Vidal Gormaz Bridge Data Quality Control Report

 

 

 

 

Jennifer Lovell and Shawn R. Smith

 

 

 

World Ocean Circulation Experiment

 

 

WOCE Surface Meteorological Data Analysis Center

Center for Ocean Atmospheric Prediction Studies

Florida State University

 

June 1, 2001

Report WOCEMET 01-09

Version 1.0


 



 

INTRODUCTION

This report summarizes the quality of surface meteorological data collected by the research vessel Vidal Gormaz (identifier: CCVG) during three cruises completed in 1996, 1997 and 1998. The data provided to the Florida State University Data Assembly Center (DAC) by R. Rojas (Chilean Navy) included digitized bridge observations. These data were converted to standard DAC netCDF format. The data were then processed using an automated screening program, which added quality control flags to the data, highlighting potential problems. Finally, the Data Quality Evaluator (DQE) reviewed the data and current flags, whereby flags were added, removed, or modified according to the judgment of the DQE and other DAC personnel. Details of the quality control procedures can be found in Smith et al. (1994). The data quality control report summarizes the flags for the Vidal Gormaz meteorological data, including those added by the WOCEMET preprocessor, and the DQE.


 



 

DATA VARIABLES

The Vidal Gormaz data includes observations taken every fifteen minutes, or as provided by the CCVG. Values for the following variables were collected:

Time

Latitude

Longitude

Air Temperature

Sea Temperature

Relative Humidity

Atmospheric Pressure

Earth Relative Wind Direction

Earth Relative Wind Speed

(TIME)

(LAT)

(LON)

(T)

(TS)

(RH)

(P)

(DIR)

(SPD)

 


 



 

1996 FLAG SUMMARY

Statistical Information:

Details of the 1996 cruise are listed in Table 1 and include the cruise dates, number of records, number of values, number of flags, and total percentage of data flagged. A total of 2,196 values were evaluated with 40 flags added by both the preprocessor and the DQE resulting in 1.82% of the values being flagged.

Table 1: Statistical Cruise Information

Cruise Identifier

Cruise Dates

Number of Records

Number of Values

Number of Flags

Percent Flagged

SR_01_/12

11/30/96 12/04/96

244

2,196

40

1.82

Summary:

The 1996 bridge data from the Vidal Gormaz proves to be of excellent quality with 1.82% of the reported values flagged for potential problems. The distribution of flags for each variable are detailed in Table 2.

Table 2: Number of Flags and Percentage Flagged for Each Variable

Variable

G

S

Total Number of Flags

Percentage of Variable Flagged

TIME

LAT

LON

T

TS

RH

P

DIR

SPD

 

 

 

 

34

 

 

 

2

1

1

 

1

1

 

 

 

2

35

1

 

1

1

0.00

0.00

0.00

0.82

14.34

0.41

0.00

0.41

0.41

Total Number of Flags

34

6

40

 

Percent of All Values Flagged

1.55

0.27

1.82

 

G-flags:

Sea temperature (TS) was assessed 34 G-flags by the preprocessor during the SR_01_/12 cruise. The DQE felt these flagged values were realistic, as they were approximately three degrees Celsius lower than the climatological data value and were left in place to highlight extreme sea temperatures. The G-flags emphasize values that are greater than four standard deviations from the climatological mean (da Silva et al. 1994).

Spikes:

Isolated spikes occurred in a few of the variables. Spikes may arise with bridge data when recorded values are written down incorrectly. These individual points were assigned the S-flag.


 



 

1997 FLAG SUMMARY

Statistical Information:

Details of the 1997 cruise are listed in Table 3 and include the cruise dates, number of records, number of values, number of flags, and total percentage of data flagged. A total of 7,335 values were evaluated with 122 flags added by both the preprocessor and the DQE resulting in 1.66% of the values being flagged.

