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Deepak Cherian

physical oceanographer
Research Associate (Post-doc), Oregon State University

Current Research

Mixing measurements in the Bay of Bengal

With Emily Shroyer (OSU), Jim Moum (OSU) & the OSU Ocean Mixing Group.

bob-chipods.png

Multiple year-long moored turbulent mixing measurements collected using fast temperature sensors (χ-pods) as part of the ASIRI/DYNAMO/EBoB/RAMA programmes paint a picture of mixing across the Bay of Bengal that spans multiple time scales: interannual to diurnal and shorter.

Interesting signals include interannual & intraseasonal variability, a daily cycle in turbulence, depressed turbulence in barrier layers, elevated mixing associated with the tropical cyclones and a quiet ocean below 50m.

(map shows past and proposed deployments - courtesy Emily Shroyer)

Inertial-gravity waves in the equatorial Pacific

With Tom Farrar (WHOI) & Ted Durland (OSU) | Code | More

farrar-durland-spectrum-deepak.png

Satellite observations give humanity an unprecedented detailed look at the surface ocean. The vertical structure of variability associated with surface signals is relatively less known, and the relevance of theoretical structures derived using strict assumptions is debated; viz., the so-called baroclinic vertical modes.

Motivated by the [zonal wavenumber]-frequency spectra of dynamic height calculated by Farrar & Durland (2012) — see image on right — my goal is to infer the vertical structure of 7-day period inertial-gravity waves in the equatorial Pacific (filter band marked by horizontal lines). I am using long term subsurface temperature measurements and inferred dynamic height from the TAO/TRITON project.

Shelf flows forced by mesoscale eddies

Advisor: Ken Brink (WHOI) | More

One chapter of my dissertation focused on the shelf flows forced by mesoscale eddies translating at the shelfbreak. A manuscript is in preparation.

shelf-flow-summary.png

Cross-shelfbreak exchange by mesoscale eddies

Advisor: Ken Brink (WHOI) | Read the paper! | Video | More

eddyshelf-3d.png

My dissertation looked at the interaction of deep-ocean mesoscale eddies with continental shelf-slope topography.

When visualized using passive tracer fields (red tracks eddy water and blue, shelf-slope water), the interaction clearly results in the formation of smaller-scale secondary vortices. We term these 'stacked' vortices to reflect their (unexpected) vertical structure wherein shelf-slope water is stacked over eddy water.

Observational evidence for these features remains elusive.

Publications

nearly done

  • Cherian D.A., Brink K.H. Shelf flows forced by deep-water anticyclonic eddies at the shelfbreak.
  • Cherian D.A., Farrar J.T., Durland T.S. The upper-ocean vertical structure of 7-day period inertial-gravity waves in the equatorial Pacific.

2016

  • Cherian D.A., Brink K.H. (2016) Offshore Transport of Shelf Water by Deep-Ocean Eddies. Journal of Physical Oceanography. 46 3599–3621. DOI PDF

2013

  • Haine T.W.N., Cherian D.A. (2013) Analogies of Ocean/Atmosphere Rotating Fluid Dynamics with Gyroscopes: Teaching Opportunities. Bull. Amer. Meteor. Soc.. 94:684. DOI PDF Supplement
  • Brink K.H., Cherian D.A. (2013) Instability of an idealized tidal mixing front: Symmetric instabilities and frictional effects. Journal of Marine Research. 71(6):26. DOI PDF

Thesis

  • Cherian D.A. (2016) When an eddy encounters shelf-slope topography. PDF

Teaching

While at MIT, I took the semester-long Teaching Certificate Program. I learned that it is generally more effective to have students work through a derivation primarily on their own in class with hints. Following that advice, I created worksheets that guide students through a derivation, guiding them toward important implications and reasoning for various steps. Here are the ones I have so far.

  1. Rossby adjustment
  2. Non-hydrostatic internal waves
  3. Sverdrup balance - for MIT's 12.808 - Observational Physical Oceanography

Any comments you might have on these are welcome. Please send me an email.

Latex source is also available on request.

Posts

Contact

Email:

Office Address: Burt 434, OSU, Corvallis SSR, OR

Acknowledgments

My work has been funded by the US National Science Foundation and the Office of Naval Research.

Styling gratefully borrowed from Ethan Schoonover, Nicolas P. Rougier and Matthew Butterick.

Icons from FontAwesome and Academicons.

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