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EN3 quality controlled ocean data: Files

Profile files

The profile files contain observed profile data for a particular month and quality control decisions for those profiles. Some data thinning has been applied to the original profile data: a single profile for each day is averaged from the data from moored buoys that report very frequently and for data with high vertical resolution the profiles are subsampled to retain a maximum of 150 levels. Only one profile is stored within 0.2 degrees in latitude and longitude and 1 hour. Data from the ASBO project only have the day of observation so in this case only one profile is allowed per day. The profile that is retained is determined using a number of factors such as which has the most levels, which goes the deepest, the source catalogue (e.g. Argo delayed mode data are preferred to Argo realtime profiles). More information can be found in Ingleby and Huddleston (2007).

The table below describes the variables that can be found in the NetCDF files.

NetCDF variable	Description
JULD	Date of observation in days since midnight on 1/1/1950.
LATITUDE	Latitude at which profile was recorded.
LONGITUDE	Longitude at which profile was recorded.

DEPH_CORRECTED	A two-dimensional array containing the depth of each level of each profile.
TEMP	A two-dimensional array containing the observed temperature of each level of each profile.
POTM_CORRECTED	A two-dimensional array containing the potential temperature of each level of each profile.
PSAL_CORRECTED	A two-dimensional array containing the salinity of each level of each profile.
BKPT	A two-dimensional array containing the background potential temperature used in the quality control of each level of each profile.
BKPS	A two-dimensional array containing the background salinity used in the quality control of each level of each profile.
POSITION_QC	This is a string with a character for each profile. If a profile has a '4' in this field, the entire thing should be rejected.
PROFILE_POTM_QC	This is a string with a character for each profile. If a profile has a '4' in this field, the entire temperature profile should be rejected.
PROFILE_PSAL_QC	This is a string with a character for each profile. If a profile has a '4' in this field, the entire salinity profile should be rejected.
POTM_CORRECTED_QC	This is an array of strings, one for each profile. Each string has a character for each level. If a level has a '4' in this field, the temperature should be rejected.
PSAL_CORRECTED_QC	This is an array of strings, one for each profile. Each string has a character for each level. If a level has a '4' in this field, the salinity should be rejected.
QC_FLAGS_PROFILES	This contains detailed information about the quality decisions affecting an entire profile. Each bit within the number has a different meaning if set. The meanings are described in the QC_FLAGS_PROFILES table.
QC_FLAGS_LEVELS	This contains detailed information about the quality decisions affecting individual levels of a profile. Each bit within the number has a different meaning if set. The meanings are described in the QC_FLAGS_LEVELS table.
REFERENCE_DATE_TIME	The observation times are relative to this time (currently 1/1/1950).
PROJECT_NAME	The start of this field gives information about the source of each profile - it might read 'ARGO', 'GTSPP', 'WOD05' or 'ASBO'. The rest of the field contains additional information e.g. the character after 'ARGO' might be 'R', 'A' or 'D' to indicate real-time, real-time adjusted or delayed-mode data. The two characters after 'GTSPP' and 'ASBO' are from http://www.nodc.noaa.gov/GTSPP/document/codetbls/gtsppcode.html#ref082. For 'WOD05', the three next characters are the instrument type. There are two numbers after the instrument type for WOD05 data. The first is the country code (see Appendix 1 from the WOD05 documentation) and the second the platform.
PLATFORM_NUMBER	A unique identifier for each instrument.
INST_REFERENCE	For GTSPP this contains the WMO code table 1770 type. Based on the GTSPP metadata two additional code values are used: 101 - unknown instrument type, fall-rate coeff A=6.472 assumed; 102 - unknown instrument type, no fall-rate correction required. For WOD05 this is 10000Sech29 + 10InstType + CorrType, where: Sech29 (secondary header 29) is probe type (0-16) - table 2.13 (p 89) in WOD05 documentation; InstType (variable specific secondary headers) is probe type (1-803) - table 3.2 (p 103) in WOD05 documentation and CorrType is derived from Sech54 (secondary header 54) - "Needs depth fix" table 2.20 (p 93) in WOD05 documentation. Sech54 = 0: CorrType = 0 ! No correction needed Sech54 = 1: CorrType = 1 ! XBT Hanawa et al (1995) correction () Sech54 = 2: CorrType = 2 ! XBT Kisu et al (2005) correction () Sech54 = 103: CorrType = 3 ! XCTD Johnson (1995) correction () Sech54 = 104: CorrType = 4 ! XCTD Mizuno and Watenabe (1998) correction () Sech54 = -1: CorrType = 9 ! Insufficient information - no correction (Note: we correct the depths of profiles with CorrType 1 and 2, for CorrType 1 this is modfied for "cold" profiles, see section 3.1 of Ingleby and Huddleston (2006). We do not currently correct CorrType 3 and 4 - XCTDs.)
WMO_INST_TYPE	Contains a simplified subset of WMO code table 1770. It is recommended that the INST_REFERENCE field is used to separate data types, as these are only broad categories and some profiles may not be in the correct category. 401 - XBT/MBT 741 - TESAC 831 - Profiling floats and other data e.g. some marine mammal data 820 - BUOYS
SCIENTIFIC_CALIB_COEFFICIENT	For expendable bathythermographs (XBTs) this variable contains the multiplication factor used to correct the depths (except for TSK T5 XBTs where the multiplication factor depends on depth; in this case this field will specify a correction of 0.955).