Table 3: Statistical Cruise Information

Cruise Identifier

Cruise Dates

Number of Records

Number of Values

Number of Flags

Percent Flagged

PR_14_/07

03/15/97 04/09/97

815

7,335

122

1.66

Summary:

The 1997 bridge data from the Vidal Gormaz proves to be of excellent quality with 1.66% of the reported values flagged for potential problems. The distribution of flags for each variable are detailed in Table 4.

Table 4: Number of Flags and Percentage Flagged for Each Variable

Variable

G

Total Number of Flags

Percentage of Variable Flagged

TIME

LAT

LON

T

TS

RH

P

DIR

SPD

 

 

 

2

120

 

 

 

2

120

0.00

0.00

0.00

0.25

14.72

0.00

0.00

0.00

0.00

Total Number of Flags

122

122

 

Percent of All Values Flagged

1.66

1.66

 

 

G-flags:

Note: During the PR_14_/07, the ship traversed south of 40 degrees South Latitude. In this region of the globe, little information is known about the climatology, as the data is sparse. Consequently, the G-flagged data values may be realistic, though extreme observations.

G-flags are assessed to values that are greater than four standard deviations from the climatological mean (da Silva et al. 1994). Air temperature (T) was assessed two G-flags by the preprocessor during the PR_14_/07 cruise. The DQE felt these flagged values were realistic, as they were approximately five degrees Celsius higher than the climatological data value and were left in place to highlight extreme air temperatures.

Sea temperature (TS) received 120 G-flags during the PR_14_/07 cruise. The flagged values were approximately two to four degrees Celsius lower than the climatological value. These flagged values were left in place to highlight extreme sea temperatures.


 



 

1998 FLAG SUMMARY

Statistical Information:

Details of the 1998 cruise are listed in Table 5 and include the cruise dates, number of records, number of values, number of flags, and total percentage of data flagged. A total of 1,422 values were evaluated and no flags were added by the preprocessor or the DQE resulting in 0.00% of the values being flagged.

Table 5: Statistical Cruise Information

Cruise Identifier

Cruise Dates

Number of Records

Number of Values

Number of Flags

Percent Flagged

SR_01_/14

12/10/98 12/13/98

158

1,422

0

0.00

Summary:

The 1998 bridge data from the Vidal Gormaz proves to be of excellent quality with 0.00% of the reported values flagged for potential problems.


 



 

FINAL DISCUSSION

The Vidal Gormaz data were found to be very reliable, although ship relative data were not available to assess these meteorological variables for specific problems such as, flow distortion and ship heating.


 



 

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 32306-2840

da Silva, A.M., C.C. Young and S. Levitus, 1994: Atlas of Surface Marine Data 1994, Volume 1:
      Algorithms and Procedures.
NOAA Atlas Series.


 



 

APPENDIX

The following modifications were made to the Vidal Gormaz Bridge data when they were converted from digitized bridge observations to standard DAC netCDF format.

1996

Observations which were left blank were assigned missing data values of (-9999).

On 12/01/96 the times 24:10-24:55 were changed to 00:10-00:55. The date was correct so no changes were made to the date.

On 12/01/96 the time 24:00 was changed to 00:00 and the date was changed to 12/02/96.

On 12/02/96 the times 24:15-24:30 were changed to 00:15-00:30. The date was correct so no changes were made to the date.

On 12/02/96 the time 24:00 was changed to 00:00 and the date was changed to 12/03/96.

On 12/04/96 the times 24:10-24:55 were changed to 00:10-00:55.

1997

Wind directions which were reported as "calma" were changed to 00.

Any observations reported as "s.i" were changed to missing (-9999).

On 03/25/97 one line of data was missing a time stamp. An observation of time is required by the DAC, so the entire record was deleted.

On 03/01/97 the times 00:00-04:00 had dates ranging from 03/31/97-03/01/97. The dates were changed to chronological order 03/31/97-04/01/97.

The data for 04/06/97 04:25 was omitted from the data set because all of the data was reported as "s.i".

1998

On 12/10/98 24:00 the date and time were changed to 12/11/98 00:00

On 12/12/98 24:00 the date and time were changed to 12/13/98 00:00