Je suis singapourien d'origine chinoise. A Singapour, nous apprenons l'anglais et une de nos langues maternelles, c'est-à-dire le chinois pour moi. Le français n'est qu'une troisième langue pour moi. Je l'apprends depuis 1995 et j'ai eu l'occasion de le beaucoup pratiquer quand je vivais en France pendant trois mois en 2001. La photo ci-dessus a été prise pendant un séjour en Allemagne en 2002.
Hello everybody! It is a pleasure to meet you. I am an atmospheric scientist from Singapore. I read my PhD dissertation at Massachusetts Institute of Technology (MIT). After graduation, I worked as a visiting scientist at the Laboratoire de Météorologie Dynamique (LMD) in Paris, before returning to Singapore to serve in Temasek Laboratories @ National University of Singapore (TL@NUS). Currently, I am an Assistant Professor at the School of Physical and Mathematical Sciences, Nanyang Technological University (NTU). (Click here for my staff profile at NTU.)
Okay, now that you know a little of me, we can go on to the serious business of what this web page is all about. (:>)
MAS 181 Calculus for the Sciences I
Calculus forms a cornerstone to the physical sciences, from describing the motion of a simple pendulum to
unraveling the complex reactions of chemical compounds. It has to do with taking derivatives and making
integrals. Or stated more intuitively, it deals with finding the gradients of and the area underneath graphs.
Our approach to the subject is based on real-world examples. Abstraction from these physical examples
naturally brings out the fundamental mathematical concepts. At the same time, mathematical rigor will
be preserved as much as possible to highlight the important role of mathematics underlying the physical
sciences. The student learns to apply mathematical concepts learnt in lectures through tutorial problem
sets and computer laboratory exercises using Matlab.
(Click here to access the course
webpage.)
MAS 281 Complex Methods for the Sciences
The discovery of the imaginary number i opens the mind to a host of new mathematics involving the complex plane
and complex analysis. Closely associated with such advancement in mathematical thought is the development of the
theory of power series. The Fourier series and Fourier analysis are prime examples as their presence is almost
ubiquitous in the physical sciences. In the last part of the course, the student will be introduced gradually
to the world of partial differential equations and how that engenders various useful special functions.
(Click here to access the course
webpage.)
November 2004 - present
(1) Numerical weather prediction in Southeast Asia
This is work done in collaboration with
Temasek Laboratories @ Nanyang Technological University
(TL@NTU),
in continuation of the work begun in its sister institute, Temasek Laboratories @ National University
of Singapore (TL@NUS). I am principal investigator of the Tropical Weather programme at TL@NTU. The aim of
the programme is to improve mesoscale weather forecast in Southeast Asia for Singapore.
(2) Pollutant mixing and transport in convective atmospheres
This is my new project: the objective is to study mixing and transport of tracers (e.g. pollutants)
within the surface boundary layer due to convective turbulence, as well as within the deep troposphere
by cumulus convection. I am working with a postdoc, Dr. Jayaraman Potty, who has much experience
in boundary layer and turbulent studies.
(3) Fundamental geophysical fluid dynamics
Lagrangian and Hamiltonian approaches to fluid mechanics is a subject that is highly mathematical in
nature. I have always been fascinated by it. I hope to make some headway into this area, especially
in collaboration with a PhD or MSc student.
November 2001 - October 2004
At Temasek Laboratories @ National University of Singapore, I was concerned with Numerical Weather Prediction and
Tropical Meteorology research. Our work involved the
verification of the Coupled Ocean/Atmosphere Mesoscale Prediction System in Southeast Asia.
In particular, I was also working with Prof Lim Hock
on the rare case of tropical cyclone Vamei that landed 150km from Singapore in Dec 2001.
I also studied the dispersion of haze in Southeast Asia in collaboration with
Institute of High Performance Computing (IHPC).
