The data referenced in this report were collected from the research
vessel Aurora Australis (call sign: UNAA; contact: S. Rintoul) Data Logging
System from each of 4 different cruises for WOCE. The original data were
converted to a standard format and then preprocessed using an automated
data checking program. A visual inspection was then completed by a data
quality evaluator (DQE) who reviewed, modified, and added appropriate quality
control flags to the data. Details of the WOCE QC can be found in Smith
et al. (1996). This report summarizes flags for the Aurora Australis data
including flags added by both the preprocessor and the DQE.
The data from the Aurora Australis were expected to in include observations every 15 minutes from 4 covering 11 hydrographic sections. The Cruise Track Code (CTC), the begin and end dates, the number of records, values, and flags, and the percentage of non-Z flags for each cruise are given in table 1.
CTC | Dates | Number of Records | Number of Values | Number of Flags | Percent Flagged |
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Time (TIME), latitude (LAT), longitude (LON), platform heading (PL_HD), platform speed (PL_SPD), earth relative wind direction (DIR), earth relative wind speed (SPD), sea temperature (TS), atmospheric pressure (P), port dry-air temperature (T), starboard dry-air temperature (T2), port relative humidity (RH), and starboard relative humidity (RH2) were quality controlled. A total of 265265 values were checked, and 4415 flags were added resulting in 1.66 percent of the data being flagged. Table 2 summarizes the flag distribution including percentages flagged for each variable sorted by type.
Variable | Data out of Bounds | Unreal Movement | 4 S.D. from Climatology | Interesting Data | Spike in Data | Total Number of Flags | Percentage of Variables Flagged |
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Due to the high southern latitude of the vessel, interesting features occurred throughout this data set. Compared with their relative climatological mean, atmospheric pressure and air temperature were exceptionally low, and wind speed was extremely high for all the cruises. This was signified by the numerous "G", data >4 s.d. from climatological mean, and "B", data out of bounds, flags for those variables. These extreme conditions are not unexpected, however, as most of the observations were taken between Tasmania and the Antarctic coastline. This region, often called the roaring forties, is well known for strong cyclones, high winds, and hazardous navigation.
For the entire data set, the lowest atmospheric pressure was 932.5 mb at 15:07on 8/25/95 during cruise SR_03_/05. The highest wind speed was 31 m/s at 20:07 on 2/22/94 during cruise SR_03_/03. These, plus any other significantly low pressures or high wind speeds were flagged with an "I".
The only problem with the data set is that a significant portion of the data are missing. This is probably due to instrument failure after the system had been exposed to the extreme conditions detailed above for extended periods of time. Under the DAC QC system, missing data values are valid and are flagged with a "Z", good data. This may bias statistics for these files. Table 3 summarizes missing data information for each file.
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These data were in excellent condition. The user should be wary of using
UNAA.940226004v100.nc as over 60% of the data is missing. It is the analysts
opinion that even with the missing data, no problems should occur with
its use.
Smith, S.R., C. Harvey, and D.M. Legler, 1996: Handbook of Quality Control
Procedures and Methods for Surface Meteorology Data. WOCE Report
No. 141/96, Report WOCEMET 96-1, Center for Ocean Atmospheric Prediction
Studies, Florida State University, Tallahassee, FL 32310.