Metadata Report for BODC Series Reference Number 664268

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

Originator's quality control comments for RIG#897/RCM#9631

Data supplied to BODC were accompanied by data quality notes from the Originator that detailed observations made when the data were processed and subsequent processing decisions. A summary of these notes is available below.

Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

Aanderaa Recording Current Meter Model 7/8

Manufacturer's specifications: recording unit height 49.5cm (RCM8 52.0cm), diameter 12.8cm, vane size 48.5x50.0cm. Meter is designed for depths down to 2000m (RCM8 6000m). It incorporates a spindle which is shackled to the mooring line. The meter is attached to the spindle through a gimbal mounting which permits a maximum 27° deviation of the spindle from the vertical, the meter still remaining horizontal.

Meter comprises :

1. Paddle wheel rotor magnetically coupled to an electronic counter

2. Vane, which aligns instrument with current flow, has a balance weight ensuring static balance and tail fins to ensure dynamic balance in flows up to 250cm/s.

3. Magnetic compass (needle is clamped to potentiometer ring) - direction recorded with 0.35° resolution, 5° accuracy for speeds 5 to 100cm/s, 7.5° accuracy for remaining speeds within 2.5 to 200cm/s range.

4. Quartz clock, accuracy better than 2 sec/day within temperature range 0 to 20°C.

5. Thermistor (temperature sensor), standard range -2.46 to 21.48°C (max on high range 36.04°C), accuracy 0.05°C, resolution 0.1 per cent of range, 63 per cent response time 12sec.

6. Inductive cell conductivity sensor (optional), range 0 to 70mmho/cm standard resolution 0.1 per cent of range.

7. Silicon piezoresistive bridge, standard range 0 to 3000 psi (RCM8 to 9000 psi), resolution 0.1% of range.

8. Self balancing potentiometer which converts the output from each sensor into a 10 bit binary number for storage on magnetic tape.

9. Associated electronics.

A built-in clock triggers the instrument at preset intervals and up to six channels are sampled in sequence. Channel 1 is a fixed reference reading for control purposes and data identification. Channels 2, 3 and 4 represent measurement of temperature, conductivity and pressure. Channels 5 and 6 represent the VECTOR AVERAGED current speed and direction since the previous triggering of the instrument. The number of rotor revolutions and the direction is sampled every 12 seconds and broken into North and East components. Successive components are added and recorded as speed and direction. For recording intervals longer than 10 minutes, speed and direction are sampled 1/50th of recording interval.

It has become common practice in some laboratories to deploy these meters as temperature and conductivity loggers without current measuring capabilities.

The following link will provide the manufacturer specifications:

Coastal Observatory Aanderaa Current Meter Data Processing

Data Originator's Processing

The following procedures are carried out before the data were supplied to BODC.

After the mooring was recovered, the data were downloaded from the instrument logger, and factory calibrations were applied to the temperature and conductivity channels. Where available, laboratory calibrations of the current direction channels were used; factory formulae were used in their absence. Where no form factor was known for the conductivity sensor, a value of 2.8 was used.

Before the data were supplied to BODC, basic quality control was performed by the Data Originator. The first stage of quality checks involved comparing the data from each instrument with CTD measurements recorded during the deployment and recovery of the mooring. Following the comparison against CTD data secondary checks were performed by comparing the data from each instrument against the data from other sensors attached to that mooring. The Originator has provided BODC with a document containing a full description of their quality control methodology. Depending on the result of the quality checks for each series, one of the following actions was performed by the Originator:

• The data were declared good quality and no corrections were applied.
• Series with consistent offsets, spikes or periods of bad data were edited to correct for these issues. Spikes and periods of unrealistic values were converted to absent data indicators.
• The series was marked as 'use with caution', if there were problems which the Originator was unable to correct, or it was unclear whether there was a problem with the data, such as in instances where it was not possible to perform all of the quality checks.
• If the quality of the data from a series was extremely poor, then the Originator recommended that the data should not be used.

