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In Situ Data Collection Currents

In Situ Data Collection Currents. ADCP. Benefits of In Situ Collection. Large amounts of data from a single point over a designated period High degree of thoroughness Real time data on tides, currents and winds Reliable, Low Cost data (comparatively)

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In Situ Data Collection Currents

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  1. In Situ Data CollectionCurrents ADCP

  2. Benefits of In Situ Collection • Large amounts of data from a single point over a designated period • High degree of thoroughness • Real time data on tides, currents and winds • Reliable, Low Cost data (comparatively) • Not dependant on a researcher being able to get out to sample • Long term records are good for forecasting and correlative studies

  3. www.mymobilebay.com • 3 sites at the head and middle of the bay and one at DISL • Established 2004 • Standard Meterological Data • Air temp • Barometric pressure • Relative humidity • Wind direction and speed • Precipitation • Hydrographic Data • Water temp • Salinity • Water Height

  4. http://marine.rutgers.edu/mrs/coolresults/1999/goos/f_goos.htmlhttp://marine.rutgers.edu/mrs/coolresults/1999/goos/f_goos.html • Ocean observation networks for ports, estuaries and the open shelf are currently operating or are being constructed at numerous locations around the country. • Both long-term and real-time applications. • Advancements in sensor and platform technologies, multiple real-time communication systems for transmitting the data, and the emergence of a universal method for the distribution of results via the World Wide Web. • Problems: operational support, instrument calibration, bio-fouling, power requirements, and data management. • Future recommendations: development of partnerships, long-term support mechanisms, and a new generation of support personnel that fosters the formation of a National distributed observation network.

  5. In-situ Data Example • One mooring station (30°05.410´N and 88°12.694´W) has been maintained to collect time-series data with approximately monthly maintenance surveys. • surface CTD, T1, T2, T3, T4, T5, T6, T7, T8, T9, TD, bottom CTD, and ADCP • meteorological data (winds and air temperature) at a nearby NDBC stations, Dauphin Island (DPIA1), were downloaded from the NDBC website.

  6. Meteorological (wind and air temperature) and temperature, salinity, σt, and water depth in July 2006.

  7. Isopleths of temperature in the time-depth domain in July 2006

  8. ADCPAcoustic Doppler Color Profiler • Measures water velocity and different depth levels using the Doppler shift of sound waves • Internally combines and processes velocities into a vertical profile of water velocity • Can be deployed for a few hours or a few months • Battery life • Memory capacity • Biological fouling

  9. Doppler Effect • Observed whenever the source of waves is moving with respect to an observer. • Apparent upward shift in frequency for observers towards whom the source is approaching and an apparent downward shift in frequency for observers from whom the source is receding. • It is important to note that the effect does not result because of an actual change in the frequency of the source.

  10. Doppler Effect The net effect of the motion of the bug (the source of waves) is that the observer towards whom the bug is moving observes a frequency which is higher than 2 disturbances/second; and the observer away from whom the bug is moving observes a frequency which is less than 2 disturbances/second

  11. Emits a “ping” (sound) and listens for the echo of that sound Sound is reflected off particles in the water (suspended solids and plankton) Key Assumption – These particles on average move at the same horizontal velocity as the water A Doppler shift in the frequency of the ping occurs Transducer records the returning echos Uses the shift in frequency to calculate the speed and direction of the particles Time determines the distance from the transducer and then can be directly related to water depth ADCP

  12. Vertical Velocity Profile An instantaneous vertical velocity profile showing both speed and direction in earth coordinates. In this the total depth is approximately 20m with velocity measurements taken every .5m.

  13. A time series plot of ADCP velocity data - five months. • The small top contour shows the velocity magnitude over the entire deployment. • Bottom is a subset of the deployment from 12/5/05 to 1/6/06. • ADCP is on the bottom looking up to a depth of approximately 20m • Distinguish the surface by the higher currents at 20m (the velocities above 20m on the contour are a result of double reflections and are not true velocities). • To the left of the contour, is a plot of the velocity profile of one measurement period (shown by the arrow).

  14. Uses of ADCP Data • Track movement of the sea bottom (deployed from the surface) • Corrects for relative movement of the ADCP through the water • Can be deployed on a moving platform • Discharge from boats • River flow characteristics • Jellyfish?

  15. Function: Transport Mechanism Mixing Mass Balance Practical use: Engineering Considerations Erosion Outfalls Locate lost things Noted by: Units are usually cm/sec Direction is always given as direction TOWARDS which the current flows Currents

  16. Kinds of Currents • Distribution of Density • Same as movement of air from high pressure to low pressure • Gulf stream, Kuroshio, Benguela • Deep circulation is all density driven • Wind Stress • Because of frictional forces • Friction plus Coriolis in N hemisphere results in net transport to the right • Upwelling • Tidal Currents • Results from progression of tidal wave

  17. Lagrangian Method Path followed by each fluid particle is stated as a function of time Follows an individual parcel of water Drift Methods Drogue – attached buoy and passively drift with currents “Holey Sock” – used to test Ekman Spiral Surface drifters/ seabed drifters Dye Study Measurement Methods

  18. Measure Methods (con’t) Eularian Method Velocity (speed and direction) is stated at every point in the medium – measured at a stationary point as current passes Measured with: • Mechanical Meters • Electromagnetic meters • Acoustic Current Meters • Radar – both land and satellite based • Sends out electromagnetic waves and measures reflected energy from surface waves • CODAR – coastal ocean doppler radar

  19. Satellite-tracked drifter“holey-sock” • 10 meter-long by 1 meter-diameter "holey-sock" of strong nylon cloth held open by a series of steel hoops. • The center is set at the depth where scientists want to monitor water movements. • The sock is connected by the necessary length of cable to a surface buoy which transmits its location to the GOES satellite system. • The strobe light is to warn ships of its presence. The transponder and strobe are battery operated and can last many weeks • Deployed for specific experiments and then recovered by the ship. • The surface buoy has a low profile to minimize the influence of wind on where the drifter goes.

  20. Moored Current Meter • Can accommodate many instruments • current meters • temperature and salinity recorders • chlorophyll measurement devices (fluorometers) • Sub-surface buoy and elastic tether keep the wire taut • Surface buoy transmits data to land via satellites • store information from the attached instruments and also let ships know there are instruments in the water • The satellite passes over the buoy twice per day • Radar reflectors and lights help to prevent collisions from ships • Many of these buoys are kept in place for about a year, which allows for remote monitoring

  21. Moored Buoy The OrCOOS (Oregon Coastal Ocean Observing System) buoy contains an array of environmental sensors in the air and through the water column that detects changes in wind, oxygen, temperature, ocean currents and other indicators of ocean change

  22. Robots Scientists measuring ocean currents and other vital aquatic data have begun testing a totally sustainable robot propelled by temperature differences in the water. Other than a small battery used to transmit data back to the mother ship, it operates solely on energy already in the ocean — opening a new door to ocean monitoring. The U.S. has started using the gliders in the Caribbean to measure currents around the Virgin Islands and plans to deploy them in the Northern Atlantic and the Pacific.

  23. Sea Surface Temperature sea surface temperature as a means of tracing the flow of water

  24. Nike Method! 60,000 Nike shoes spilled from a storm-tossed cargo ship in the northeastern Pacific in May 1990. Six months to a year later, beachcombers from British Columbia to Oregon began to find shoes. Oceanographers constructed a computer model that predicted the shoes' route. In 1993, shoes were found in Hawaii. If the shoes complete the gyre's circuit, they will turn up in Japan and the Philippines, and in 1996 or 1997 again wash up on North American shores

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