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R/V ARANDA – A MOVING PLATFORM FOR INTEGRATED MULTIDISCIPLINARY
OBSERVATION SYSTEMS AND RESEARCH
Riikka Hietala, Kimmo Tikka, Heidi Pettersson, Matti Perttilä
Finnish Meteorological Institute, Erik Palmenin aukio 1, P.O.Box 503, FI-00101 Helsinki Finland
Tel. +358 9 19296430, Fax. +358 9 19295703, E-mail [email protected]
ABSTRACT
A moving platform – a research vessel – makes possible to observe an open sea environment widely
and during all seasons. In addition to the permanent equipment onboard a research vessel offers a
base and an infrastructure for special instruments when needed.
R/V Aranda is a modern, ice-reinforced research vessel for year-round multidisciplinary marine
research including physics, chemistry, biology and geology of the sea and marine meteorology.
This paper is focused to present R/V Aranda’s equipment related to marine meteorology and physical
oceanography. Special attention is paid to an integrated research on CO2 related processes in marine
environment.
1. INTRODUCTION
The oceans are an important part of the global weather system. The ocean circulation, driven by the
winds, redistributes the heat stored to the oceans. The oceans are an important sink for the carbon
dioxide. Also small basins like the Baltic Sea affect the climate of the surrounding land areas. Many of
the processes, e.g. the mixing of the water masses and the processes at the sea-atmosphere
interface, are similar regardless of the size of the basins.
R/V Aranda is equipped for biological, physical, chemical, marine meteorological and geological
research. She has a wide range of scientific equipment, well-equipped laboratories and facilities for
mooring operations. The integrated data management system improves the performance of the work
onboard and assures the consistency, quality and proper storage of the data. The infrastructure
facilitates also the implementation of new temporary instruments needing e.g. navigational data.
2. THE SHIP
R/V Aranda (Figure 1) was launched in Helsinki in June 1989 and she was renovated thoroughly in
year 2007. The length of the vessel is 59,2, the beam 13,8 m and the gross register weight 1734 GT
(Itämeriportaali, Aranda 2010). R/V Aranda is equipped with an A frame and cranes for mooring
operations. The manoeuvrability of Aranda has been dimensioned for demanding research work, the
ship being able to stay exactly in position at a station with dynamic positioning (DP) system.
The number of crew members is 12-13 and the accommodation capacity of the research staff is 25
persons. Drinking water can be purified from seawater using reverse osmosis system and a biological
wastewater treatment facility also enables 60 days’ extreme endurance at sea.
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Figure 1. Research vessel Aranda
Aranda was planned for the Baltic Sea research, but in principle, she is able to operate in all seas.
She has visited twice the Antarctic and several times the Nordic Seas. She is able also to work in ice
and nearly every year she has been a base for studies on the ice-covered sea.
Finnish Environment Institute (SYKE) is the owner of R/V Aranda, but she is also used by the Finnish
Meteorological Institute. Cruises are often common and there are often participants from other
institutes, also outside Finland.
3. SCIENTIFIC EQUIPMENT ONBOARD R/V ARANDA
The vessel is equipped with a comprehensive range of sampling equipment for taking water and
sediment samples and collect phyto- and zooplankton and benthic animals etc. Well-equipped
biological and chemical laboratories enable onboard sample analysis. SYKE Marine Research
Centre is a testing laboratory T040 (EN ISO/IEC 17025) accreditated by FINAS - Finnish Accreditation
Service (MIKES 2010) and most routine sampling and analysis methods fulfil the accreditation
requirements (Itämeriportaali, 2010).
Weather station
The weather station is a modified MAWS of Vaisala (Figure 2).The system includes two QML102loggers. Data communication is both-way between the navigation system and MAWS. The weather
station receives navigational data (ship speed and direction; ship’s heading; latitude and longitude)
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from the navigation system and sends all data forward in the NMEA-format with 10 s interval to
Aranda weather server where all data is stored to the AWC database.
