学位論文 Origin of Intraseasonal Variability in the Eastern Equatorial Indian Ocean : Intrinsic Variability, and Local and Remote Wind-Stress Forcings

李, チョロン

2017-09-25
内容記述
Eastern equatorial Indian Ocean ( E EIO) experience s large intraseasonal variability (ISV) , which arises from intrinsic variability and also is induced by local and remote atmospheric forcings. We investigate the relative contributions of intrinsic variability and local and remote forcings to ISV in E E IO by conducting a set of numerical model experiments using Regional Ocean Model System over the Indian Ocean with grid interval of 0.25° in longitudes and latitudes. In the control run , the model is forced year - to - year varying forcings for 20 years (1996 – 2015) . We account the first 10 years as the necessary period to spin up. The control run can reproduce realistic ISV in EEIO. To distinguish ISV originating from intrinsic variability and that caused by atmospheric forcings, we examine three experiments with di fferent perturbation at the beginning of 10 - year integration (2006 - 2015). The ensemble - mean of these experiments represents forced responses, while differences among the experiments indicate the intrinsic variability. In the central to eastern equatorial Indian Ocean, forced oceanic ISV is much larger than intrinsic ISV in the whole 500 m depth. For ISV of sea surface temperature , atmospheric forcings play a larger role than intrinsic variability in the most region of the Indian Ocean. Atmospheric f orced I SV distinctly penetrates to the subsurface in EEIO. To understand a relative role of atmospheric forcings, especially that of wind - stress, f our regional forcing experiments are conducted . In the first two experiments, wind - stress ISV is retained over western (west of 80°E) or eastern (east of 80°E) region , while in the other two experiments the latter forcing region is further subdivided into middle eastern (80° – 100°E) and far eastern (east of 100°E) regions . At the surface, local forcing, especially i n the middle eastern Indian Ocean, dominates ISV in EEIO. In the subsurface, remote forcing also plays an important role in ISV. Below the thermocline, the influence of wind forcing from the west of 80°E cannot be neglected on ISV, even work constructively with that from the east of 80°E . The contribution of wind forcing east of 100 °E is small but cannot be ignored near the Java coast.
56p
Hokkaido University(北海道大学). 博士(理学)
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https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/67405/1/Chorong_Lee.pdf

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