Climatic forcing on hydrography of a Mediterranean bay (Alfacs Bay) |
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| Authors: | Jordi Sol Antonio Turiel Marta Estrada Clara Llebot Dolors Blasco Jordi Camp Maximino Delgado Margarita Fernndez-Tejedor Jorge Diogne |
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| Institution: | aIMEDEA (CSIC-UIB), Miquel Marques 21, 07910 Esporles, Mallorca, Spain;bInstitut de Ciències del Mar (CSIC), 08003 Barcelona, Catalunya, Spain;cCentre d’Aquicultura (IRTA), Ctra. Poble Nou, s/n Km 5,5, 43540 Sant Carles de la Rapita Catalunya, Spain |
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| Abstract: | Time series of meteorological and hydrographic variables were analyzed using Huang's Empirical Mode Decomposition (EMD) to ascertain the relationships among climatic forcings and the hydrographic behavior in an estuarine bay. The EMD method allowed us to separate the different characteristic oscillation patterns (or modes) of a 14 year-long time series of weekly hydrographic (water temperature and salinity) and meteorological (air temperature, pressure, wind and precipitation) data from Alfacs Bay (Ebre delta, NW Mediterranean). In order to explore the relations between couples of oscillation modes from different series, we developed a correlation index based on the phase differences between these modes. Common characteristic modes in the studied series are a seasonal pattern and an inter-annual oscillation. The comparison between series of meteorological and hydrographic variables shows significant correlations of two modes (of 1 year and 2–3 year periods, respectively) of water temperature with the corresponding two modes of air temperature and air pressure. There were also significant positive correlations between wind speed and water temperature. The use of EMD allowed to discover a strong connection between stratification and the use of irrigation channels in the bay; in addition, with the help of this method we can propose a common meteorological forcing mechanism for the observed patterns of variability. Those findings would have been impossible to guess by use of classical Fourier methods, and gives a demonstration of the power of EMD in climatic series analysis. |
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| Keywords: | Signal processing Empirical mode decomposition Intrinsic mode functions Alfacs Bay Mediterranean Sea Local phase |
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