© Crown copyright Met Office Ensemble of subsurface databases Simon Good, presented by Nick Rayner, ERA-CLIM workshop on observation errors, Vienna, April th 2012.

© Crown copyright Met Office Construction of a subsurface dataset involves many choices Choice of data sources ? Duplicate profile detection ? Thinning/ interpolation to standard levels ? Quality control procedures ? How to adjust for biases ? Different choices are made for each dataset (EN3/WOD/CORA etc.), so each is different to the other How much does this uncertainty impact applications? Etc…

© Crown copyright Met Office Assessing the impact of dataset construction uncertainty To understand the impact, we can apply each dataset to an application The range of outcomes indicates the uncertainty This is the ‘ensemble of opportunity’ approach This is currently not straightforward to do since: Different datasets use different file formats In the case of bias adjustments for XBT and MBT data, it is often necessary to apply methods described in papers to the datasets It is inefficient for each user to do this individually The aim of deliverable 4.7 is to overcome these issues by compiling the ensemble of opportunity and providing it to users

© Crown copyright Met Office Current status XBT and MBT bias adjustments have been applied to the EN3/EN4 dataset resulting in multiple versions of the data, each in the same file format Plot shows the result of applying the ensemble to calculate global upper ocean temperature anomaly Other datasets e.g. WOD are being converted to the EN3/EN4 file format

© Crown copyright Met Office What is the best way to provide the ensemble to users? Simplest option is to provide each dataset separately in the same format (e.g. the EN3/EN4 file format) Inefficient as there is much repeated information in each realisation of the data It is not easy to compare the realisations Would another option be more useful? E.g. holding all the datasets in a single database How do users wish to obtain the data? E.g. download all the data at once, separate set of files for each dataset?