Metadata Report for BODC Series Reference Number 541766


Metadata Summary

Data Description

Data Category Hydrography time series at depth
Instrument Type
NameCategories
SeaTech transmissometer  transmissometers
Aanderaa RCM 7/8 Recording Current Meter  current meters
Instrument Mounting fixed benthic node
Originating Country United Kingdom
Originator -
Originating Organization Proudman Oceanographic Laboratory (now National Oceanography Centre, Liverpool)
Processing Status banked
Project(s) Provess
 

Data Identifiers

Originator's Identifier as11814.820
BODC Series Reference 541766
 

Time Co-ordinates(UT)

Start Time (yyyy-mm-dd hh:mm) 1999-03-29 14:55
End Time (yyyy-mm-dd hh:mm) 1999-05-19 07:35
Nominal Cycle Interval 600.0 seconds
 

Spatial Co-ordinates

Latitude 52.30630 N ( 52° 18.4' N )
Longitude 4.30020 E ( 4° 18.0' E )
Positional Uncertainty 0.1 to 0.5 n.miles
Minimum Sensor Depth 18.5 m
Maximum Sensor Depth 18.5 m
Minimum Sensor Height 1.5 m
Maximum Sensor Height 1.5 m
Sea Floor Depth 20.0 m
Sensor Distribution Sensor fixed, measurements made at fixed depths - The sensor is at a fixed depth, but measurements are made remotely from the sensor over a range of depths (e.g. ADCP measurements)
Sensor Depth Datum Sea floor reference - Depth measured as a height above sea floor but converted into a depth relative to the sea surface according to the same datum as used for sea floor depth (applicable to instrument depths not bathymetric depths)
Sea Floor Depth Datum Instantaneous - Depth measured below water line or instantaneous water body surface
 

Parameters

BODC CODE Rank Units Short Title Title
AADYAA01 1 Days Date(Loch_Day) Date (time from 00:00 01/01/1760 to 00:00 UT on day)
AAFDZZ01 1 Days Time(Day_Fract) Time (time between 00:00 UT and timestamp)
ATTNMR01 1 per metre Atten_red Attenuation (red light wavelength) per unit length of the water body by 20 or 25cm path length transmissometer
CNDCPR01 1 Siemens per metre InSituCond Electrical conductivity of the water body by in-situ conductivity cell
PREXPS01 1 Decibars MeasPress_SL Pressure (measured variable) exerted by the water body by fixed in-situ pressure sensor and corrected to read zero at sea level
PSALPR01 1 Dimensionless P_sal Practical salinity of the water body by conductivity cell and computation using UNESCO 1983 algorithm
TEMPPR01 1 Degrees Celsius Temp Temperature of the water body
 

Definition of Rank

  • Rank 1 is a one-dimensional parameter
  • Rank 2 is a two-dimensional parameter
  • Rank 0 is a one-dimensional parameter describing the second dimension of a two-dimensional parameter (e.g. bin depths for moored ADCP data)

Problem Reports

No current speed or direction are available for this instrument.

The instrument's recorded pressure indicated a depth deeper than the total water depth measured on deployment by the ship's echo-sounder by at least 10 metres. Absolute pressure values from this instrument should therefore be used with caution.

The attenuance time-series shows that the transmissometer saturated at 9.9 per metre. Records reaching this value were flagged '>'.

Towards the end of the record from 1 May 1999 03:00, the attenuance signal indicated a final 'event' which was identified as suspect by the data originators (SPM group, UNW, Bangor) and which was probably due to the battery getting flat. Records from 1 May 1999 03:00 have therefore been flagged as suspect.

The data originators also highlighted that a few attenuance values were below 0.364 per metre which is the typical value for particle free water at 660 nm in these instruments. The minimum value for data points not flagged as suspect was 0.22 per m. Although these low values were isolated and of small magnitude, they could suggest that the transmissometer reading of beam attenuation was underestimating the real value. Absolute attenuance value from this instrument should therefore be used with caution.