The weather station measures and collects data from various sensors and makes calculations from
the measured data. Meteorological sensors measures air temperature, air pressure, relative humidity,
wind speed and direction, solar radiation and detects precipitation. Most sensors are installed on the
both sides of the ship. The software includes wind and temperature selection modules for the
windward sensor selection thus avoiding distortions caused by the ship to the observations. There is
also an additional weather station in the foremast which can be used with low ship’s speed. R/V
Aranda is also equipped with a DigiCora sounding system which has been used on the marine
meteorological research cruises. In addition the weather station collects sea surface temperature and
salinity data. The hull thermometer measures water surface temperature and the flow-through system
enables continuous measurement of sea water conductivity and temperature (from the depth of 4 m)
and thereby calculation of salinity.
Figure 2. The weather station of R/V Aranda.
Physical oceanography
The primary tool for determining physical properties of sea water is CTD (an acronym for Conductivity,
Temperature, and Depth). Onboard R/V Aranda a SeaBird911plus CTD is used to measure vertical
profiles of electrical conductivity, temperature, dissolved oxygen content and fluorescence (Chl-A)
versus pressure (i.e. depth). Salinity and density are calculated from the measured parameters. R/V
Aranda’s CTD system includes the SBE 32 Carousel water sampler with 12 bottles for water sampling.
FMI Observation Services is a testing laboratory T258 accreditated by FINAS (MIKES 2010) and the
CTD method onboard Aranda includes in the scope of accreditation.
R/V Aranda has a hull-mounted Acoustic Doppler Current Profiler, Ocean Surveyor 75 kHz from
Teledyne RDI, for measuring currents below the vessel. Continuous sea surface temperature and
salinity data are measured by the hull thermometer and the flow-through system. R/V Aranda has also
a towed CTD which can be used when the ship is cruising at a lower speed.
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Carbon dioxide measurements on board the RV Aranda
The direct measurements of the carbon dioxide flux in the atmosphere are not yet common and thus
the flux is usually calculated from the difference between the partial pressure of carbon dioxide in the
water and in the air using parameterisation of the transfer velocity. Sea state has an important role in
the exchange. An on-board system of measuring both the surface water partial pressure of CO 2 and
the air – sea CO2 flow and other relevant parameters in pure marine conditions was constructed
onboard R/V Aranda. It has been tested in different sea areas and seasons in 2005 – 2009 in the
Baltic Sea. simultaneous measurements were carried out on a permanent buoy system.
Measuring system for exchange processes between the air and sea
The ship is equipped with a measuring system for fluxes of the atmospheric CO2, momentum, heat
and moisture, the waves and subsurface turbulence (Figure 3 and 4). The experimental arrangement
is following:
Figures 3 and 4. The bow of R/V Aranda with the instrumentation for CO₂ flux studies
The bow mast of the vessel is equipped with a sonic anemometer Metek USA-1 for measurements of
the wind components and with a Li-7500 open path CO2/H2O analyzer to record the fluctuations of the
humidity and carbon dioxide. These sensors are installed at two heights. The structure of the bow and
the mast are such that there are no significant obstacles for the air flow. The bow of the vessel is
equipped with a down looking wave radar Miros Range Finder. Directional wave measurements are
made with an array of wave staffs deployed from the boom. The newest instrument in the system is
Vectrino for measuring the turbulence just under the sea surface. Additional wave measurements are
usually obtained from free-floating Directional Waverider in the vicinity of the vessel.
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To get reliable measurements from a moving platform, the motions of the platform have to be
recorded. The motion sensor MRU-6 is mounted below the sonic anemometer and the CO2 detector.
MRU-6 measures the three components of acceleration and the three components of the rotational
motion. During the measurements the vessel is kept in one position with small corrections of the
orientation to keep the bow against the wind direction with an accuracy of +/- 20 degrees. After
synchronizing the time series of the three sensors they must be corrected for the motions of the ship.
The partial pressures of carbon dioxide in sea water
The partial pressure of carbon dioxide pCO2 in sea water can measured on board during the cruises
by means of an underway system with continuous equilibration. The system follows the method
described by Körtzinger et al. (1996). At cruising speed, the water flow is ensured either by ship’s flowthrough pump, of which a small (350 – 450 mL/min) side flow is taken into the system. The pump is
positioned at 4 m depth. During station periods, the flow can be switched to use a submersible pump,
allowing for depth profile to be monitored (surface – 10 m).
Figure 5 (left). The flow-though system for measuring pCO2 in the sea water.
