Metadata Report for BODC Series Reference Number 1223127

• 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

Quality Control Report

The light channel values appear large for the latitude and time of year, and there is a large offset (maximum difference approximately 300 W m^-2) between the set of TIR channels, therefore these were not merged. The offset is smaller (maximum difference approximately 30 W m^-2) between the PAR channels, therefore, these have been merged into one maximum channel. There were negative values in all light channels after the manufacturer's calibration had been applied, and so the effected cycles have been flagged as improbable.

There were several issues relating to the wind data including changes in the orientation of the anemometer and problems with the sensor not recording accurate speeds and directions when the wind was coming from the stern as described in the originator's data processing section. The change in anemometer orientation has been corrected for and those values which have likely been affected by the underestimation of wind speed and direction have been flagged.

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

DIMES James Cook Cruise JC069 Meteorology Instrumentation

The following table shows the meteorological sensors used on board the ship, located above the ship's bridge, 17.1 m above sea level on the met platform.

Gill Instruments Windsonic Anemometer

The Gill Windsonic is a 2-axis ultrasonic wind sensor that monitors wind speed and direction using four transducers. The time taken for an ultrasonic pulse to travel from the North to the South transducers is measured and compared with the time for a pulse to travel from South to North. Travel times between the East and West transducers are similarly compared. The wind speed and direction are calculated from the differences in the times of flight along each axis. This calculation is independent of environmental factors such as temperature.

Specifications

Further details can be found in the manufacturer's specification sheet.

Kipp and Zonen Pyranometer Model CM6B

The CM6B pyranometer is intended for routine global solar radiation measurement research on a level surface. The CM6B features a sixty-four thermocouple junction (series connected) sensing element. The sensing element is coated with a highly stable carbon based non-organic coating, which delivers excellent spectral absorption and long term stability characteristics. The sensing element is housed under two concentric fitting Schott K5 glass domes.

Specifications

Skye Instruments PAR Energy Sensor Model SKE 510

The SKE 510 is suitable for measuring photosynthetically active radiation (PAR) from natural or artificial light sources. The sensor is fully waterproof and guaranteed submersible to 4m depth, and indoor versions are also available.

The instrument uses a blue-enhanced planar diffused silicon detector to measure energy (in W m^-2) over the 400-700 nm waveband. It has a cosine-corrected head and a square spectral response. The sensor can operate over a temperature range of -35 to 70 °C and a humidity range of 0-100% RH.

Specifications

Vaisala Analog Barometers Models PTB100 (A), (B) and PTB101 (B), (C)

The PTB 100 series analog barometers are designed both for accurate barometric measurements at room temperature and for general environmental pressure monitoring over a wide temperature range. The long-term stability of the barometer minimizes the need for field adjustment in many applications.

Physical Specifications

The barometers use the BAROCAP^* silicon capacitive absolute pressure sensor developed by Vaisala for barometric pressure measurements. The BAROCAP^* sensor combines the elasticity characteristics and mechanical stability of a single-crystal silicon with the proven capacitive detection principle.

Sensor Specifications

^* BAROCAP is a registered trademark of Vaisala

Vaisala Temperature and Relative Humidity HMP Sensors

A family of sensors and instruments (sensors plus integral displays or loggers) for the measurement of air temperature and relative humidity. All are based on a probe containing a patent (HUMICAP) capacitive thin polymer film capacitanece humidity sensor and a Pt100 platinum resistance thermometer. The probes are available with a wide range of packaging, cabling and interface options all of which have designations of the form HMPnn or HMPnnn such as HMP45 and HMP230. Vaisala sensors are incorporated into weather stations and marketed by Campbell Scientific.

All versions operate at up to 100% humidity. Operating temperature ranges vary between models, allowing users to select the version best suited to their requirements.

Further details can be found in the manufacturer's specification sheets for the HMP 45 series, HMP 70 series and HMP 230 series.

Trimble Applanix Position and Orientation Systems for Marine Vessels (POSMV)

The Position and Orientation Systems for Marine Vessels (POSMV) is a real time kinematic (RTK) and differential global positioning system (DGPS) receiver for marine navigation. It includes an inertial system that provides platform attitude information. The instrument provides accurate location, heading, velocity, attitude, heave, acceleration and angular rate measurements.

There are three models of Applanix POSMV, the POS MV 320, POS MV Elite and the POS MV WaveMaster. POS MV 320 and POS MV WaveMaster are designed for use with multibeam sonar systems, enabling adherence to IHO (International Hydrographic Survey) standards on sonar swath widths of greater than ± 75 degrees under all dynamic conditions. The POS MV Elite offers true heading accuracy without the need for dual GPS installation and has the highest degree of accuracy in motion measurement for marine applications.

Specifications

POS MV 320

POS MV WaveMaster

POS MV Elite

¹ One Sigma, depending on quality of differential corrections
² Whichever is greater, for periods of 20 seconds or less

Further details can be found in the manufacturer's specification sheet.

Data Processing Procedures

Originator's Data Processing

Data were logged daily by the onboard logging system (TECHSAS). Surfmet data were transferred from the TECHSAS system and reformatted into Mstar format NetCDF using NOC-generated Mstar processing scripts on a daily basis.

Ship speed, position and heading from the bestnav file were merged onto the wind data in the surfmet file and wind speed units were corrected from knots to m s^-1. The absolute wind speed and direction were then calculated and vector averaged. In order to avoid ambiguity, variable units are explicit in whether wind directions are 'towards' or 'from' the direction in question.

