Takaya Uchida

Takaya Uchida
Florida State University | FSU · Centre for Ocean-Atmospheric Prediction Studies (COAPS)

Doctor of Philosophy
Just a nerd in it for the fun.

About

28
Publications
3,325
Reads
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148
Citations
Introduction
I'm an early-career Assistant Research Scientist at the Center for Ocean-Atmospheric Prediction Studies (COAPS). My research interests span from old-school geophysical fluid dynamics and (sub)mesoscale turbulence to eddy momentum/tracer fluxes and how they affect the physical-biogeochemical coupling. I use numerical models and autonomous/remote-sensed observations as the tools of investigation.
Additional affiliations
October 2019 - September 2022
French National Centre for Scientific Research
Position
  • PostDoc Position
Description
  • Physical Oceanographer as part of the MultiscalE Ocean Modelling (MEOM) group.
Education
September 2014 - October 2019
Columbia University
Field of study
  • Physical Oceanography

Publications

Publications (28)
Article
Full-text available
The primary productivity of the Southern Ocean ecosystem is limited by iron availability. Away from benthic and aeolian sources, iron reaches phytoplankton primarily when iron-rich subsurface waters enter the euphotic zone. Here, eddy-resolving physical/biogeochemical simulations of a seasonally-forced, open-Southern-Ocean ecosystem reveal that mes...
Article
Full-text available
The thickness-weighted average (TWA) framework, which treats the residual-mean flow as the prognostic variable, provides a clear theoretical formulation of the eddy feedback onto the residual-mean flow. The averaging operator involved in the TWA framework, although in theory being an ensemble mean, in practice has often been approximated by a tempo...
Article
Full-text available
With the increase in computational power, ocean models with kilometer-scale resolution have emerged over the last decade. These models have been used for quantifying the energetic exchanges between spatial scales, informing the design of eddy parametrizations, and preparing observing networks. The increase in resolution, however, has drastically in...
Preprint
Full-text available
The anisotropic mesoscale eddy diffusivity tensor is diagnosed using passive tracers advected online in both an idealized 101-member mesoscale-resolving quasi-geostrophic (QG) double-gyre ensemble, and a realistic 24-member eddying ($1/12^\circ$) ensemble of the North Atlantic. We assert that the Reynold's decomposition along the ensemble dimension...
Article
Full-text available
A submesoscale-permitting global ocean simulation is used to study the upper ocean turbulence in high kinetic energy (KE) regions. Submesoscale processes peak in winter so that the geostrophic KE spectra tend to be relatively shallow in winter ($\sim k^{-2}$) with steeper spectra in summer ($\sim k^{-3}$). This transition in KE spectral scaling has...
Preprint
Full-text available
A wavelet-based method is introduced in an oceanographic context to estimate wavenumber spectrum and spectral flux of kinetic energy and enstrophy. We apply this to a numerical simulation of idealized, doubly-periodic quasi-geostrophic flows, i.e. the flow is constrained by the Coriolis force and vertical stratification. The double periodicity allo...
Article
Full-text available
The `eddying' ocean, recognized for several decades, has been the focus of much observational and theoretical research. We here describe a generalization for the analysis of eddy energy, based on the use of ensembles, that addresses two key related issues: the definition of an `eddy' and the general computation of energy spectra. An ensemble identi...
Article
Full-text available
Mesoscale eddies, although being on the scales of O (20–100km), have a dispro-portionate role in shaping the mean stratification, which varies on the scale of O (1000km). With the increase in computational power, we are now able to partially resolve the eddies in basin-scale and global ocean simulations, a model resolution often referred to as meso...
Preprint
Full-text available
With the increase in computational power, ocean models with kilometer-scale resolution have emerged over the last decade. These models have been used for quantifying the energetic exchanges between spatial scales, informing the design of eddy parametrizations and preparing observing networks. The increase in resolution, however, has drastically inc...
Preprint
Full-text available
Understanding how kinetic energy (KE) is exchanged across scales and eventually dissipated remains a key question in physical oceanography. Recent theoretical works suggests that both quasi-balanced submesoscale motions and internal gravity waves (IGWs) could play a role in fluxing KE towards dissipation. How these classes of motions actually provi...
Preprint
The 'eddying' ocean, recognized for several decades, has been the focus of much observational and theoretical research. We here describe a generalization for the analysis of eddy energy, based on the use of ensembles, that addresses two key related issues: the definition of an 'eddy' and the general computation of energy spectra. An ensemble identi...
Conference Paper
Full-text available
The oceanographic and atmospheric science community has had a long standing interest in the Eliassen-Palm (E-P) flux divergence, which encapsulates the net eddy feedback onto the mean flow. Nevertheless, a comprehensive understanding of it has remained illusive. This has partially been due to the fact that the E-P flux divergence and not the flux i...
Article
With the advent of submesoscale O(1 km) permitting basin-scale ocean simulations, the seasonality of mesoscale O(50 km) eddies with kinetic energies peaking in summer has been commonly attributed to submesoscale eddies feeding back onto the mesoscale via an inverse energy cascade under the constraint of stratification and Earth’s rotation. In contr...
Preprint
Full-text available
Mesoscale eddies, the weather system of the oceans, although being on the scales of O(20-100 km), have a disproportionate role in shaping the mean jets such as the separated Gulf Stream in the North Atlantic Ocean, which is on the scale of O(1000 km) in the along-jet direction. With the increase in computational power, we are now able to partially...
Preprint
Full-text available
