揭示地球物理系统多尺度耦合的小波相关性
Wavelet correlations to reveal multiscale coupling in geophysical systems
摘要：
气候与环境之间的相互作用非常复杂。由于这种复杂性，基于过程的模型往往是首选估计净规模和方向性的相互作用在地球系统。然而，这些模型是基于我们对自然的理解的简化，因此是不完美的。相反，由于空间传感技术和数据同化技术的进步，越来越多地可以获得大规模的气候和环境变量观测数据。虽然不确定，这些数据使可能性开始解开复杂的多变量，多尺度的关系，如果应用适当的统计方法。在这里，我们调查的小波互相关方法作为一种工具，用于识别多尺度的相互作用，反馈和政权转移的地球物理系统的潜力。小波互相关的能力，以解决耦合系统的快速和缓慢的组成部分进行测试的合成数据的已知方向性，然后应用到观测研究的最关键的陆地和大气之间的相互作用：土壤水分和近地面空气温度之间的耦合。结果表明，我们的方法不仅能够捕捉土壤水-温度耦合的动态在很宽的时间尺度（从几天到几个月）和气候制度（从湿到干），但也一致地确定耦合的大小和方向。因此，小波互相关作为一个有前途的工具，多尺度相互作用的研究，被扩展到地球系统的因果关系的分析的潜力。
英文摘要：
The interactions between climate and the environment are highly complex. Due to this complexity, process-based models are often preferred to estimate the net magnitude and directionality of interactions in the Earth System. However, these models are based on simplifications of our understanding of nature, thus are unavoidably imperfect. Conversely, observation-based data of climatic and environmental variables are becoming increasingly accessible over large scales due to the progress of space-borne sensing technologies and data-assimilation techniques. Albeit uncertain, these data enable the possibility to start unraveling complex multivariable, multiscale relationships if the appropriate statistical methods are applied. Here, we investigate the potential of the wavelet cross-correlation method as a tool for identifying multiscale interactions, feedback and regime shifts in geophysical systems. The ability of wavelet cross-correlation to resolve the fast and slow components of coupled systems is tested on synthetic data of known directionality, and then applied to observations to study one of the most critical interactions between land and atmosphere: the coupling between soil moisture and near-ground air temperature. Results show that our method is not only able to capture the dynamics of the soil moisture-temperature coupling over a wide range of temporal scales (from days to several months) and climatic regimes (from wet to dry), but also to consistently identify the magnitude and directionality of the coupling. Consequently, wavelet cross-correlations are presented as a promising tool for the study of multiscale interactions, with the potential of being extended to the analysis of causal relationships in the Earth system.
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