May 2001 - August 2001
In Paris, I was working with Dr. Bernard Legras
at LMD on the problem of transport and
mixing in the stratosphere. Large-scale organized circulation in the winter mid-latitudes
generates
chaos in the Lagrangian flow. Based on available theory in the literature, we computed
hyperbolic and elliptic trajectories from the data analyses of the European Centre for
Medium-Range Weather Forecasts. Hyperbolic trajectories indicate regions of enhanced mixing
while elliptic trajectories represent barriers to mixing. Thus, our work examines the tracer
transport patterns in the stratosphere. A paper Koh and Legras (2002)
has since been published showing our results.
June 1998 - April 2001
My Ph.D. research was carried out in the Program for Atmosphere, Oceans and Climate at MIT,
under the supervision of Prof. Alan Plumb.
The research topic was on the general circulation and tracer transport in the
mid-latitude troposphere. My focus was on the role of the surface-branch circulation
in the transport of momentum, heat and long-lived chemicals. I first extended the isentropic
zonal average formalism to consistently incorporate the
surface boundary condition. The extended formalism was then applied to diagnose a
"stripped-down" general circulation model, obtained from Princeton University's
Geophysical Fluid Dynamics Laboratory (GFDL). The thesis Koh (2001)
qualifies and alters to some extent our understanding of the surface-branch circulation
in relation to recent ideas put forth in the literature. It also shows that the
surface-branch circulation plays an important role in global-scale transport of
chemical pollutants. The work was presented at American Meteorological Society's
14th Conference on Atmospheric and Oceanic
Fluid Dynamics in June 2003 (see Koh and Plumb (2003)).
A paper Koh and Plumb(2004) on the structure and dynamics
of the near-surface circulation has since been published.
July 1997 - May 1998
My involvement with stratospheric tracer transport began in my second year at MIT, with
Prof. Alan Plumb in the Program for Atmospheres,
Oceans and Climate. We studied the problem of transport across the edge of the polar vortex
that is characteristic of wintertime stratospheric circulation. The method we
used for quantifying the cross-edge transport is based on theoretical work by
Stephen Wiggins. We applied the method
in a barotropic model of the polar vortex that exhibits the same Rossby-wave breaking
mechanism of transport as the stratospheric vortex. Our findings are summarized in
Koh and Plumb (2000).
- click on the titles for further information.
Koh, T. Y. and R. A. Plumb (2004), "Isentropic zonal average formalism and the near-surface circulation ", Quarterly Journal of the Royal Meteorological Society, Vol. 130, Part A, No. 600, pp. 1631-1654.
Koh, T. Y. and R. A. Plumb (2003), "Isentropic zonal average formalism and the near-surface circulation ", Proceedings of the 14th Conference on Atmospheric and Oceanic Fluid Dynamics, organized by American Meteorological Society, 9-13 June 2003.
Koh, T. Y. and B. Legras (2002), "Hyperbolic lines and the stratospheric polar vortex", Chaos: An Interdisciplinary Journal of Nonlinear Science, Vol. 12, No. 2, pp. 382-394.
Koh, T. Y. (2001), "Isentropic diagnostics of mid-latitude circulation and transport", Ph.D. thesis, Massachusetts Institute of Technology, USA, 288pp.
Koh, T. Y. and R. A. Plumb (2000), "Lobe dynamics applied to barotropic Rossby-wave breaking", Physics of Fluids, Vol. 12, No. 6, pp. 1518-1528.
With the serious bit over, perhaps we can indulge ourselves in some
idle chatter. I think I shall tell you some of things that I enjoy
during my spare time. Yes?
Or perhaps, you would like to browse through my photo gallery ?
Otherwise, thank you for visiting me at my home page. You have been
my number
visitor. Have a pleasant day!
 Email me
at [email protected] |
|
Koh, Tieh Yong Assistant Professor School of Physical & Mathematical Sciences Nanyang Technological University 1 Nanyang Walk, Block 5, Level 3 Singapore 637616 tel: +65 6316 2966 fax: +65 6316 6984 |
last updated 27 July 2005