Aurora Australis Data Quality Control Report


Cruises: SR_03_/02
                 SR_03_/03
                 S__04_/04
                 SR_03_/05

Daniel M. Gilmore and Shawn Smith

World Ocean Circulation Experiment(WOCE)

Surface Meteorological Data Assembly Center(DAC)
Center for Ocean-Atmospheric Prediction Studies(COAPS)
The Florida State University

June 18, 1996

Report WOCEMET 96-6
Version 1.0


Introduction;
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.



Statistical Information:
The data from the Aurora Australis were expected to in include observations every 15 minutes from 4 cruises. 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.

Table 1: Record Data for Aurora Australis WOCE Cruises

CTC Dates Number of Records Number of Values Number of Flags Percent Flagged
SR_03_/02
03/11/93 - 05/02/93
5562
72306
1383
1.91
SR_03_/03
01/01/94 - 03/02/94
5573
72449
394
0.54
S__04_/04
12/13/94 - 02/02/95
4828
62764
88
0.14
SR_03_/05
07/12/95 - 09/03/95
4442
57746
2550
4.42

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.



Table 2: Frequency of Flags Assigned for each variable
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
TIME
            
0.00
LAT
  
1
      
1
0.00
LON
  
1
      
1
0.00
PL_HD
            
0.00
PL_SPD
            
0.00
DIR
        
1
1
0.00
SPD
    
534
5
  
539
2.64
TS
    
442
  
8
450
2.21
P
94
  
887
14
1
996
4.88
T
    
1141
    
1141
5.59
T2
    
1047
    
1047
5.13
RH
    
108
    
108
0.53
RH2
    
131
    
131
0.64
Totals:
94
2
4290
19
10
4415
1.66
Percentage of Flags Used
0.04
0.001
1.62
0.01
0.004
1.66
  


Summary:
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.

Table 3: Summary of Missing Data for Analyzed Variables
File
Number of Values
Number of Missing Values
Percent of Data Missing
UNAA.930311014v100.nc
13120
1097
8.36
UNAA.930325010v100.nc
8890
1671
18.80
UNAA.930402008v100.nc
6730
2815
41.83
UNAA.930404014v100.nc
13440
1613
12.01
UNAA.930418014v100.nc
13440
1176
8.75
UNAA.940101014v100.nc
13110
1510
11.52
UNAA.940115014v100.nc
13440
261
1.94
UNAA.940129014v100.nc
13360
684
5.12
UNAA.940212014v100.nc
12900
999
7.74
UNAA.940226004v100.nc
2920
2039
69.83
UNAA.941213014v100.nc
13180
4168
31.62
UNAA.941227014v100.nc
13430
2979
22.18
UNAA.950110014v100.nc
13350
3462
25.93
UNAA.950124009v100.nc
8320
3541
42.56
UNAA.950712014v100.nc
12780
2880
22.54
UNAA.950731014v100.nc
13330
2436
18.27
UNAA.950814014v100.nc
13440
0
0.00
UNAA.950828006v100.nc
4870
1
0.02



Final Note:
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.



References:
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.