Meaning of the QC_FLAGS_PROFILES values

This field contains detailed quality information about each profile. To interpret these numbers, imagine them as 32 bit binary numbers (i.e. a 32 digit number made up of either zeroes or ones). If a bit is 'set' it has value 1, otherwise it has value 0. The least significant digit is bit 0 and the most significant digit is bit 31. Each bit has a meaning as described in the table below. For example if a salinity profile is rejected then bit 1 is set. There will also be other bits set to say which quality control tests have been failed. In this example, lets assume that this profile was rejected because it is on the Argo grey list and hence bit 17 is also set. In decimal the resulting quality code will be 2^1 (bit one is set) + 2^17 (bit 17 is set) = 131074.

More information about the different checks can be found in Ingleby and Huddleston (2007).

Bit	Meaning if set

0	Temperature profile was rejected.
1	Salinity profile was rejected.
3	Temperature and salinity rejected by the track check.
4	Temperature and salinity rejected by the vertical stability check.
5	Temperature and salinity rejected because profile is on the altimetry quality control suspect list.

9	Temperature was rejected because profile is on the Argo grey list.
10	Temperature rejected because the profile is on the EN3 reject list.
11	Temperature profile rejected by the vertical check (which looks for spikes etc).
12	Temperature rejected because there were no background values for this profile.
13	Temperature profile rejected because over half its levels were rejected.
17	Salinity was rejected because profile is on the Argo grey list.
18	Salinity rejected because the profile is on the EN3 reject list.
19	Salinity profile rejected by the vertical check (which looks for spikes etc).
20	Salinity rejected because there were no background values for this profile.
21	Salinity profile rejected because over half its levels were rejected.
24	Information flag to say that a correction was applied to depths - expendable bathythermograph (XBT) profiles only.
25	Information flag to say that this is a superob - an average of multiple observations; for moored buoys only.

Meaning of the QC_FLAGS_LEVELS values

The table below describes the meaning of the bits for the QC_FLAGS_LEVELS variable, which provides detailed quality control about the individual levels of each profile. See the QC_FLAG_PROFILES section for information about how to interpret the data.

Bit	Meaning if set

0	Temperature level was rejected.
1	Salinity level was rejected.
8	Temperature level was rejected because it is a bathythermograph measurement shallower than 4 m or deeper than 950 m.
9	Temperature level rejected because it was rejected by the Argo delayed mode quality control procedures.
10	Temperature was out of a reasonable range and was set to missing data.
11	Temperature level was rejected because it was on the EN3 reject list.
12	Temperature level was rejected by the vertical check (spikes etc).
13	Temperature level was rejected because no background value was available.
14	Temperature level was rejected by the Bayesian background check performed on reported levels.
15	Temperature level was rejected by the Bayesian and buddy checks performed on standard levels.
16	Temperature level was reinstated after rejection by the Bayesian and buddy checks performed on standard levels.
20	Salinity level was rejected because it is a bathythermograph measurement shallower than 4 m or deeper than 950 m.
21	Salinity level rejected because it was rejected by the Argo delayed mode quality control procedures.
22	Salinity was out of a reasonable range and was set to missing data.
23	Salinity level was rejected because it was on the EN3 reject list.
24	Salinity level was rejected by the vertical check (spikes etc).
25	Salinity level was rejected because no background value was available.
26	Salinity level was rejected by the Bayesian background check performed on reported levels.
27	Salinity level was rejected by the Bayesian and buddy checks performed on standard levels.
28	Salinity level was reinstated after rejection by the Bayesian and buddy checks performed on standard levels.

Analysis files

The analysis files contain objective analyses produced using optimal interpolation of the profile data for a particular month and a persistence forecast background. More details can be found in Ingleby and Huddleston (2007). The analyses are produced on a regular 1 degree latitude/longitude grid and have 42 levels in the vertical. To reduce storage space not all latitudes are saved in the files.

The table below describes the variables in the NetCDF files.

NetCDF variable	Description
depth	The depth of each level (m).
lat	The (centre) latitudes of the grid points (degrees).
lon	The (centre) longitudes of the grid points (degrees).
temperature	The potential temperature at each grid point.
salinity	The salinity at each grid point.

Details

Introduction

This page describes the EN3 files. The files are in NetCDF format and contain a number of variables and attributes. The tables on the left list the most important of these.

Quality control information

To make correct use of the profile data, the quality control flags must be read and applied. There are two ways to do this:

Use the POSITION_QC, PROFILE_POTM_QC, PROFILE_PSAL_QC, POTM_CORRECTED_QC and PSAL_CORRECTED_QC variables. These have values of either '1' (accept) or '4' (reject) (or '0' where there were no data and hence no quality control was performed).
Use the QC_FLAGS_PROFILES and QC_FLAGS_LEVELS fields. These contain numeric values that say if the whole profile or an individual level has been rejected (bit 0 set if temperature is rejected, bit 1 if salinity is rejected), and also give information on why something was rejected.

Older versions of the dataset

This page has been written for version EN3_v2a of the dataset but is also applicable for the previous versions. However, please note that the detailed quality control flags are not available and there are no analysis files for download for the older versions. The EN3_v1d_WijffelsXBTCorr dataset has an additional field, as described in its download page. It is also important to be aware that some of the metadata are incorrect for the EN3_v1c dataset; more details are on its download page and in the old page about file formats.

Old version of this page

The old version of this page can be accessed here.

Quick links

View profile file information
Meaning of quality control flags applicable to whole profiles
Meaning of quality control flags applicable to individual levels in profiles
View analysis file information

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