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Ren-Chieh Lien

Senior Principal Oceanographer

Affiliate Professor, Oceanography





Research Interests

Turbulence, Internal waves, Vortical motions, Surface mixed layer and bottom boundary layer dynamics, Internal solitary waves, Small-scale vorticity, Inertial waves


Dr. Lien is a physical oceanographer specializing in internal waves, vortical motions, and turbulence mixing in the upper ocean and their effects on upper ocean heat, salinity, momentum, and energy budgets. His primary scientific research interests include: (1) upper ocean internal waves and turbulence, especially in tropical Pacific and Indian oceans, (2) strongly nonlinear internal solitary wave energetics and breaking mechanisms, (3) small-scale vortical motions, and (4) bottom boundary layer turbulence. He is especially interested in understanding the modulation of internal waves and turbulence mixing by large-scale processes, as well as the effects of small-scale processes and large-scale flows.

One of Dr. Lien most important findings is the strong modulation of turbulence mixing by large-scale equatorial processes, such as tropical instability waves and Kelvin waves, in the eastern equatorial Pacific. He is especially interested in small-scale, potential vorticity motions — the vortical mode, which operates on the same scale as internal waves — and their effects on turbulence mixing and stirring. Lien has led sea-going experiments in the Pacific and Indian oceans and the South China Sea, using a variety of instruments including microstructure profilers, Lagrangian floats, EM-APEX floats, and moorings. He also developed a real-time towed CTD chain system, designed to study small-scale water mass variability in the upper ocean at a vertical and horizontal resolution of O(1 m).

Lien mentors and supervises masters and doctoral students and postdocs. His research and experiments have been funded primarily by the National Science Foundation, the Office of Naval Research, and National Oceanic and Atmospheric Administration.

Department Affiliation

Ocean Physics


B.S. Marine Science, Chinese Culture University, 1978

M.S. Physical Oceanography, University of Hawaii, 1986

Ph.D. Physical Oceanography, University of Hawaii, 1990


Lateral Mixing

Small scale eddies and internal waves in the ocean mix water masses laterally, as well as vertically. This multi-investigator project aims to study the physics of this mixing by combining dye dispersion studies with detailed measurements of the velocity, temperature and salinity field during field experiments in 2011 and 2012.

1 Sep 2012


2000-present and while at APL-UW

Internal solitary waves and mixing

Lamb, K.G., R.-C. Lien, and P.J. Diamessis, "Internal solitary waves and mixing," in Encyclopedia of Ocean Sciences, 3rd, J.K. Cochran, H. Bokuniewicz, and P. Yager, eds., 533-541 (Academic Press, 2019).

19 Mar 2019

Vortical motion

Kunze, E., and R.-C. Lien, "Vortical motion," in Encyclopedia of Ocean Sciences, 3rd, J.K. Cochran, H. Bokuniewicz, and P. Yager, eds., 702-706 (Academic Press, 2019).

19 Mar 2019

Scaling of drag coefficients under five tropical cyclones

Hsu, J.-Y., R.-C. Lien, E.A. D'Asaro, and T.B. Sanford, "Scaling of drag coefficients under five tropical cyclones," Geophys. Res. Lett., EOR, doi:10.1029/2018GL081574, 2019.

More Info

4 Mar 2019

The forecast of tropical cyclone intensification is critical to the protection of coastlines, involving the complicated tropical cyclone‐ocean interaction. The wind of storms can force strong near‐inertial current via surface wind stress (often parameterized by a drag coefficient Cd), and then induce the upper ocean cooling due to the shear instability. The transferred momentum and reduced heat supply can both restrict tropical cyclones' development. In other words, the Cd can affect the prediction of momentum and thermal response under storms, and thereby the forecast on storm intensity. This study investigates the spatial variability of downwind drag coefficient Cd under five different tropical cyclones, by integrating the storm‐induced ocean momentum because previous results of Cd as a function of wind speed |U10| are scattered significantly at |U10|= 25–40 m/s. Here, larger Cd in the front‐right sector of faster storms than that of slower stoms is found, presumably due to the surface wave effect. A new parameterization of Cd using the surface wave properties under tropical cyclones is proposed, which largely improves the conventional parameterization of Cd(|U10|). Future studies on the tropical cyclone‐wave‐ocean interaction and storm intensification forecast will be benefited from this new parameterization.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center