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  1. Article ; Online: The vertical structure of annual wave energy flux in the tropical Indian Ocean

    Zimeng Li / Hidenori Aiki / Motoki Nagura / Tomomichi Ogata

    Progress in Earth and Planetary Science, Vol 8, Iss 1, Pp 1-

    2021  Volume 19

    Abstract: Abstract A recently developed energy flux diagnosis scheme, which incorporates a smooth connection between the tropical and subtropical zones, is used in the present study to investigate vertically propagating waves in the tropical Indian Ocean (IO) ... ...

    Abstract Abstract A recently developed energy flux diagnosis scheme, which incorporates a smooth connection between the tropical and subtropical zones, is used in the present study to investigate vertically propagating waves in the tropical Indian Ocean (IO) based on the result of a linear, continuously stratified ocean model driven by climatological wind forcing. This extended diagnosis reveals deep-reaching eastward energy fluxes at the equator which develop four times per year and are associated with equatorial Kelvin waves (KWs) generated by semiannual winds. The authors find that the downward transfer of wave energy is particularly deep in the southern Bay of Bengal (SBoB). This downward flux is attributed to off-equatorial Rossby waves and appears four times per year, maximizing its amplitude during November–December. Southwesterly winds in the Arabian Sea intensify eastward energy flux of KWs at mid-depth, which maximizes in amplitude in August. This is contrastive to KW energy flux at the surface which peaks in May. These mid-depth equatorial KW packets subsequently arrive at the eastern boundary of the IO and are diffracted poleward to produce downward energy flux in November and December detected in the SBoB.
    Keywords Indian Ocean ; Kelvin wave ; Rossby wave ; Seasonal variation ; Vertical structure ; Wave energy ; Geography. Anthropology. Recreation ; G ; Geology ; QE1-996.5
    Subject code 551
    Language English
    Publishing date 2021-07-01T00:00:00Z
    Publisher SpringerOpen
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Editorial

    Tomomichi Ogata / Takanori Horii / Hidenori Aiki / Yu-Lin K. Chang / Iskhaq Iskandar / Yukio Masumoto

    Frontiers in Climate, Vol

    Multi-scale air-sea variability and its application in Indo-Pacific regions

    2023  Volume 5

    Keywords El Niño-Southern Oscillation ; Indian Ocean Dipole (IOD) ; Indo-Pacific region ; tropical pacific and Indian Ocean ; tropical cyclone (TC) ; satellite observation ; Environmental sciences ; GE1-350
    Language English
    Publishing date 2023-07-01T00:00:00Z
    Publisher Frontiers Media S.A.
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Sporadic Low Salinity Signals in the Oceanic Mixed Layer Observed by the Kuroshio Extension Observatory Buoy

    Kohei Kameyama / Yuki Kanno / Shun Ohishi / Hiroyuki Tomita / Yoshiki Fukutomi / Hidenori Aiki

    Frontiers in Climate, Vol

    2022  Volume 4

    Abstract: The hourly measurements of air-sea interaction parameters made at the Kuroshio Extension Observatory (KEO) buoy since 2004 have produced an extensive dataset that can be used to understand the dynamics of the oceanic mixed-layer under extreme weather ... ...

    Abstract The hourly measurements of air-sea interaction parameters made at the Kuroshio Extension Observatory (KEO) buoy since 2004 have produced an extensive dataset that can be used to understand the dynamics of the oceanic mixed-layer under extreme weather conditions. Our analysis of the KEO-buoy measurements reveals the presence of sporadic low-salinity signals (SLSSs) with duration of 1–2 days in the mixed-layer when, for example, tropical cyclones (TCs) approach. Here SLSS events are identified within the buoy data by using a flag which is set to unity when the value of normalized salinity falls below −1 (minus one). Application of this definition to the hourly time series of salinity measured at 10 m depth by the KEO buoy has allowed us to identify 244 SLSS events over the 11-year analysis period. Both winter (January-March) and spring (April-June) seasons show a peak in the composite time series of wind velocity subdiurnal variation (WVDV) near the start time of SLSS events. SLSS events can be terminated by the entrainment of saltier subsurface water parcels to the mixed-layer in response to storms. The discovery of the WVDV peaks following SLSS commencement is the reason the present study has adopted a time scale of 1-day wind velocity analysis. This temporal resolution has enabled us to identify a TC-related delay in the development of the WVDV peaks, which may represent a fundamental characteristic of the influence of TCs on these events.
    Keywords precipitation ; composite time series ; surface skin layer ; tropical cyclones ; wind velocity subdiurnal variation ; Environmental sciences ; GE1-350
    Subject code 551
    Language English
    Publishing date 2022-03-01T00:00:00Z
    Publisher Frontiers Media S.A.
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Towards a seamlessly diagnosable expression for the energy flux associated with both equatorial and mid-latitude waves

    Hidenori Aiki / Richard J. Greatbatch / Martin Claus

    Progress in Earth and Planetary Science, Vol 4, Iss 1, Pp 1-

    2017  Volume 18

    Abstract: Abstract For mid-latitude Rossby waves (RWs) in the atmosphere, the expression for the energy flux for use in a model diagnosis, and without relying on a Fourier analysis or a ray theory, has previously been derived using quasi-geostrophic equations and ... ...

    Abstract Abstract For mid-latitude Rossby waves (RWs) in the atmosphere, the expression for the energy flux for use in a model diagnosis, and without relying on a Fourier analysis or a ray theory, has previously been derived using quasi-geostrophic equations and is singular at the equator. By investigating the analytical solution of both equatorial and mid-latitude waves, the authors derive an exact universal expression for the energy flux which is able to indicate the direction of the group velocity at all latitudes for linear shallow water waves. This is achieved by introducing a streamfunction as given by the inversion equation of Ertel’s potential vorticity, a novel aspect for considering the energy flux. For ease of diagnosis from a model, an approximate version of the universal expression is explored and illustrated for a forced/dissipative equatorial basin mode simulated by a single-layer oceanic model that includes both mid-latitude RWs and equatorial waves. Equatorial Kelvin Waves (KWs) propagate eastward along the equator, are partially redirected poleward as coastal KWs at the eastern boundary of the basin, and then shed mid-latitude RWs that propagate westward into the basin interior. The connection of the equatorial and coastal waveguides has been successfully illustrated by the approximate expression of the group-velocity-based energy flux of the present study. This will allow for tropical-extratropical interactions in oceanic and atmospheric model outputs to be diagnosed in terms of an energy cycle in a future study.
    Keywords Group velocity ; Model diagnosis ; Equatorial Rossby waves ; Equatorial mixed Rossby-gravity waves ; Equatorial inertia-gravity waves ; Equatorial Kelvin waves ; Geography. Anthropology. Recreation ; G ; Geology ; QE1-996.5
    Subject code 551
    Language English
    Publishing date 2017-03-01T00:00:00Z
    Publisher SpringerOpen
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

    More links

    Kategorien

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

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