Figure 6 (right). The pCO2 distribution in the surface layer of the Baltic Sea in February 2009 (Riga
Bay data from March 2009). Units in µatm.
The water flow is directed into an equilibration chamber with a volume of ca. 250 mL. Air flow (250 –
300 mL/min) is introduced into the chamber through a grid, producing small air bubbles for quick
equilibration. The equilibration is further enhanced by means of strong mixing with a magnetic stirrer.
The equilibrated air is then led for pCO2 measurement by means of a LiCor 6262 non-dispersive
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infrared detector. Both the in situ temperature and the equilibrator temperature are continuously
recorded, and the raw data is corrected to in situ temperature (Takahashi et al., 1993). The system is
calibrated daily against certified calibration gases (Aga).
The estimated uncertainty of the carbon dioxide partial pressure determination is ca. ± 1 µ atm, as
based on the calibration gases. However, the total uncertainty of the field determinations is difficult to
estimate. Several repeats have yielded the uncertainty of ± 1 µ atm at station periods when the
submersible pump is in use, but during the cruise periods the uncertainty is probably higher but
difficult to evaluate because of the constantly changing water masses.
One example of the measurement results is shown in Figure 6.
Data management system
A scientific data management system of R/V Aranda is highly automated and integrated modular
system. It covers all steps from the cruise planning via data collection, storage and quality control to
the cruise reporting. In the core there are three databases, ArandaLIMS (laboratory management
system), SUMPPU (physical, chemical and biological data) and AWC (meteorological database),
which have replicas onboard and inlands. MyCruise cruise management software creates a metadata
interface within the system in a XML format. This XML file transforms from a cruise plan to a cruise log
during the cruise. Onboard information is delivered automatically to ArandaWiki and InfoChannel on
the TV network. Observations and the route of the cruise are daily send via GSM or satellite
communication to databases on land. Aranda internet pages are automatically updated from them.
4. SUMMARY AND OUTLOOK
The ship is very usable base to measure seasonal and regional variations of marine environment.
Movements of the ship and the flow distortions caused by the ship itself must be taken account when
measuring especially micrometeorological features.
There are many reasons why the need of research vessels is growing. The awareness of ocean’s role
has been increased with the progress of the climate change research and also due to recent marine
hazards e.g. tsunami generation, oil disasters. The need for ship-based calibration and validations of
observations provided with new technologies like autonomous moving vehicles, fixed stations and
remote sensing is increasing. More ship-time is demanded to launching and recovering autonomous
vehicles.
Demands for better ship-to shore satellite communication are increasing for providing real-time data
for weather forecast and sea models. There is also increased pressure to do multidisciplinary, multiinvestigator research to better understand the complicated interactions between physical, chemical
and ecological state of the sea and the climate conditions (e.g. ocean acidification, carbon and
biogeochemical cycling). Also economical reasons lead to develop research vessels towards
multipurpose construction. The latest modification plan for R/V Aranda concerns to enable mounting of
different hydro-acoustic sensors in the bottom of the hull without docking.
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References:
Itämeriportaali, 2010: The accreditated parameters of SYKE
http://www.itameriportaali.fi/en/tietoa/helcom_seuranta/en_GB/parametrit/
Itämeriportaali 2010: The R/V Aranda
http://www.itameriportaali.fi/en/aranda/aranda_matkat/en_GB/2010/
Körtzinger, A., Thomas, H. Schneider, B., Groanu, N., Mintrop, L and Duinker, J.C., 1996. At-sea
intercomparison of two newly designed underway pCO2 systems – encouraging results. Mar. Chem.
52, 133 – 145.
MIKES 2010 SYKE Marine Research Centre
http://www.mikes.fi/Scopes/T040_M13_2005.htm
MIKES 2010 FMI Observation Services
http://www.mikes.fi/Scopes/T258_A01_2010.htm
Pettersson, H., K.Kahma and M.Perttilä, 2008: Studying the carbon dioxide exchange in the Baltic
Sea.- SOLAS Newsletter, Issue 7, 8. www.solas-int.org.
Takahashi, T., Olafsson, J., Goddard, J.G., and Chipman, D.W., 1993. Seasonal variation of CO2 and
nutrients in the high-latitude surface oceans: a comparative study. Global Biochemical Cycles 7, 843 –
878.
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