A full description of the results of these quality checks can be found in the relevant Originator's data processing comments document.

Processing of Coastal Observatory Aanderaa RCM data by BODC

The data were provided to BODC in ASCII format, and the series were reformatted into BODC standard internal format using a transfer function. During this process, salinity was derived from the conductivity and temperature data, in accordance with the methods outlined in Foffonoff and Millard (1982). As no pressure channel was present, the pressure used in the derivation comprised a single nominal value calculated from the instrument depth provided in the header of the data file.

The table below shows how the variables within the processed data files were mapped to appropriate BODC parameter codes.

The reformatted data were visualised using the in-house EDSERPLO software. Suspect data were marked by adding an appropriate quality control flag, missing data by both setting the data to an appropriate value and setting the quality control flag. Any channels which comprised entirely of absent data indicators were excluded from the final qxf.

References

Fofonoff, NP and Millard, RC. 1983. Algorithms for computations of fundamental properties of seawater. UNESCO Technical Papers in Marine Science, 44, p.53.

General Data Screening carried out by BODC

BODC screen both the series header qualifying information and the parameter values in the data cycles themselves.

Header information is inspected for:

• Irregularities such as unfeasible values
• Inconsistencies between related information, for example:
  • Times for instrument deployment and for start/end of data series
  • Length of record and the number of data cycles/cycle interval
  • Parameters expected and the parameters actually present in the data cycles
• Originator's comments on meter/mooring performance and data quality

Documents are written by BODC highlighting irregularities which cannot be resolved.

Data cycles are inspected using time or depth series plots of all parameters. Currents are additionally inspected using vector scatter plots and time series plots of North and East velocity components. These presentations undergo intrinsic and extrinsic screening to detect infeasible values within the data cycles themselves and inconsistencies as seen when comparing characteristics of adjacent data sets displaced with respect to depth, position or time. Values suspected of being of non-oceanographic origin may be tagged with the BODC flag denoting suspect value; the data values will not be altered.

The following types of irregularity, each relying on visual detection in the plot, are amongst those which may be flagged as suspect:

• Spurious data at the start or end of the record.
• Obvious spikes occurring in periods free from meteorological disturbance.
• A sequence of constant values in consecutive data cycles.

If a large percentage of the data is affected by irregularities then a Problem Report will be written rather than flagging the individual suspect values. Problem Reports are also used to highlight irregularities seen in the graphical data presentations.

Inconsistencies between the characteristics of the data set and those of its neighbours are sought and, where necessary, documented. This covers inconsistencies such as the following:

• Maximum and minimum values of parameters (spikes excluded).
• The occurrence of meteorological events.

This intrinsic and extrinsic screening of the parameter values seeks to confirm the qualifying information and the source laboratory's comments on the series. In screening and collating information, every care is taken to ensure that errors of BODC making are not introduced.

Project Information

Proudman Oceanographic Laboratory Coastal Observatory

The Coastal Observatory was established by Proudman Oceanographic Laboratory as a coastal zone real time observing and monitoring system. The main objective is to understand a coastal sea's response both to natural forcing and to the consequences of human activity. Near real-time measurements will be integrated with coupled models into a pre-operational coastal prediction system whose results will be displayed on the World Wide Web.

The Observatory is expected to grow and evolve as resources and technology allow, all the while building up long time series. A site selection pilot study was carried out in September 2001 and the Observatory became operational in August 2002.

The site is located in Liverpool Bay and is subject to typical coastal sea processes, with strong tides, occasional large storm surges and waves, freshwater input, stable and unstable stratification, high suspended sediment concentration and biogeochemical interaction. Measurements and monitoring will focus on the impacts of storms, variations in river discharge (especially the Mersey), seasonality and blooms in Liverpool Bay.

