1 / 19

Revisiting the XBT Fall Rate Equation (Sippican Deep Blue):Implications and Recommendations

Revisiting the XBT Fall Rate Equation (Sippican Deep Blue):Implications and Recommendations. JCOMM/SOT-4 Derrick Snowden Gustavo Goni Molly Baringer. Outline. Introduction to the data XBT Error Partioning Estimating a New Fall Rate Equation Implications for Climate Studies

teddy
Download Presentation

Revisiting the XBT Fall Rate Equation (Sippican Deep Blue):Implications and Recommendations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Revisiting the XBT Fall Rate Equation (Sippican Deep Blue):Implications and Recommendations JCOMM/SOT-4 Derrick Snowden Gustavo Goni Molly Baringer

  2. Outline • Introduction to the data • XBT Error Partioning • Estimating a New Fall Rate Equation • Implications for Climate Studies • Conclusions and Recommendations

  3. System Name Launcher Type Recorder Type Controller Software (PC) aomlauto AOML Autolauncher MK-12 AOML (DOS 386 PC) devilhand Sippican LM-3A Devil Devil Software (Win XP PC) seasauto AOML Autolauncher MK-21 SEAS2000 (WinXP PC) seashand Sippican LM-3A MK-21 SEAS2000 (Win XP PC) sioauto SIO Autolauncher MK-21 SEAS2000 (Win XP PC) siok98 SIO Autolauncher MK-12 Instruments List 366 total profiles

  4. XBT/CTD Profiles

  5. Outline • Introduction to the data • XBT Error Partioning • Estimating a New Fall Rate Equation • Implications for Climate Studies • Conclusions and Recommendations

  6. Partitioning XBT Error XBT differs from the CTD due to : A: inaccurate depth measurements B: inaccurate temperature measurements A B

  7. Fall Rate Equation a: Change of mass of the probe due to spooling wire. b: Probe geometry and initial terminal velocity c: Describes startup transients i.e. initial conditions Currently used FRE (WMO 1770:52) for Deep Blue probes contains no constant term ( c ).

  8. Fall Rate Error: Initial Conditions Hallock and Teague 1992

  9. Outline • Introduction to the data • XBT Error Partioning • Estimating a New Fall Rate Equation • Implications for Climate Studies • Conclusions and Recommendations

  10. Determining Depth Offset Focus on the temperature gradient: derivative of temperature with respect to depth Minimize temperature error effect

  11. Depth Offset Prior to Correction

  12. Depth Correction Algorithm • Assemble the depth offsets (dZ) • Recalculate XBT depths Znew = Zxbt+dZ • Back calculate time (t) • Fit new fall rate equation to (t) z = at^2 + bt + c

  13. Depth Offset: Post-Correction

  14. Summary of Fall Rate Coefficients 1: Taken from Hanawa et al 1995

  15. Outline • Introduction to the data • XBT Error Partioning • Estimating a New Fall Rate Equation • Implications for Climate Studies (Wijffels and Thresher 2007) • Conclusions and Recommendations

  16. Basin Averaged Offset

  17. Global Trends

  18. Recommendations • Future Work: Tropical Atlantic Cruise (May 2007) will conduct additional side by side XBT-CTD comparisons • Reinvorgorate research toward understanding fall rate issues • Metadata to include coefficients and the form of the equations (it isn’t sufficient to list A,B need to know z=at^2 + bt + c + … (including exchange files and metadata servers) • Quality flags should be listed level by level not just for the entire profile • Communication with the manufacturers to better understand the timing and nature of changes in XBT manufacturing procedures.

  19. Implications for Climate Studies A B

More Related