Visting Scholar
Environmental Fluid Mechanics Lab
Yang & Yamazaki Environment and Energy Building, m/c 4020
473 Via Ortega
Stanford, CA 94305
Tel: (408) 4315433
Email:sankara68(@)yahoo.com
Sankar is a visiting scholar with
Oliver Fringer's Group at Stanford University.
Sankar obtained a Ph.D. in Ocean Engineering
from the University of Rhode Island, and received a Master of Science in Hydraulic Engineering from the Indian Institute of Technology, Madras (IITM).
Sankar worked as a hydrodynamic modeler from 2001 to 2008, at Applied Science Associates, a marine environmental modeling company based in Rhode Island.
Research Interests
Dynamics of low frequency fluctuations in San Francisco Bay during upwelling
In this project, the dynamics of low frequency fluctuations in San Francisco Bay is studied
using observations and SUNTANS model. The low-frequency fluctuations in estuaries can be
due to local winds, river inflow and coastal upwelling. Detailed analysis of oceanographic
observations during the 1999 upwelling event has been carried out to understand the
low-frequency dynamics in the bay. The sources of low-frequency fluctuations in the bay
are studied using SUNTANS model forced with different forcing functions.
In the next phase of the study, a ROMS model for the Northern California shelf will be
used to generate the boundary conditions for the SUNTANS model for the bay.
A principal component analysis is carried out on the observed currents to distinguish the
barotropic and baroclinic components of the low-frequency fluctuations. The source of the
barotropic low-frequency fluctuations is then determined with the SUNTANS model which
is forced using local winds and offshore low-frequency surface observations. The SUNTANS model predictions for low-frequency currents show good
comparison with the observed barotropic currents in the Bay.
Large seasonal phytoplankton blooms began occurring in San Francisco Bay in 1999, despite
decreasing nutrient inputs into the Bay during the preceding two decades. Cloern et al.
attributes the sudden biological community changes occurring during the last decade in
San Francisco Bay over three trophic levels to the changes in the California Current system,
characterized by increased upwelling intensity, amplified primary production, strengthened
southerly flows, and fast filtration removal of photoplankton cells by bivalve mollusks.
A better understanding of the low-frequency circulation in the Bay would greatly help to
understand the effects of upwelling on the biological productivity in the bay.
Figure shows the depths on top of SUNTANS predicted steady depth-averaged currents in South San Francisco bay due to a
steady south-westward wind. The currents in the shallow shoals flow with the wind,
while the flow is against the winds in the deeper channels. The simulations also show that
the local winds and bathymetric variability drive transverse circulation in the Bay similar to
the topographic gyres seen in lakes.
Figure shows the depths on top of SUNTANS predicted steady depth-averaged currents in North and Central bays due to a
steady south-westward wind. The currents in the shallow shoals flow with the wind,
while the flow is against the winds in the deeper channels. The simulations also show that
the local winds and bathymetric variability drive transverse circulation in the Bay similar to
the topographic gyres seen in lakes.
Related publications
Sankaranarayanan, S., and Fringer, O. B. (2010) Dynamics of Low-frequency fluctuations in
San Francisco Bay due to upwelling, accepted for presentation at the session on Prediction of
Multi-Scale/Multi-Physics Coastal Ocean Flows Using Model Coupling Approaches, 2010 American
Geophysical Union fall meeting held at San Francisco. 13-17, Dec 2010.
Selected Publications
Sankaranarayanan S (2006) “ Modeling tide and wind-induced circulation in Buzzards Bay",
Revised manuscript submitted to Estuarine,Coastal and Shelf Science,
[buzzards.pdf]
Sankaranarayanan S and Matthew C Ward (2006) Development and Application of a three-dimensional orthogonal
coordinate hydrodynamic model, Continental Shelf Research, 26, pp. 1571-1594. [ortho.pdf]
Sankaranarayanan S (2005) “ A 3D boundary-fitted barotropic hydrodynamic
model for the New York Harbor Region", Continental Shelf Research, 25, pp.2233-2260
[newyork.pdf]
Sankaranarayanan, S and Spaulding, M. L (2003) “
A study of the effects of grid non-orthogonality in the boundary-fitted
coordinate system", Journal of Computational Physics", 184(1), pp.299-320,
[pap1.pdf]
Sankaranarayanan, S and Spaulding, M. L (2003) “ Dispersion and Stability
Analyses of the Linearized Two-dimensional Shallow Water Equations in Boundary-fitted coordinates",
acccpted for publication in International Journal for
Numerical Methods in Fluids [ijnmf.pdf]
Sankaranarayanan S and McCay, D F (2003) “ Three-dimensional
hydrodynamic modeling of tidal circulation in Bay of Fundy",
ASCE Journal of Waterway, Port, Harbor, Coastal and Ocean Engineering, 129(3)
[bof_jh1.pdf]
Sankaranarayanan S and McCay, D F (2003) “ "Application of a two-dimensional depth-averaged hydrodynamic model',
Ocean Engineering.
Sankaranarayanan, S and Spaulding, M. L (2003) “ Dispersion and Stability
Analyses of the Linearized Two-dimensional Shallow Water Equations in Cartesian
Coordinates"
Spaulding, M. L., S. Sankaranarayanan, L. Erikson, T, Fake, and T. Opishinski, 1998. COASTMAP, An
integrated system for monitoring and modeling of coastal waters: Application to Greenwich
bay, Proceedings of the 5th International Conference on Estuarine and Coastal
Modeling, American Society of Civil Engineers, Alexandria, VA, October 22-24, 1997,
pp.231-251
Sankaranarayanan,S., Shankar, N. J., and Cheong, H. F. (1998) “Three-dimensional finite difference
model for transport of conservative pollutants”, Journal of Ocean Engineering,
25(6), 425-442.
Shankar, N. J., Cheong, H. F., Sankaranarayanan, S. (1997) “Multilevel finite difference model for
three-dimensional hydrodynamic circulation”, Journal of Ocean Engineering, 24(9),785-81
Sankaranarayanan, S and H. Suresh Rao, (1996) "Finite element analysis of free surface flow
through gates", International Journal for Numerical Methods in Fluids, 22(5),
375-392.
Sankaranarayanan, S., Cheong, H. F., and Shankar, N. J. (1996) “Discussion on the paper
titled 3D Model of estuarine circulation induced by surface discharges,Journal of Hydraulic Engineering, ASCE,
122(7), 420-422
Suresh Rao, H and S. Sankaranarayanan, (1995)Location of water table by using FEM and electrical
analogy experiments, Ground Water, 33(3), 372-377.
Suresh Rao, Hand Sankaranarayanan, S(1992) Discussion on the paper, Solving turbulent flows
using finite elements”, Journal of Hydraulic Engineering, ASCE,118, 1698-1700.