There was found to be a problem with wind direction near the 0°/360° boundary during the cruise. As the anemometer was set up with 0°/360° at the bow, the relative wind was very often around this heading. The anemometer data were recorded at the data rate generated by the sensor (nominal 1 Hz), however, there was still a problem with the raw data, in particular, when the wind was near 0°/360°, as the TECHSAS files sometimes contained headings in between (e.g. in the range 150° to 210°) and when these were used in the correct calculation of true wind, this resulted in bad data. Therefore, the sensor was physically rotated 90° to port so that the 0°/360° boundary was athwartships, and a 90° offset was applied to the data, putting relative directions in the range -90° to 270°. The real time surfmet display could not correctly interpret the negative headings however, and displayed all winds in the port-forward sector as zero relative heading. The data in the TECHSAS files appeared fine, but there was confusion caused by the displays and it was not possible to update the surfmet software during the cruise. The sensor was therefore rotated back to its original position. The data with the rotated sensor occur between 11 February 2012 to 15 February 2012.

Downwelling PAR and TIR data were ingested and stored, but no further processing was undertaken.

At the end of the cruise, bad atmospheric pressure data were noticed and removed.

The following files were submitted to BODC:

BODC Data Processing

Three Mstar files were used to provide all of the meteorological data and were reformatted to the internal QXF format via the nearest neighbour method. The light channels were provided in units of x10^-5 volts, therefore these were converted back to raw voltages (/10⁵).

The relative wind direction provided by the originator had not been corrected for the change in anemometer orientation between 11 February 2012 11:18:00 hours and 15 February 2012 11:07:00 hours, during this time period values ranged from -86.782° to 359.921°. In order to correct for this, the 90° was added to these directions. In addition, the absolute wind direction calculated by the originator's did not account for the change in the anemometer direction, therefore, absolute wind direction and wind speed where calculated using the updated relative wind direction, relative wind speed, BODC derived velocity channels and the ship's heading using BODC established procedures.

All reformatted and calibrated data were visualised using the in-house Edserplo software. Suspect data were marked by adding the appropriate quality control flag. All light values below 0 were flagged as being improbable. Following advice from the originator who found that the anemometer underestimated the wind when it was coming from the stern, the relative wind directions between 160° and 200° were flagged as improbable, as well as the corresponding relative wind speed and absolute wind direction and speed.

Data were provided when the ship was still in port, therefore, the file was trimmed at the beginning to match the cruise start date.

The following tables show how the variables within the files were mapped to appropriate BODC parameter codes:

Met light Mstar file

Met Mstar file

Met averaged Mstar file

Calibrations

The voltages from the TIR and PAR channels were calibrated from volts to W m^-2 using the manufacturer's calibration sheets.

PTIR was calibrated using: CVLTRP01 = output volts * (1/10.90 x10^-6)
STIR was calibrated using: CVLTRS01 = output volts * (1/9.70 x10^-6)
PPAR was calibrated using: DVLTRPSD = output volts * (1/10.15 x10^-6)
SPAR was calibrated using: DWIRRSSD = output volts * (1/10.65 x10^-6)

As there appeared to be no large offset between the two sets of PAR sensors, the port and starboard sensors were combined by taking the greater value of these in order to eliminate shading effect. There appeared to be a large offset between the two sets of TIR sensors therefore these were not merged.

Project Information

Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) project document

DIMES is a US/UK field program aimed at measuring diapycnal and isopycnal mixing in the Southern Ocean, along the tilting isopycnals of the Antarctic Circumpolar Current.

The Meridional Overturning Circulation (MOC) of the ocean is a critical regulator of the Earth's climate processes. Climate models are highly sensitive to the representation of mixing processes in the southern limb of the MOC, within the Southern Ocean, although the lack of extensive in situ observations of Southern Ocean mixing processes has made evaluation of mixing somewhat difficult. Theories and models of the Southern Ocean circulation have been built on the premise of adiabatic flow in the ocean interior, with diabatic processes confined to the upper-ocean mixed layer. Interior diapycnal mixing has often been assumed to be small, but a few recent studies have suggested that diapycnal mixing might be large in some locations, particularly over rough bathymetry. Depending on its extent, this interior diapycnal mixing could significantly affect the overall energetics and property balances for the Southern Ocean and in turn for the global ocean. The goals of DIMES are to obtain measurements that will help us quantify both along-isopycnal eddy-driven mixing and cross-isopycnal interior mixing.

DIMES includes tracer release, isopycnal following RAFOS floats, microstructure measurements, shearmeter floats, EM-APEX floats, a mooring array in Drake Passage, hydrographic observations, inverse modeling, and analysis of altimetry and numerical model output.

DIMES is sponsored by the National Science Foundation (U.S.), Natural Environment Research Council (U.K) and British Antarctic Survey (U.K.)

For more information please see the official project website at DIMES

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

Fixed Station Information

World Ocean Circulation Experiment (WOCE) Southern Repeat Section 1 - South America to West Antarctic Peninsula

WOCE established a repeat hydrographic section across Drake Passage and designated it SR1 (also known as A21). The section is located between the Southern tip of South America and the West Antarctic Peninsula within a bounding box of 55° 19.40' S, 68° 15.80' W (North-Western corner) and 64° 8.52' S, 63° 4.80' W (South-Eastern corner).

A table of cruises which occupied SR1 is presented below with links to the relevant cruise reports (where available).

Related Fixed Station activities are detailed in Appendix 1

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: Drake Passage - WOCE SR1

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.