Throughout the record, the salinity and conductivity values appear low (by ca. 0.5 PSU for salinity) relative to concomitant conductivity/salinity measurements obtained from other instruments deployed close to this instrument position and depth.

Absolute salinity values from this instrument should therefore be used with caution.


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:

Manufacturer specifications

SeaTech Transmissometer

Introduction

The transmissometer is designed to accurately measure the the amount of light transmitted by a modulated Light Emitting Diode (LED) through a fixed-length in-situ water column to a synchronous detector.

Specifications

Notes

The instrument can be interfaced to Aanderaa RCM7 current meters. This is achieved by fitting the transmissometer in a slot cut into a customized RCM4-type vane.

A red LED (660 nm) is used for general applications looking at water column sediment load. However, green or blue LEDs can be fitted for specilised optics applications. The light source used is identified by the BODC parameter code.

Further details can be found in the manufacturer's Manual .

Aanderaa Current Meter Data Processing

Data Originator's Processing

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

Data were downloaded from the instrument logger, and factory calibrations were applied to the current speed channel, and the pressure, conductivity and temperature channels when fitted. 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.

Please note (concerns vector averaged current data): The current data are averaged by the logger over the sampling interval, whereas the pressure, temperature and conductivity data are single point measurements taken at the end of the interval. The data originator has moved the time stamps to the mid-point of the vector averaging sampling interval for all channels without interpolation.

BODC Data Processing and Quality Control

Where pressure sensors were fitted: the data record was compared with the pressure computed from the water depth on deployment and rig geometry. The time series was visually screened for evidence of rig movement (e.g. trawling) and excessive leaning (perhaps due to strong currents).

Where temperature sensors were fitted: the data record was compared with calibrated CTD data taken in the vicinity and checked for agreement within a few tenths of a degree Celsius. Obvious spikes were flagged. Periods of excessively noisy data were noted.

Where conductivity sensors were fitted: salinity (PSS-78) was computed from in-situ temperature and conductivity and a nominal pressure computed from the water depth on deployment and rig geometry. Obvious spikes were flagged.

Data Processing Notes

Transmissometer Calibration (University of Wales, Bangor, UK)

Transmission readings from the SeaTech transmissometer interfaced with the Aanderaa current meter SN11814 were converted to attenuance using the following values:

Air correction reading = 653
Blanked path reading = 0

These values were determined following a pre-deployment in situ calibration cast when the two SeaTech transmissometers to be used during the PROVESS SNS mooring experiment were strapped to the CTD frame during Pelagia PE136 cruise (CTD001). The CTD was then lowered to the bed, brought back close to the surface and held at this depth for 5 minutes (see BODC documentation 66467 for further details on calibration procedure).

SeaTech Transmissometer Data Processing

Deployment/Recovery Procedure

(A. Banaszek/ P.Knight, Proudman Oceanographic Laboratory, Birkenhead)

Prior to deployment, the counts logged by the transmissometer in free air and with the light path blocked were recorded. It was then strapped to the CTD frame, lowered into the water and held at a fixed depth for approximately 20 minutes for intercalibration with the CTD transmissometer.

On recovery the data were downloaded from the instrument logger and supplied to BODC as raw counts.

Post-Cruise Calibration

(Dr. S.E. Jones, University of Wales, Bangor)

The raw transmission counts were compared with fully corrected CTD attenuance data from the intercalibration cast. The air-correction counts reading (ACR) for each deployment was found from inversion of the formula:

Atten = -(1/p) * ln { (counts-BPR) / (ACR - BPR) }

where:

Atten = CTD attenuance (per metre)
p = path length (metres)
counts = datalogger reading (counts)
BPR = blocked path reading (counts)
ACR = air correcion reading (counts)

Air correction reading values for each instrument deployment were passed on to BODC.

BODC Data Processing and Quality Control

The data were then converted from data logger counts to attenuance (per metre) by applying the above calibration formula to each datacycle in the series.

