Operational Oceanography Cruise February 2003 Comparison of Expendable Bathythermograph and Conductivity, Temperature and Depth Profilers LT Jeffrey S. Dixon OC 3570

Sampling Equipment Sippican T7 XBT Sea-Bird SBE911 CTD

Study Process Field Sampling Data Processing Analysis Conclusions Quality Control Analysis Temperature vs. Depth Comparison Comparison to Previous Studies Conclusions Impact on Sound Velocity Profiles The CTD is the Accepted Standard!

Field Sampling 26 XBT/CTD Pairs (2 later thrown out) February 2003 Cruise XBT/CTD Stations 26 XBT/CTD Pairs (2 later thrown out)

Data Processing Used Matlab 53 Code Adaptation / Modification (4 Previous Studies) Interpolation Steps for Common Comparison 2 Step Quality Control Process Visual Inspection of Temperature vs. Depth Comparison to Ambient Temperatures CTD Divides into 383 Equal Depth Levels XBT T7 Max Depth 760 meters

Quality Control – Visual Inspection Natural Variability or Bad Data??

Quality Control – Visual Inspection XBT / CTD Pair 18 Thrown Out

Quality Control – Visual Inspection Less Obvious Problem?

Quality Control – Compare to Ambient Temperature Quantitative Quality Control Measure Temperature of each > or = 0.2 deg C than temperature of the average of two adjacent levels?

Quality Control - Compare to Ambient Temperature Zn Tn+1 Tn Tn-1 Possible Bad Points Zn-1 Pn-1 Zn Pn File generated: Zn+1 Pn+1 Text25.txt XBT 35.7290 flagged 87.3400 flagged 759.0460 bottom CTD 51.6080 flagged 53.6050 flagged 759.0460 bottom If |Tn - ( Tn+1 + Tn-1 ) /2| > 2 Std. (~0.2°C) Then Pn Flagged as Possible bad data point 37 total points were found–but retained (Fang 2002)

Data Analysis – 3 Steps

Average Temperature Difference Greatest Variability Consistent Warm Bias -.1275oC

Temperature Stats - Compare to Previous Studies

Isotherm Depth Difference Temperature deg C 5 6 7 CTD 10 Isotherm Depth Difference ~ 5m XBT 20 30 40

Average Isotherm Depth Difference

Sound Velocity Profile Differences – Impact of XBT Warm Bias

SVP for all XBTs and CTDs Slight Warm Bias Disagreement At Surface XBT CTD Some Qualitative Disagreement

Sound Velocity Profile Differences XBT bias due to warm temperature bias and a constant salinity of 33.5psu as well 0.1275oC temperature increase will increase sound speed 0.51m/s

Conclusions XBT Exhibits Distinct Bias Compared to CTD SVP bias due to both temperature bias and salinity constant Affect on Sound Velocity Profiles is Measurable However: Impact Considered Small! XBT Should Not be Used as a Research Tool XBT Valid Tool to Determine SVP for Navy And Jeff should continue to focus on oceanography because…

…He Can’t Launch Weather Balloons Damn Juan who put that antenna there? Que? Someday I’ll get to go on a research cruise without students.