NIB - MORSKA BIOLOŠKA POSTAJA PIRAN
What does the oceonographic buoy measure?
The oceanographic buoy is fitted with measurement instrumentation for the Marine Biology Station Piran of the National Institute of Biology . An acoustic current gauge is situated on the sea bed beneath the buoy to monitor currents.device (manufactured by Nortek , Norway) takes a current profile (at one meter depth intervals) and monitors sea floor temperature and relative changes in sea level (mainly due to tidal variation). An acoustic wind gauge (Gill instrument ), installed on the oceanographic buoy at approximately five meters above sea level, is used to measure winds. An electronic compass has been added to measure the minor position shifts of the buoy which is otherwise triply anchored. We have a web site which currently allows the wider public access to wind speed data. Other measurements will also beadded to this site in the near future. The oceanographic buoy will ensure an improved overview of sea conditions (principly currents and winds). It will contribute to improved safety for sea farers, to more efficient accident intervention and to more accurate assessment of the ecological impact of pollutants (for example in the spread of fuel slicks). Stainless-steel buoy Vida was manufactured and deployed in operation in 2008 by the company Manta d.o.o.
Oceanographic buoy is supported also by the Slovenian Environment Agency.
| Manufacturer, instrument | Quantity | Height above/below the sea-surface (m) | Sampling period (s) | Number of measurements / time unit | Quality control |
| VAISALA, HMP 45A | Air temperature and humidity | 5,0 | 10 | 6 / minute | YES |
| Gill Instruments, WindMaster Pro Ultrasonic Anemometer | Wind speed and direction | 5,0 | 0,1 | 10 / s | YES |
| Xsens Technologies, MTI XSENS KOMPAS | 3D compass | 5,0 | 10 | 10 / s | NO |
| VAISALA, GMP343 | CO2 in the air | 4,0 | 120 | 1 / 2 minutes | NO |
| LICOR, LI-190SL-50 | PAR | 4,4 | 0,23 | 4,26 / s | NO |
| SeaBird , SeaBird 16plus SEACAT | Salinity and temperature | -2,5 ± 0.2 | 300 | 1 / 5 minutes | NO |
| Wet labs, ECO Chlorophyll Fluorometer Chlorophyll-a (FL-CHL) | Chlorophyll concentration | -2,0 ± 0.2 | 300 | 1 / 5 minutes | NO |
| AANDERAA DATA INSTRUMENTS, Oxygen optode 3835 | Oxygen | -2,2 ± 0.2 | 60 | 1 / minuto | Control |
| AANDERAA DATA INSTRUMENTS, Oxygen optode 4835 | Oxygen | -22,5 ± 0,5 | 60 | 1 / minute | NO |
| Nortek, Acoustic currentmeter AWAC 600kHz z NIP | Currents | -2,5 ± 0,5 | 1 | 600 in the first 10 minutes in half-hour interval | NO |
| Nortek, Acoustic currentmeter AWAC 600kHz z NIP | Waves | -22,5 ± 0,5 | 1 | 1024 in next 1024 seconds in half-hour interval | NO |
| Nortek, Acoustic currentmeter AWAC 600kHz z NIP | Temperature | -22,5 ± 0,5 | 1 | 600 in the first 10 minutes in half-hour interval | NO |
A short description of data processing from the oceanographic buoy
- Wind, current and battery voltage data is received every half hour.
- Wind measurements are conducted continuously with a sampling period of 0,25 s.
Computed quantities from the received measurements :
- Average wind vector: the magnitude and direction of the vectorial average of instantaneous wind data
- Average wind speed: the arithmetic mean of instantaneous wind speeds
- Prevailing wind direction: the median value of instantaneous wind directions
- Minimal wind speed and direction
- Maximal wind speed and direction
- Wind stability: the ratio between the magnitude of the average wind vector and the average wind speed
- After all wind data has been received, the buoy also supplies particulars about battery voltage and a cluster of data from the sensors installed on the current-meter (temperature and pressure at the bottom plus speed and direction of currents at 2 m depth intervals.
The applied Beaufort scale has been taken from the web page at : http://www.unc.edu/~rowlett/units/scales/beaufort.html
