Analysis of the forcings of the Pacific Decadal Oscillation in CCSM4
Date
2014
Authors
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Publisher
University of Delaware
Abstract
The Pacific Decadal Oscillation (PDO), a variation of sea surface temperatures in the North Pacific Ocean, is analyzed using modeled output from the Community Climate System Model (CCSM) 4.0. The proposed forcings which cause this variation are fluctuations in the El Nino Southern Oscillation cycle, the Hadley cell circulation, the sea level pressure field and the western boundary current in the North Pacific, compromising a cycle outlined by DiLorenzo et al, 2010. This study uses modeled output as opposed to observational data due to temporal and spatial coverage available to replicate the components of the cycle. The spatial patterns are represented with the first empirical functions of each field and the temporal patterns are represented by the time series of annual averages centered on the winter season. The correlations between the other components and the PDO index indicate that they vary on the same time scale. Lag correlation is used to understand how the proposed components change in relation to each other temporally to map out the possible cycle in the model output. Results showed that the eastern Pacific fields responded faster than the western Pacific field, with a lag of 1 year compared to a lag of 5 years. Many of the lags found between components were consistent with past studies, while other varied slightly.