Metadata Limitations and the effect on XBT depth adjustment

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

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

3. 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 1.0336 CSIRO. Insert presentation title, do not remove CSIRO from start of footer

4. 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 1.0336 CSIRO. Insert presentation title, do not remove CSIRO from start of footer

5. Issues affecting depth correction decisions • 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 • 37678 profiles were screened CSIRO. Insert presentation title, do not remove CSIRO from start of footer

6. Metadata issues – con. • Profiles from GTSPP best copy – 37378 profiles • Profiles with DPC$03 or no DPC$ – 18933 profiles CSIRO. Insert presentation title, do not remove CSIRO from start of footer

7. 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

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

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

10. 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

11. 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

12. 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. CSIRO. Insert presentation title, do not remove CSIRO from start of footer