1 / 29

Introduction GEOF110: Innføring i dynamikken til atmosfæren og havet

Introduction GEOF110: Innføring i dynamikken til atmosfæren og havet. Who’s Who. Assoc. Prof. Ilker Fer ilker.fer@gfi.uib.no Room 126 at GFI Assistant Sturla Svendsen sturla.svendsen@gfi.uib.no Room 103 at GFI Administration: Kristin Kalvik (Studiekonsulent) kristin.kalvik@gfi.uib.no.

lara-mays
Télécharger la présentation

Introduction GEOF110: Innføring i dynamikken til atmosfæren og havet

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. Introduction GEOF110: Innføring i dynamikken til atmosfæren og havet

  2. Who’s Who Assoc. Prof. Ilker Ferilker.fer@gfi.uib.no Room 126 at GFI Assistant Sturla Svendsen sturla.svendsen@gfi.uib.no Room 103 at GFI Administration: Kristin Kalvik (Studiekonsulent) kristin.kalvik@gfi.uib.no GEOF110, 2008

  3. Course Description • 10 Credits • Language: English (Norwegian if needed) • Contents: • introduction to the theory for motion in atm. and ocean. • governing equations • stability, diffusion, continuity, geostrophic winds/currents, circulation, vorticity • boundary layer of the atmosphere and ocean • surface gravity waves and internal waves • effect of the Earths rotation on the winds and currents • Assessment • Midway exam, written, 2 hours. Counts 20% on the final grade. • Final exam, written, 4 hours. Counts 80% on the final grade.   GEOF110, 2008

  4. Lærebøker • Pond and Pickard: Introductory Dynamical Oceanography Pensum: Hele boken unntatt Kap. 8.9-8.10, 9.5-9.6, 9.8-9.10, 9.12-9.13, 9.14.1, 11 og 12.10 • Tor Gammelsrød: Tyngdebølger, kompendium. Pensum: Hele (pdf on studentportal– but will be updated) • Wallace and Hobbs: Atmospheric science Pensum: Chapter 7 (pdf on studentportal) • Anbefalt tilleggsbok: • Atmospheric science; Wallace and Hobbs • Fluid Mechanics; P. Kundu • Ocean Circulation. (The Open University). GEOF110, 2008

  5. Connect to studentportal • Show member list • Show oppgaver list • Show timeline GEOF110, 2008

  6. Introduction • Describe and interpret the structure and evolution of the large scale motions in the atmosphere and the ocean • Dynamical Oceanography is concerned with the forces acting on the ocean waters and with the motions that follow. • Ultimate objective is to predict • Essence of dynamical approach is to deduce quantitative information about the movements of the ocean and air from mathematical statements of the basic principles of physics. • Oceanography  study of ocean Physicists  study of distribution of T,S, density, etc., water masses, the motions of the ocean in response to forces acting on it. GEOF110, 2008

  7. Typical questions: Why are large scale mid-lat surface circulations are CW in NH and CCW in the SH? Why are these narrow and swift at the western sides (Gulf Stream, Kuroshio etc.) but broad and slow elsewhere? What is distribution with depth of ocean currents? Why is the circulation around Antarctica is eastward? What are the mechanisms of transfer of momentum and energy between atmosphere and the ocean? What are the characteristics and causes of surface and internal waves? What is the role of turbulent motions in the oceans? GEOF110, 2008

  8. Overview of Geophysical Scales • Radius of the Earth = 6371 km • Mean depth of the ocean = 3.795 km • Area of ocean surface = 3.61  1014 m2 • Area of ice sheets and glaciers = 1.62  1013 m2 • Area of sea ice (March) = 1.75  1013 m2 • Area of sea ice (September) = 2.84  1013 m2 • Volume of the ocean = 1.37  1018 m3 • Mass of the ocean = 1.4  1021 kg • Mass of the atmosphere = 5.3  1018 kg • Mass of water in lakes and rivers = 5.0  1017 kg GEOF110, 2008

  9. GEOF110, 2008

  10. GEOF110, 2008

  11. Zonally Averaged Radiative Balance Excess of radiation in the tropics.Deficit in middle and high latitudes. The atmosphere/ocean system is forced to move about by this imbalance, and bring heat by convection/advection from equator to the poles. GEOF110, 2008

