Indo-Pacific Sea Surface Temperature Modes and their Impacts on East Asian Climate in Climate Model Environment
印太海温狀態與其對東亞氣候在氣候模式下的影響
Student thesis: Doctoral Thesis
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Award date | 5 Apr 2017 |
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Permanent Link | https://scholars.cityu.edu.hk/en/theses/theses(b3e5aba7-df0f-483a-a27d-15edb7930877).html |
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Other link(s) | Links |
Abstract
This study investigates the predictability of the two flavors of El Niño Southern Oscillation (ENSO) and their impacts on the East Asian (EA) Climate during the decaying phase (boreal spring and summer) using the Asia-Pacific Climate Center (APCC) Coupled Global Circulation Models (CGCMs).
For the predictability of ENSO, it is found that the models generally predict the persistence and spatial pattern of the canonical ENSO better than ENSO Modoki. The models always decay ENSO quicker than the observations, and the decay is more rapid for ENSO Modoki. Also, the projection coefficient and the degree of mixings method are carried out to access the ability of the models to differentiate the two ENSO flavors. The results show that the models with low degree of mixings tend to give good differentiation between the two ENSO flavors.
For the impacts of ENSO on the East Asian climate, it is found that, for the canonical ENSO, the location of the low level anti-cyclone plays an important role of the anomalous rainfall over the East Asia. The models generally give good predictions to the East Asian rainfall during the decaying boreal spring. It is also found that both predictions of canonical ENSO SST and the mean circulation over the East Asia affect the predictions of the El Niño precipitation over EA during the decaying summer of El Niño. However, for the decaying summer of ENSO Modoki, the predictions of ENSO Modoki SST seem not important, while the predictions of the mean circulation over EA are still crucial to the predictions of the Modoki rainfall over the EA.
For the Indian Ocean Empirical Orthogonal Function (EOF) analysis, it is found that the Indian Ocean Basin Mode (IOBM) has great lag relationship to the canonical ENSO, while the new discovered EOF4 of the Indian Ocean SSTA has some degree of relationship to the ENSO Modoki. The Subtropical Indian Ocean Dipole (SIOD) seems not to have too much relationship with the two flavors of ENSO.
For the predictability of ENSO, it is found that the models generally predict the persistence and spatial pattern of the canonical ENSO better than ENSO Modoki. The models always decay ENSO quicker than the observations, and the decay is more rapid for ENSO Modoki. Also, the projection coefficient and the degree of mixings method are carried out to access the ability of the models to differentiate the two ENSO flavors. The results show that the models with low degree of mixings tend to give good differentiation between the two ENSO flavors.
For the impacts of ENSO on the East Asian climate, it is found that, for the canonical ENSO, the location of the low level anti-cyclone plays an important role of the anomalous rainfall over the East Asia. The models generally give good predictions to the East Asian rainfall during the decaying boreal spring. It is also found that both predictions of canonical ENSO SST and the mean circulation over the East Asia affect the predictions of the El Niño precipitation over EA during the decaying summer of El Niño. However, for the decaying summer of ENSO Modoki, the predictions of ENSO Modoki SST seem not important, while the predictions of the mean circulation over EA are still crucial to the predictions of the Modoki rainfall over the EA.
For the Indian Ocean Empirical Orthogonal Function (EOF) analysis, it is found that the Indian Ocean Basin Mode (IOBM) has great lag relationship to the canonical ENSO, while the new discovered EOF4 of the Indian Ocean SSTA has some degree of relationship to the ENSO Modoki. The Subtropical Indian Ocean Dipole (SIOD) seems not to have too much relationship with the two flavors of ENSO.