Metadata Limitations and the effect on XBT depth adjustment A. Gronell and R. Cowley CSIRO Marine and Atmospheric Research

CSIRO. Insert presentation title, do not remove CSIRO from start of footer Why we’re interested:

CSIRO. Insert presentation title, do not remove CSIRO from start of footer Depth correction: We need entire database to same vertical scale We do this by converting all t-7, deep blue, t-6 and t-4 profiles to conform to the Hanawa ‘85 equations High or full vert resolution depths are recalculated and replaced. Low vert resolution data depths are multiplied by

CSIRO. Insert presentation title, do not remove CSIRO from start of footer Depth correction procedures: High vertical resolution profiles with ‘known’ probe type : ‘fixes’ profiles with truncated or rounded depths. Replace depths with calculated depths. All depths now to.01 resolution Low resolution profiles that either need correction (DPC$01) or are of unknown probe type and fit the criteria for correction: Multiply depths by

CSIRO. Insert presentation title, do not remove CSIRO from start of footer Inadequate Metadata is currently the biggest hurdle GTSPP best copy datasets for IO were downloaded and run through Depth correction software Anything that was not straight-forward was revisited profiles were screened Issues affecting depth correction decisions

CSIRO. Insert presentation title, do not remove CSIRO from start of footer Metadata issues – con. Profiles from GTSPP best copy – profiles No probe type info18303Action depends on date and max depth PEQ$ missing but determined from elsewhere and added 11442Action depends on probe type determined Missing DPC$ field156Action depends on date and max depth Profiles with DPC$03 or no DPC$ – profiles 1000m OR post Do not change depths >200m AND <1000m AND pre Change depths

CSIRO. Insert presentation title, do not remove CSIRO from start of footer Metadata problems found in GTSPP best copy dataset CTDs that were identified as XBTs – this is a problem if the DPC$ field is 03 and they fit our other criteria T10 profiles that go to 1500m (actually t-5 probes) MBTs misidentified (probably XBTs) – max depth for MBTs is ~250m

CSIRO. Insert presentation title, do not remove CSIRO from start of footer MBTs that go deeper than 300m Red profiles are post 1975

CSIRO. Insert presentation title, do not remove CSIRO from start of footer MBT distribution in the Indian Ocean through time

CSIRO. Insert presentation title, do not remove CSIRO from start of footer Other issues Number of depths wrong – more or fewer in the parameter field Additional or missing depths – in full resolution profiles, depths duplicated or missing Deep_depth field value different from the actual deepest depth Single point profiles Profiles with exactly.6m resolution (depths assigned and not calculated?) – results in error of ~30m at 800m

CSIRO. Insert presentation title, do not remove CSIRO from start of footer Conclusions: Codes are confusing – there are too many places to find probe type information PEQ$ PRT$ FRE$ PTY$ PFR$ We should be able to reconcile all these into a sensible PEQ$, even if it’s unknown. DPC$ need clarification – 03 = not enough information, do not correct – but we know most of these should be corrected. 02 = known probe type, no correction – what does this mean? No correction done or no correction necessary?

CSIRO. Insert presentation title, do not remove CSIRO from start of footer Conclusions (con): To effectively calculate the corrections needed to fix the fall rate bias of XBTs, we need the best quality baseline data – all using the same base-line fall rate. We therefore need smart methods to get all profiles to the Hanawa equation. We can only do this if we have adequate metadata – otherwise, we’re just making educated guesses.