  12. Ocean is Deep • Left: Histogram of elevations of land and depth of the sea floor as percentage of area of Earth • Right: the hypsographic curve [from R.H.Stewart (2005), Introduction to Physical Oceanography] GEOF110, 2008

  13. Peak: 26x1015 m3 Pacific Bottom Water Indian Bottom Water North Atlantic Deep Water South Atlantic Bottom Water Worthington (1981) T-S range COLD!! Major water masses of the ocean have a small T-S range GEOF110, 2008

  14. Oceanic Heat Transport Ocean transports about 50% of the poleward flux in the A/O system. Heat transport in the ocean is done by both wind-driven and THC. Crude heat transport estimate for meridional volume flux of 20 Sv, deltaT=20deg is 1000x4000xdTxUV=1.6x10^15 W (1.6PW). GEOF110, 2008

  15. Temperature, Salinity, Density GEOF110, 2008

  16. GEOF110, 2008

  17. Thermohaline Circulation • Thermo (heating/cooling) + haline (freshening/salinification) • An overturning circulation – warm water flows poleward near the surface and cold/dense water sinks and flows equatorward in the interior. • Time scale? • Poleward transport of heat? • Overturning of the Atlantic THC? • Average heat flux to the atmosphere from warm water flowing North? • Why is the upper/northern part of the Atlantic THC water salty? • Role of thermal vs. haline forcing on THC? GEOF110, 2008

  18. The Great Ocean Conveyor Belt GEOF110, 2008

  19. (Schmitz, 1996) GEOF110, 2008

  20. (From K. Heywood) GEOF110, 2008

  21. Southern Ocean THC (Speer et al., 2000) GEOF110, 2008

  22. S-N Atlantic Ocean • Cold AABW fills the abyss • Fresh tongue of AAIW • Saline tongue of NADW • Saline signature of MOW • Dense waters formed circum-Antarctica have no obstacle • Dense waters formed circum-Arctic, circulate and overflow GSR. GEOF110, 2008

  23. External forcing… Moon [3.2 TW] Sun [0.5 TW] Wind [1.2 TW] Earth tide [0.2TW] Surface tide [3.5 TW] Atm. tide [0.02 TW] Internal tides IW and deep turb. [0.2 TW] Local turbulent patches [0.7 TW] 1 TW = 1012 W Dissipation at coast [2.6 TW] Dissipation to balance deep ocean mixing [2.1 TW] Munk & Wunsch (1998) GEOF110, 2008

  24. Mean winds for July GEOF110, 2008

  25. A low-pressure system causes convergence and lifting of the air mass at the centre of the depression. As the air is lifted, it cools, and water condenses out to form clouds. The latent heat released by the condensing water warms the cloud and strengthens the convective motion. Generation of tropical cyclones requires SST> ~26C. Saturation vapour pressure increases dramatically with temperature, thus very high rates of evaporation occur over the warm tropical ocean. Evaporation rate depends on the air-sea temperature difference and wind surface wind speed. L Sea Surface Temperature 35C -2C Dramatic Example of Air-Sea Interaction: Tropical Cyclone GEOF110, 2008

  26. The enhanced convective lifting deepens the depression, increasing in-flowing surface winds, and thus increasing the surface flux of water vapour. Initially the convection takes the form of a collection of individual thunderstorms, but as the circulation strengthens they become organised into a single tropical storm This positive feedback process causes the intensity of the circulation to increase exponentially until… …Eventually the loss of kinetic energy by surface friction balances the generation by buoyant convection. The hurricane can be maintained until it loses the strong surface forcing – moving over land, or colder water GEOF110, 2008

  27. Cold water trails in the wakes of hurricanes Fabian & Isabel 2003/08/27-2003/09/23 NASA/Goddard Space Flight Center Scientific Visualization Studio Data from : Aqua/AMSR-E, GOES/IR4, Terra/MODIS http://svs.gsfc.nasa.gov/vis/a000000/a002800/a002824/index.html GEOF110, 2008

  28. A mature tropical cyclone can produce surface sensible heat fluxes of ~500 W m-2 and latent heat fluxes of 1000 Wm-2. All this energy is extracted from the ocean, resulting in a significant cooling of the ocean surface mixed layer. The sea surface temperature (through translucent cloud imagery) is reduced by ~5-10C in the wake of hurricane Katarina (August 2005). GEOF110, 2008

More Related