Study on the variability and irregularity of the ENSO-like behavior of the Pacific with coupled general circulation models

• Main Authors: 行本, 誠史, 34803, Yukimoto, Seiji
• Language: Japanese
• Published: 2003
• Subjects: aleutian low
• Online Access: https://tsukuba.repo.nii.ac.jp/record/8367/files/B1968.pdf; https://tsukuba.repo.nii.ac.jp/record/8367/files/1.pdf

筑波大学 University of Tsukuba 博士（理学） Doctor of Philosophy in Science This dissertation describes interannual and interdecadal variabilities in the Pacific, which are simulated with two versions of the global coupled ocean-atmosphere general circulation model (CGCM) developed at Meteorological Research Institute, along with validations for the models. The first version of the CGCM (MRI-CGCM1) simulates natural climate variability in the Pacific Ocean, which reveals features in various aspects similar to the observation. The simulated interannual variability in the tropical Pacific exhibits several typical characteristics shared with the observed El Nino and Southern Oscillation (ENSO). For the simulated ENSO, a basin-scale feature of the principal sea surface temperature (SST) variation shows negative correlation between the central North Pacific and the tropical Pacific, as in the observed ENSO. Associated variation of the model atmosphere indicates an intensification of the Aleutian Low and a PNA-like teleconnection pattern as a response to the tropical warm SST anomaly. The ENSO time scale variability in the midlatitude ocean consists of the westward propagation of the subsurface temperature signal and the temperature variation within the shallow mixed layer forced by the anomalous atmospheric heat fluxes. Spatial and temporal structures of variability in the Pacific Ocean are investigatedusing a set of two experiments with the MRI-CGCM1. The standard experiment with dynamical ocean shows basin-wide spatial pattern of the principal SST variability similar to the observed one. Both interdecadal and interannual temporal structures of the SST variability agree well between the observation and the model. On the other hand, a slab ocean coupled to the same atmospheric model fails simulating the observed temporal structure. It is suggested, therefore, that the timescale of the coupled variability is associated with dynamical processes in the ocean. A distinct interdecadal mode of the coupled atmosphere-upper ...