© Crown copyright Met Office An ocean database of surface / sub-surface temperature and salinity...

© Crown copyright Met Office

An ocean database of surface / sub-surface temperature and salinity observations (D4.5)

Chris Atkinson and Nick Rayner

• Prototype ocean database due June 2013 for ERA-CLIM

• Will include data from ICOADS 2.5 (surface) and EN4 (sub-surface), 1900-present

• Other surface salinity sources will be added (GOSUD, ICES)

• Observations will include quality control flags, bias adjustments and estimates of measurement uncertainty

• The database will be designed flexibly, allowing new fields or layers to be added as required, e.g. observation minus background fields from reanalyses as they become available.

• The database is envisaged as a resource for the reanalysis community, but may be useful for forecasting applications (e.g. testing coupled seasonal forecasting systems).


An ocean database of surface / sub-surface temperature and salinity observations

Callsign: shp1234Observation type: ShipInstrument type: BucketLongitude: -45.0Latitude: 26.5Time: 41014.0Depth: 0.2Temperature: 24.3Macro-bias: -0.1Macro-bias uncertainty: 0.05Micro-bias: -0.2Micro-bias uncertainty: 0.05Measurement uncertainty: 0.2Total Uncertainty: 0.3

Example database entry for a surface temperature observation


Basic data:

Includes metadata on observation type where available. For surface observations, a nominal depth may be allocated initially thought this may be improved later


Macro bias:

Bias for an observation (and instrument) type, e.g. observations made by ships using buckets are biased cold due to heat loss to atmosphere during recovery

Surface bias and bias uncertainties based on recent work for the HadSST3 dataset

Subsurface bias and bias uncertainties from EN4, e.g. XBT bias corrections


Micro bias:

Bias for an individual observing platform (e.g. a particular ship). Based on the HadSST3 model for observation uncertainty which assumes a constant bias for each platform

Where this bias cannot be estimated (e.g. through comparison with some background field) the uncertainty will be larger and based on a distribution of possible biases (e.g. as for HadSST3)


Measurement uncertainty:

Random measurement uncertainty for a particular platform (e.g. a particular ship) based on HadSST3 model for observation uncertainty.

Where this uncertainty cannot be estimated (e.g. through comparison with some background field) the uncertainty will be larger and based on a distribution of possible uncertainties (e.g. as for HadSST3)


Total Uncertainty:

A combination (possibly additive) of all other uncertainties representing the total uncertainty in an individual, bias adjusted observation

This will vary from observation to observation

For some high quality sub-surface observations (e.g. from CTDs or Argo floats passing quality control) this may initially be set to zero (or some small value)


Callsign: xbt1234QC flags: 1001100Macro-bias 1: -0.10Macro-bias 2: -0.05Macro-bias 3: -0.02Ob-Bk 1: 0.10Ob-Bk 2: 0.08Measurement uncertainty pdf: [0,0.6,2]

Other Data:

Other fields and layers will be included or can be added to the database as necessary, such as:

QC flags

Several bias estimates (e.g. for XBTs based on various studies)

Ob-Bk fields from different reanalyses

More sophisticated uncertainties (e.g. parameters of pdf’s for non-normal uncertainties)




• The database is currently at the conceptual stage

• Database content and format are not finalised

• Feedback from possible users is very welcome to steer the design and make the database as useful a resource as possible

[email protected]

[email protected]

© Crown copyright Met Office An ocean database of surface / sub-surface temperature and salinity...

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