General Description

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General Description

• Physical and biological processes are
  inter-related aspects that govern the
  productivity of marine ecosystems.
• Provides an introduction to the physical
  processes that control abundance of marine
  organisms in the ocean.
• Turbulence in surface and bottom boundary layers
  and its roles on the lives of plants and animals
  buoyancy- and wind-induced circulation, mixing,
  coastal upwelling/ downwelling processes, fronts,
  river plume, tides, internal waves, circulation
  and eddy and their effects on biological
  transport, primary production zooplankton, fish
  and the regeneration of nutrients
• NPZD (Nutrient, Phytoplankton, Zooplankton and
  Detritus) chemical-biological model mathematical
  and numerical techniques in the of coupled
  hydrodynamic-ecosystem model.

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Global distribution of chlorophyll averaged over
the period from 1 January 2002 to 28 February
2005 using data collected from MODIS on the Aqua
satellite. Chlorophyll values range from 0.01
mg/m3 (purple) to 60 mg/m3 (red). From NASA
Goddard Space Flight Center.
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Xie, L. and W.W. Hsieh, 1995
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Sun

Photosynthesis by phytoplankton
Currents, tides (also moon), turbulence and
stratification by heating or associated wind

• Alters boundary layers, stratification and
  euphotic layer, causes retention of planktonic
  organisms and modifies light penetration.
• 2. Transports nutrients and waste products,
  assists migrations, affects the rate of encounter
  between planktonic predators and their prey.
• 3. Rate of biological process is affected by T
  (C) and organisms colonizing is determined by v
  (m/s).

Passed from organism to organism by feeding
transfers
Food Web
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Multi temporal and spatial scales in physic and
biologic processes
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OSU
1mm10-3m
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Transfers of nutrients and waste products by
faster turbulent diffusion, mesoscale, upwelling,
eddy, front, surface and internal waves
Transfers of nutrients and waste products by eddy
turbulent diffusion,basin scale circulation,
plantary waves, tides
Transfers of nutrients and waste products by
molecular diffusion
Molecular
(m)
Internal Rossby deformation radius
h water depth ? water density O angular
velocity of earth rotation F latitute
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Temporal scales determined from organisms
days-1wks
Large marine mammal
Molecular
hours
Time scale
About 100 yrs
1-10 yrs
days
Increase fluctuations in number
Process of trophic transfer
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Turbulence, diffusion and boundary layers,
mixing, mixed layer
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Periods
Periods
rapidly varying turbulent component
slowly varying mean fields
Periods of u from a second (minimum) to tens
minutes (maximum). Size of u from a few
millimeters (µm) (minimum) to a few meters
(maximum)
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Laminar Flow and Turbulent Flow

• The terms laminar flow and purely viscous
  (molecular) flow are used synonymously to mean a
  fluid flow which flows in laminas or layers, as
  opposed to turbulent flow in which the velocity
  components have random turbulent fluctuations
  imposed upon their mean values.
• In general, increase the flow will change from
  laminar to turbulent.
• The effect of viscosity are still present in
  turbulent flow, but they are masked by much
  strong turbulence. The viscosity due to turbulent
  flow is sometimes called as turbulent viscosity.

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Sources of turbulent energy 1 Instability
induced by surface or internal wave
breakings, 2 Wind stirring at the sea
surface, 3. Velocity shear, 4. Strong
currents, meanders and eddies breakings.
Velocity shear
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DefinitionsViscosity, Friction and Ideal Flow

• Molecular Viscosity internal friction of fluid
  due to molecular motion, which causes it resist
  the tendency to flow. This comes to work when the
  scale of turbulence is
• lt 1mm.
• Viscous force, i.e. friction depends on the type
  of fluid and physical configuration or flow
  pattern (including both molecular and turbulent
  viscous force. The magnitude of latter is much
  larger).
• If the viscous force is negligible, the flow is
  defined as ideal flow or inviscid flow in which
  friction is precisely zero.
• A fluid with very small viscosity may behave
  quite differently to a (hypothetical) fluid with
  no viscosity at all.

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Reynolds number
viscosity coefficients
u velocity, d typical dimension,
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Table 2.1
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Diffusion-Viscosity

• Diffusion mixing of a property by the random
  motions of molecules (molecular diffusion) or of
  eddy (turbulent or eddy diffusion).
• Viscosity it is resistance force of the water,
  acts to resist the velocity. Its consequence
• is corresponding to the associated diffusion.

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Some Estimations

• Ficks Law to estimate the flux and time scale
  of a variable due to molecular diffusion

The length scale to diffuse
Coefficient of molecular diffusion1.5x10-9m2s-1

• Kolmogoroff Length length scale across the
  smallest eddy of smallest fluctuation.
• L(kinematic viscosity (molecular)/turbulent-ener
  gy dissipation)1/4

• Largest turbulent eddies to determine the
  vertical excursion of the small passive organisms
  being moved about by the turbulent flow
• Lb(turbulent energy dissipation/stratification

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(Bottom) Boundary Layer

• Solid boundary in which water movement is
  reduced.
• It reduces the exchange rate of molecules of
  O2, CO2, NH3 etc. with the ambient waters.

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Idealized case
Real case
No-slip boundary or u0 at solid surface