mid-latitudes. Independent support of the stochastic forcing model is provided by direct comparisons of observed sensible and latent heat flux spectra with SST anomaly spectra, and also by the structure of the cross correlation functions of atmospheric surface pressure and SST anomaly patterns. The numerical model is further used to simulate anomalies in the near-surface thermocline through Ekman pumping driven by the curl of the wind stress. The results suggest that short-time-scale atmospheric forcing should be regarded as a possible candidate for the origin of large-scale, low-period variability in the seasonal thermocline.