A variety of methods will be used to obtain measurements, including:

1. Moored instruments for in situ time series of currents, temperature and salinity profiles, and surface waves and meteorology. It is hoped that turbidity and chlorophyll measurements will be made at another site as the Observatory progresses;
2. The Cefas Smartbuoy for surface properties such as nutrients and chlorophyll, starting late 2002;
3. R.V. Prince Madog to carry out spatial surveys and service moorings;
4. Instrumented ferries for near surface temperature, salinity, turbidity, chlorophyll and nutrients. The first route will be Liverpool to Douglas, Isle of Man, starting late 2002;
5. Drifters for surface currents and properties such as temperature and salinity, starting in 2004;
6. Tide gauges, with sensors for meteorology, waves, temperature and salinity, where appropriate;
7. Meteorological data from Bidston Observatory and Hilbre Island, HF radar and tide gauge sites;
8. Shore-based HF radar measuring waves and surface currents out to a range of 50 km, starting in 2003;
9. Satellite data, with infrared for sea surface temperature and visible for chlorophyll and suspended sediment.

The partners currently involved with the project are listed below:

• Proudman Oceanographic Laboratory
• British Oceanographic Data Centre
• UK Meteorological Office
• Centre for Environment, Fisheries and Aquaculture Science
• Environment Agency
• Liverpool University and Port Erin Marine Laboratory
• Bangor University School of Ocean Sciences
• National Oceanography Centre Southampton
• Department of Agriculture and Rural Development in Northern Ireland

A summary of Coastal Observatory cruises to date on R.V. Prince Madog is given in the table below:

Data Activity or Cruise Information

Data Activity

SmartBuoy deployment LB1_016/897

Deployment and recovery

This mooring was deployed in a collaboration between Cefas and the POL Liverpool Bay Coastal Observatory.

Rig Description

The Cefas SmartBuoy carried a suite of instruments mounted just below the surface, as well as instrumentation belonging to POL at 5 and 10 metres below the surface. Further information about the instrument suite is given in the table below.

The single point mooring was composed mainly of 0.5 inch long link chain, marked by a 1.8 m diameter toroid and anchored with a half tonne clump of scrap chain.

• Cefas - The Centre for Environment, Fisheries and Aquaculture Science, Lowestoft (UK)
• POL - The Proudman Oceanographic Laboratory, Liverpool (UK)

Related Data Activity activities are detailed in Appendix 1

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

Liverpool Bay Coastal Observatory Mooring Site A (COA/Site 1/Site 9)

This station is the main mooring site for the Proudman Oceanographic Laboratory (POL) Liverpool Bay Coastal Observatory and was first occupied in 2002. It is also known both as Coastal Observatory Site 1 and Site 9. POL perform two main types of activities at this station: they deploy moorings; and in addition, they take CTD profiles during each site visit. The station lies within a box of mean water depth 22.5 m with the following coordinates:

The position of this station relative to the other POL Coastal Observatory sites can be seen from the figure below.

Mooring Deployment History

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

2001

CTD Sampling History

The CTD instrument package for these cruises was a Sea-Bird 911plus, with beam transmissometer, fluorometer, LICOR PAR sensor, LISST-25, and oxygen sensor.

Key

AC-S = Absorption and attenuation spectrophotometer
ADCP = Acoustic Doppler Current Profiler
ADV = Acoustic Doppler Velocimeter
BD = Bacterial degradation experiment
BPR = Bottom Pressure Recorder
CT = Conductivity and temperature logger
CTD = Conductivity, temperature, depth sensor
FL = Fluorometer
NAS = in-situ nutrient analyser
OBS = Optical Backscatter Turbidity meter
OXY = Oxygen sensor
PAR = PAR sensor
T = Temperature logger
TR = Transmissometer
WMS = Automatic water sampler

Related Fixed Station activities are detailed in Appendix 2

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

Appendix 1: LB1_016/POLRIG897

Related series for this Data Activity are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.

Appendix 2: COA

Related series for this Fixed Station are presented in the table below. Further information can be found by following the appropriate links.

If you are interested in these series, please be aware we offer a multiple file download service. Should your credentials be insufficient for automatic download, the service also offers a referral to our Enquiries Officer who may be able to negotiate access.