With the advent of submesoscale $O(1~\text{km})$ permitting basin-scale ocean simulations, the seasonality of mesoscale $O(50~\text{km})$ eddies with kinetic energies peaking in summer has been commonly attributed to submesoscale eddies feeding back onto the mesoscale via an inverse energy cascade under the constraint of stratification and Earth's...
Article
Full-text available
The flow of energy in the wind-driven circulation is examined in a combined theoretical and numerical study. Based on a multiple-scales analysis, we find the mesoscale field in the ocean interior is strongly affected by, but does not feed back onto, the ventilated thermocline. In the western boundary region, the associated currents first appear as...
Preprint
The flow of energy in the wind-driven circulation is examined in a combined theoretical and numerical study. Based on a multiple-scales analysis, we find the mesoscale field in the ocean interior is strongly affected by, but does not feed back onto, the ventilated thermocline. In the western boundary region, the associated currents first appear as...
Preprint
A submesoscale-permitting global ocean model is used to study the upper ocean turbulence. Submesoscale processes peak in winter and, consequently, geostrophic kinetic energy (KE) spectra tend to be relatively shallow in winter (∼ k−2) with steeper spectra in summer (∼ k−3). This seasonal transition from steep to shallow power-law in the KE spectra...
Preprint
Full-text available
The thickness-weighted average (TWA) framework, which treats the residual-mean flow as the prognostic variable, provides a clear theoretical formulation of the eddy feedback onto the residual-mean flow. The averaging operator involved in the TWA framework, although in theory being an ensemble mean, in practice has often been approximated by a tempo...
Conference Paper
Many ocean and climate models output ocean variables (like velocity, temperature, oxygen concentration etc.) in depth space. Property transport in the ocean generally follows isopycnals, but isopycnals often move up and down in depth space. A small difference in the vertical location of isopycnals between experiments can cause a large apparent diff...
Article
Full-text available
Biological productivity in the Southern Ocean is limited by iron availability. Previous studies of iron supply have focused on mixed‐layer entrainment and diapycnal fluxes. However, the Southern Ocean is a region highly energetic mesoscale and submesoscale turbulence. Here we investigate the role of eddies in supplying iron to the euphotic zone, us...
Article
Full-text available
The spring bloom in the Southern Ocean is the rapid-growth phase of the seasonal cycle in phytoplankton. Many previous studies have characterized the spring bloom using chlorophyll estimates from satellite ocean color observations. Assumptions regarding the chlorophyll-to-carbon ratio within phytoplankton and vertical structure of biogeochemical va...
Thesis
Full-text available
Mesoscale turbulence is ubiquitous in the surface ocean and has significant impact on the large-scale ocean circulation and its interaction with the climate. Ocean currents are most energetic in the mesoscale range on the scales of 20-200 km and recent studies have shown that the surface kinetic energy associated with the mesoscale undergo a large...
Preprint
The primary productivity of the Southern Ocean ecosystem, and associated biological carbon pump, is limited by the availability of the micronutrient iron. Riverine sediments and atmospheric dust supply iron at the ocean margins, but in the vast open ocean, iron reaches phytoplankton primarily when iron-rich sub-surface waters enter the euphotic zon...
Preprint
In order to examine the roles of ocean dynamics in supplying iron, the limiting nutrient in the open Southern Ocean, to the surface where it can be effectively utilized for photosynthesis, we run a flat-bottom zonally re-entrant channel model configured to represent the Antarctic Circumpolar Current region and couple it to a full biogeochemical mod...
Preprint
The spring bloom in the Southern Ocean is the rapid-growth phase of the seasonal cycle in phytoplankton. Many previous studies have characterized the spring bloom using chlorophyll estimates from satellite ocean color observations. Assumptions regarding the chlorophyll-to-carbon ratio within phytoplankton and vertical structure of biogeochemical va...
Article
We examine the seasonal cycle of upper-ocean mesoscale turbulence in a high resolution CESM climate simulation. The ocean model component (POP) has 0.1° resolution, mesoscale resolving at low and middle latitudes. Seasonally and regionally resolved wavenumber power spectra are calculated for sea-surface eddy kinetic energy (EKE). Although the inter...
Thesis
Full-text available
Analysis of island-trapped waves has been made off the Izu-Islands, particularly around the Miyake Island and the Hachijo Island. The ITWs were observed in reanalysis data of current velocity, sea-surface elevation, temperature and salinity provided by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). From Fourier analysis and cro...

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Projects

Projects (2)
Project
With the increase in computational power, ocean models with kilometer-scale resolution have emerged over the last decade. These models have been used for quantifying the energetic exchanges between spatial scales, informing the design of eddy parametrizations and preparing observing networks. The increase in resolution, however, has drastically increased the size of model outputs, making it difficult to transfer and analyze the data. The realism of individual models in representing the energetics down to numerical dissipation has also come into question as we start to resolve more small-scale dynamics. We implement a cloud-based analysis framework proposed by the Pangeo Project that aims to tackle such data distribution and analysis challenges. We analyze the output of eight submesoscale-permitting realistic simulations, all on the cloud, in anticipation of the upcoming Surface Water and Ocean Topography (SWOT) altimeter mission. (https://github.com/pangeo-data/swot_adac_ogcms)
Project
To formulate a potential vorticity based mesoscale eddy closure scheme, which incorporates the eddy momentum fluxes in addition to bringing together the eddy buoyancy fluxes (GM) and isopycnic tracer stirring (Redi), with the foresight of improving mesoscale permitting general circulation models. We will harness ensemble simulations to achieve this goal.