1. JCOMM SOT-4 April 2007 XBT Data Acquisition System Intercomparison JCOMM/SOT-4 Scientific and Technical Session Derrick Snowden Gustavo Goni Molly Baringer

2. JCOMM SOT-4 April 2007 Cruise Purpose/Participants Assess the impact of changing two elements of the standard xbt data collection system by comparing the results from six distinct systems with each other and with a higher accuracy Conductivity Temperature Depth (CTD) system. NOAA/AOML, SIO, CSIRO

3. JCOMM SOT-4 April 2007 XBT Data Collection System 1.AOML/DOS 2.Scripps/DOS 3.SEAS2000 4.CSIRO Devil 1.AOML Autolauncher 2.Scripps Autolauncher 3.Sippican LM3A Hand launcher 1.MK12 2.MK21 3.CSIRO Devil Controller SoftwareDigitizer/Recorder Launchers

4. JCOMM SOT-4 April 2007 CTD System SBE 25 Internally logging CTD Sample rate 8 Hz raw data, reduced data 1m Pressure offset on deck is negligible (-.08 to.06 dbars)

5. JCOMM SOT-4 April 2007 Instruments List System NameLauncher TypeRecorder TypeController Software (PC) aomlautoAOML Autolauncher MK-12AOML (DOS 386 PC) devilhandSippican LM-3ADevilDevil Software (Win XP PC) seasautoAOML Autolauncher MK-21SEAS2000 (WinXP PC) seashandSippican LM-3AMK-21SEAS2000 (Win XP PC) sioautoSIO Autolauncher MK-21SEAS2000 (Win XP PC) siok98SIO Autolauncher MK-12 K98 Software (DOS 386 PC)

6. JCOMM SOT-4 April 2007 Station Drop Plan 7 CTD Stations 366 XBT profiles

7. JCOMM SOT-4 April 2007 Drop Summary InstrumentTotal ProfilesTrimmed at z< 500m Trimmed at z<150m aomlauto6522 devilhand5233 seasauto6852 seashand5410 sioauto59101 siok986864 Totals3662712

8. JCOMM SOT-4 April 2007 Regional Characteristics 0 900 Depth (m) Mean CTD T(z) 5 20 Approx Station Catalina Island SCMI/Port of LA

9. JCOMM SOT-4 April 2007 MSE Bias Variance

10. JCOMM SOT-4 April 2007 Partitioning XBT Error XBT differs from the CTD due to : A: inaccurate depth measurements B: inaccurate temperature measurements A B Probe fall rate error Thermistor calibration error Signal digitization error Geophysical noise

11. JCOMM SOT-4 April 2007 Magnitude of Expected Errors Temperature accuracy 0.1 deg C (red curve) 0 800 Depth (m) 0.250 Depth accuracy is 2% of the total depth

12. JCOMM SOT-4 April 2007 XBT/CTD Profiles

13. JCOMM SOT-4 April 2007 Temperature Error: Isostads Attempt to isolate the temperature error by concentrating on depths where the temperature gradients are minimal After Heimiller et al 1983

14. JCOMM SOT-4 April 2007 Isostad Analysis (cont’) 1.aomlauto 2.devilhand 3.seasauto 4.seashand 5.sioauto 6.siok98

15. JCOMM SOT-4 April 2007 Corrected Profiles: Isostads 1.aomlauto 2.devilhand 3.seasauto 4.seashand 5.sioauto 6.siok98

16. JCOMM SOT-4 April 2007 Conclusions Temperature error is within manufacturer specs for all instruments (In the deepest thermostad the mean offset was less than 0.055 degC for all instruments). There is a detectable bias that is in part due to fall rate error. Correcting the fall rate equation reduces the mean differences well below manufacturer specs and published results in all cases. Two instruments (aomlauto, and devilhand) had mean offsets that were appreciably lower than the other four instruments.

17. JCOMM SOT-4 April 2007 Participants NameAffiliationEquipment/Responsibility Steve CookNOAA/AOMLSEAS2K Hand Launcher Derrick SnowdenNOAA/AOMLData collection and analysis/Backup CTD Janet RoseliNOAA/AOMLSEAS2K Software support and Autolauncher operation Uli RiveroNOAA/AOMLAOML/DOS Autolancher Carrie WolfeSCMIAOML/SEAS2K Autolauncher Glenn PezzoliUCSD/ScrippsSIO/SEAS2K Autolauncher Valerie CannonUCSD/ScrippsSIO/SEAS2K Autolauncher/Backup AOML/SEAS2K Autolauncher Bob BeattieCSIROCSIRO Devil Handlauncher Adam WillinghamSCMISBE-25 CTD

18. JCOMM SOT-4 April 2007 MSE Bias Variance