The data were visually screened for evidence of fouling on the optics, leaking power connectors and flat batteries. Obvious spikes and any features believed to be of non-oceanographic origin were flagged suspect.

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:

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:

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:

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

PROcesses of Vertical Exchange in Shelf Seas (PROVESS)

Introduction

PROVESS was an interdisciplinary study of the vertical fluxes of properties through the water column and the surface and bottom boundary layers. The project was funded by the European Community MAST-III programme (MAS3-CT97- 0159) and ran from March 1998 to May 2001.

Scientific Rationale

PROVESS was based on the integration of experimental, theoretical and modelling studies with the aim of improving understanding and quantification of vertical exchange processes in the water column, in particular in the surface and benthic boundary layers and across the> pycnocline. PROVESS also explored mechanisms of physical-biological coupling in which vertical exchanges and turbulence significantly affect the environmental conditions experienced by the biota with particular reference to aggregation, flocculation, sedimentation and trophic interactions.

Fieldwork

The experimental phase of the project was carried out at two contrasting sites in the North Sea: the northern North Sea site (NNS) and the southern North Sea site (SNS).

The two sites had the following characteristics:

SNS NNS
Position 52° 15.0' N, 4° 17.0' E 59° 20.0' E, 1° 00.0' E
Time of year April-May September-November
Water depth (m) 16 100
M2 max amplitude (m s-1) 0.75 0.15
Max current (m s-1) 1.0 0.6
Delta T (deg C) mixed 7-1
Thermocline depth (m) mixed 35-100
Delta S 1 small
Halocline depth (m) 5-10 cf. thermocline depth
Max wind speed (m s-1) 20 25
Max wave height (m) 5 10
Max wave period (s) 8 10
Internal motion No Yes
Sediment muddy-sand muddy-sand
Biology eutrophic oligotrophic

At both locations measurements were concentrated at a central position with additional measurements being made to estimate horizontal gradients. Moored instruments (including current meters, temperature and pressure sensors, fluorometers, transmissometers, nutrient analysers and meteorological sensors) were deployed between 7 September and 5 November 1998 at the NNS and between 29 March and 25 May 1999 at the SNS. Each experiment was supported by intensive measurement series made from oceanographic ships and involving turbulence dissipation profiler CTD, particle size profilers, optical profilers, benthic sampling and water bottle sampling.

Details of the cruises were as follows:

Site Ship
(nationality)
Cruise
Mnemonic
Date
NNS Valdivia (GER) VA174 5 - 17 Sep 1998
  Dana (DK) D1198 14 - 26 Oct 1998
  Pelagia (NL) PE125 19 - 30 Oct 1998
  Challenger (UK) CH140 22 Oct - 9 Nov 1998
SNS Pelagia (NL) PE135 29 Mar - 9 Apr 1999
  Mitra (NL) MT0499 19 - 30 Apr 1999
  Belgica (BE) BG9912 17 - 21 May 1999

Data Activity or Cruise Information

Data Activity

Start Date (yyyy-mm-dd) 1999-03-29
End Date (yyyy-mm-dd) 1999-05-19
Organization Undertaking ActivityProudman Oceanographic Laboratory (now National Oceanography Centre, Liverpool)
Country of OrganizationUnited Kingdom
Originator's Data Activity IdentifierPOLRIG#820
Platform Categoryfixed benthic node

PROVESS Project POLRIG#820

This mooring was known within PROVESS as either 'Rig A' or the STABLE mooring. It was one of a cluster of moorings deployed at the main focus of the Southern North Sea Site during the spring of 1999. The rig was deployed by RV Pelagia (cruise PE136) in March 1999 and recovered by RV Belgica (cruise BG9912) in May 1999.

