Analysis of the Mediterranean Precipitation Associated with the North Atlantic Oscillation (NAO) Index via Hilbert-Huang Transformation

• Main Author: Hasan Tatli
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Empirical mode decomposition; Hilbert-Huang Intrinsic Mode Functions; Mediterranean; precipitation; NAO index; North Atlantic; North Atlantic oscillation
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.325.8010; http://balwois.com/balwois/administration/full_paper/ffp-791.pdf

The state of the atmosphere is governed by the classical laws of fluid motion and exhibits a great deal of correlations in various spatial and temporal scales. The correlations are crucial to understand short and long-term variability in climate. The most significant correlations are recognized as teleconnection patterns. One of those connections is the North Atlantic Oscillation (NAO) which is associated with anomalous weather patterns in eastern United States, Western Europe and Mediterranean. Although, there is a consensus on physically relationship between the NAO index and precipitation series, the results of statistical analysis drawbacks such strong correlation. The gap between the physical and statistically approach might be filled by integrating through the time of the NAO index and precipitation. After transforming both of the NAO index and precipitation series, each of them behaves as the output of a low-order dynamical system. In this study, Empirical Mode Decomposition (EMD) method of Huang is employed to cut up the total NAO index data into different narrow-band frequency components, and then studying each of the components with a resolution harmonized to its scale of which are called Intrinsic Mode Functions (IMFs) of the underlying physical dynamics having advantages over traditional Fourier analysis in analyzing physical situations, where the signal contains discontinuities and sharp spikes in a domain of non-linear and non-stationary space case. The EMD method is performed to extract oscillatory modes in the total NAO index in order to reduce the relationship between the each of the IMFs and large-scale precipitation comparing with the embedding method of non-linear dynamical systems approach. The results show that the total NAO index exhibits substantial organized and correlated structures with precipitation variability over the Mediterranean.