Ruth Lawless, August 2001
Comments or queries can be emailed to the Program Manager, currently Jon Reeve, at firstname.lastname@example.org
1. Underway Data Start Time: 24 October 1992 04:04 UTC
Underway Data End Time: 23 November 1992 05:19 UTC
3. Logging System: ALF and NOQALMS
17 October Hobart 02 - 05 November Mawson 07 - 09 November Marine Science 10 - 12 November Davis 23 November Hobart
4. Data Sampling Interval: 60 seconds
5. Data Gaps
* No data were logged prior to 24 October 04:04 UTC.
* There are no FLU_FLOW or Water Depth (bathymetry) data prior to 07 November 13:24 UTC.
* There are no FLU_VALUE or Ship's Heading data loaded.
* All parameters are affected by a data gap between:
7. Data Quality of Checked Parameters
ALF data existing on the marine database from this voyage were found to be incomplete and were replaced with the more comprehensive NOQALMS dataset in August 2001. However, NOQALMS data logged from the fluorometer have not been located, so FLU_FLOW data remains that sourced from ALF files.
The following is a description of what criteria were used to flag data as "good" or "bad". Even if users rely on their own data quality checking, it is recommended that they refer to this section as some parameters (e.g. air temperature) may be affected by others (e.g. apparent wind direction). Underway data users should also refer to Section 5 on Data Gaps.
There is no documentation on the processing protocol used or the quality of these data.
Course over Ground (GPS_COG)
GPS_COG measures the direction of the movement of the ship.
GPS_COG data are sometimes scattered when GPS_SOG is low, but these were left as good as this relationship is not consistent. Data between 11 November 22:55 UTC and 13 November 01:11 UTC were rejected (remain at a constant value), as were occasional outliers.
Ship's Speed (SS) and Speed over Ground (GPS_SOG)
SS is derived from the electromagnetic current meter and is directly affected by waves. SS is a measurement of the ship's speed through the water, while GPS_SOG is a measurement of ship's speed relative to the ground.
Although trends in SS and GPS_SOG are similar, SS values are about half those of GPS_SOG in magnitude and were therefore all rejected. GPS_SOG data between 11 November 22:55 UTC and 13 November 01:11 UTC were flagged bad (remain at a constant value), as were occasional outliers.
Fluorometer Flow (FLU_FLOW)
Apart from a section on 19 November where values remain constant and don't resemble real data, FLU_FLOW were all accepted as good.
Thermosalinograph Parameters: Salinity (TSG_SALIN), Temperature
(TSG_TEMP), Conductivity (TSG_CNDUCT)
Outputs for these parameters do not resemble real data and were therefore all rejected.
Water Temperature - low resolution (W_TEMP) and Water Temperature
- high resolution (W_TEMP_HI)
This is the first voyage that the high resolution water temperature sensor was used. It was installed because the accuracy of the low resolution sensor was compromised when in pack-ice (subject to freezing) or during heavy pitching (would take in air). Indeed, although trends in data from the two sensors are similar, values differ significantly and all W_TEMP data were flagged bad.
Accuracy of W_TEMP_HI data relies on flow through the uncontaminated seawater line. Therefore, W_TEMP_HI data were rejected where FLU_FLOW is low, bad or absent. Scattered data were also marked bad.
Air Temperature Port and Starboard (A_TEMP_P and A_TEMP_S)
Warm exhaust air from the funnel on the monkey aisle, which is aft of the air temperature sensors, can corrupt the air temperature data. When apparent wind direction is between 120-170º, air temperature readings from the port sensor are higher than those from the starboard sensor and were rejected. Similarly, when the starboard sensor is downwind of the funnel (i.e. when apparent wind direction is between 190-240º), air temperature readings are high relative to those from the port sensor and were flagged as bad.
Erratic air temperature traces related to erratic apparent wind direction data were marked bad. Data from one sensor were also marked bad if much more erratic than that from the other sensor. Scattered data and outliers were rejected.
Barometric Pressure (BAR)
BAR values do not resemble real data and were all flagged bad.
Humidity Port and Starboard (HUMID_P and HUMID_S)
The humidity sensors are located close to the air temperature sensors and are therefore also affected by exhaust air from the funnel, although to a lesser extent. Data from the downwind sensor may be decreased compared to the unaffected sensor. Consequently, humidity data were quality checked with respect to apparent wind direction data using the same criteria as for air temperature data.
Values greater than 100% were flagged bad, as were outliers. Scattered data related to erratic wind direction data were also marked bad. Good data from the port and starboard humidity sensors are generally within 5 - 10% of each other.
Photosynthetically Active Radiation (LICOR_R)
Note that this sensor is affected at different times by shadows e.g. from the ship's superstructure.
LICOR_R values less than zero or greater than 2000 µmol/sec/m2 were marked bad. Some night-time values are slightly > zero, but these were left as good.
Wind Direction Apparent Port (WDPA) and Wind Direction True Port
Wind Speed Apparent Port (WSPA) and Wind Speed True Port (WSPT)
According to the Computer Logbook, the anemometer blades were damaged on 13 November. All wind speed and direction data were therefore rejected after 13 November 00:00 UTC.
All other WDPA, WDPT and WSPA data were left as good.
True Wind Speed data are partly derived from Ship's Heading data. As
SS data for this voyage are inaccurate, all WSPT data were flagged bad.