Mooring type U-shaped mooring with spar buoy and STABLE bottom frame.
Instruments mounted on STABLE
(1.5 m above the sea-bed)
Electromagnetic current meter
Savonius rotor current meter
STD-12 Plus #692
Aanderaa current meter fitted with SeaTech transmissometer (S/N 11814)

Notes:

Other Series linked to this Data Activity - 541871

Cruise

Cruise Name PE136
Departure Date 1999-03-29
Arrival Date 1999-04-09
Principal Scientist(s)Hans van Haren (Royal Netherlands Institute for Sea Research)
Ship RV Pelagia

Complete Cruise Metadata Report is available here


Fixed Station Information

Fixed Station Information

Station NamePROVESS Southern North Sea Site
CategoryOffshore area
Latitude52° 18.00' N
Longitude4° 18.00' E
Water depth below MSL16.0 m

PROVESS Southern North Sea Site

Eleven mooring packages were deployed at PROVESS Southern North Sea site by Pelagia cruise PE136 in March 1999. One of these (Rig U) was lost, the NIOZ mooring was recovered by PE136 in April 1999 and the remaining nine were recovered by either RV Belgica cruise BG9912 (8 moorings) or RV Zirfea (Rig V) in May 1999.

The layout of the mooring array was:

BODC image

The asterisk represents an array of five moorings as detailed in the inset map.

Mooring data

The data returned from each rig were as follows:

Rig identifier Data
A POLRIG#820 Near-bed currents
Temperature, salinity and attenuance
B POLRIG#821 ADCP currents
Water level
Thermistor plus conductivity chain
D POLRIG#822 Currents
H POLRIG#824 Currents
Nutrients (nitrate + nitrite, silicate)
Chlorophyll
G POLRIG#823 Surface attenuance, nutrients (nitrate + nitrite) and chlorophyll
NIOZ   ADCP currents
Thermistor chain
Wave statistics (considered suspect)
V POLRIG#827 Currents
Temperature (4 depths)
Y POLRIG#829 Water level
Near-bed temperature
T POLRIG#825 ADCP currents
Water level
Thermistor plus conductivity chain
U Unknown None
X POLRIG#828 Water level
Near-bed temperature

CTD data

A total of 356 CTD casts were also collected during the three cruises surveying this area. These include:

Cruise identifier Cruise dates No. of CTD casts
RV Pelagia (#136) 29 March - 09 April 1999 133
Mitra (#0499) 19 April - 30 April 1999 170
RV Belgica (#9912) 17 May - 21 May 1999 53

Additonal data

Supporting meteorological data (including sea surface temperature and wave statistics) from two platforms (52° 33' N, 4° 3.5' E and 52° 16.4' N, 4° 17.8' E) were supplied to the project and are held by BODC. These series run from the beginning of March 1999 until the end of May 1999.

Other Series linked to this Fixed Station for this cruise - 529245 529257 529269 529270 529282 529294 529301 529313 529325 529337 529349 529350 541730 541742 541754 541778 541791 541809 541810 541822 541834 541846 541858 541871 541895 541902 541926 541938 553141 553294 553301 553313 564243


BODC Quality Control Flags

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

Flag Description
Blank Unqualified
< Below detection limit
> In excess of quoted value
A Taxonomic flag for affinis (aff.)
B Beginning of CTD Down/Up Cast
C Taxonomic flag for confer (cf.)
D Thermometric depth
E End of CTD Down/Up Cast
G Non-taxonomic biological characteristic uncertainty
H Extrapolated value
I Taxonomic flag for single species (sp.)
K Improbable value - unknown quality control source
L Improbable value - originator's quality control
M Improbable value - BODC quality control
N Null value
O Improbable value - user quality control
P Trace/calm
Q Indeterminate
R Replacement value
S Estimated value
T Interpolated value
U Uncalibrated
W Control value
X Excessive difference

SeaDataNet Quality Control Flags

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

Flag Description
0 no quality control
1 good value
2 probably good value
3 probably bad value
4 bad value
5 changed value
6 value below detection
7 value in excess
8 interpolated value
9 missing value
A value phenomenon uncertain