THESIS
2019
xi, 48 pages : illustrations (some color) ; 30 cm
Abstract
We conduct a numerical simulation on an idealized estuary-shelf system to investigate
submesoscale processes under multiple forcing of winds, buoyancy from river runoff and
tides. The system is analogue to physical settings of the Pearl River Estuary (PRE) and
adjacent shelf off Hong Kong. Based on Regional Ocean Modeling Systems (ROMS) of
primitive equations with turbulent closure scheme, the numerical model is implemented
in high horizontal resolution of 100 m x 100 m grid with open boundaries in a limited-area
computational domain. The model is forced by prevailing monsoon wind stress
and buoyancy from river discharge. By utilizing various combinations of physical forcing
and numerical implementations, we successfully simulate the submesoscale flow structures
characterized...[
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We conduct a numerical simulation on an idealized estuary-shelf system to investigate
submesoscale processes under multiple forcing of winds, buoyancy from river runoff and
tides. The system is analogue to physical settings of the Pearl River Estuary (PRE) and
adjacent shelf off Hong Kong. Based on Regional Ocean Modeling Systems (ROMS) of
primitive equations with turbulent closure scheme, the numerical model is implemented
in high horizontal resolution of 100 m x 100 m grid with open boundaries in a limited-area
computational domain. The model is forced by prevailing monsoon wind stress
and buoyancy from river discharge. By utilizing various combinations of physical forcing
and numerical implementations, we successfully simulate the submesoscale flow structures
characterized by horizontal length O(100)m and examine the response of estuarine
and shelf circulation to multiple forcing. In particular, we study the freshwater bulge,
frontal formation and estuary-shelf exchange under the influence of active submesoscale
processes in the system. The instability associated with submesoscale fronts induced
by river plume is closely bound to the interaction between wind-driven currents and
buoyancy effects. We found that submesoscale processes develop at the edge of the river
plume and they spread and intensify with time. This is because of underlying nonlinear
effects and unbalanced motions. This study develops a submesoscale-resolving numerical
model, and improves our understanding of the ocean circulation around the PRE by
identifying the underlying submesoscale processes unmentioned before.
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