1 / 26

General Description

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.

moral
Télécharger la présentation

General Description

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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. AMCE608

  2. AMCE608

  3. 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. AMCE608

  4. AMCE608 Xie, L. and W.W. Hsieh, 1995

  5. AMCE608

  6. AMCE608

  7. 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 AMCE608

  8. Multi temporal and spatial scales in physic and biologic processes AMCE608

  9. OSU AMCE608 1mm=10-3m

  10. 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; ρ: water density; Ω: angular velocity of earth rotation; Φ: latitute AMCE608

  11. 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 AMCE608 Process of trophic transfer

  12. Turbulence, diffusion and boundary layers, mixing, mixed layer AMCE608

  13. 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) AMCE608

  14. Laminar Flow andTurbulent 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. AMCE608

  15. AMCE608

  16. 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 AMCE608

  17. AMCE608

  18. Definitions:Viscosity, 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 < 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. AMCE608

  19. AMCE608

  20. Reynolds number : viscosity coefficients u: velocity, d: typical dimension, AMCE608

  21. Table 2.1 AMCE608

  22. AMCE608

  23. 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. AMCE608

  24. Some Estimations • Fick’s Law: to estimate the flux and time scale of a variable due to molecular diffusion The length scale to diffuse Coefficient of molecular diffusion=1.5x10-9m2s-1 • Kolmogoroff Length: length scale across the smallest eddy of smallest fluctuation. • L=(kinematic viscosity (molecular)/turbulent-energy 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 AMCE608

  25. (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. AMCE608

  26. Idealized case Real case No-slip boundary or u=0 at solid surface AMCE608

More Related