1. XBT/CTD Comparisons LCDR. Chin-lung Fang OC 3570
Operational Oceanography

2. Contents Introduction Data Quality Control Processing and Discussion
Temp comparison
Depth comparison
Conclusions

3. Introduction Insruments Locations Sea Bird CTD T-7 Sippican XBTs
35 CTDs
Co-located

4. Introduction Insruments Locations Sea Bird CTD T-7 Sippican XBTs
35 CTDs
Co-located

5. Data Quality Control Visual inspection Using MATLAB Final evaluation
28 pairs of data remain
Normal data profile
Bad data profile

6. Data Quality Control Visual inspection Using MATLAB Final evaluationZn
Tn+1 Tn
Tn-1
Visual inspection
Using MATLAB
Final evaluation
28 pairs of data remain
Zn-1
Pn-1 Zn Pn
Zn+1
Pn+1
If |Tn - ( Tn+1 + Tn-1 ) /2| > 2 Std. (~0.2°C)
Then Pn = Possible bad data point
Total 83 points were found

7. Data Quality Control Visual inspection Using MATLAB Final evaluation
28 pairs of data remain
Possible bad data point

8. Processing and DiscussionZn
Temp comparison
Converting P(db) to D(m)
Linear interpolation
Findings
Composite results
Separate results
T effects
Comparing previous studies
Depth comparison
CTD
XBT
Depth(db)
Temp(°C)
Depth(m) 2
0.7
13.2 4
1.3
12.68 6
2.0
12.41 :
Z=(1-C₁)*P-C₂P²
Where C₁=( sin²Φ)*10⁻³; Φ is latitude;
C₂= 2.21*10⁻⁶
by Saunders (1981)

9. Processing and Discussion
CTD
XBT
Depth(m)
Temp(°C)
1.9845
0.7
13.2
3.9690
1.3
12.68
5.9535
2.0
12.41 :
Temp comparison
Converting P(db) to D(m)
Linear interpolation
Findings
Composite results
Separate results
T effects
Comparing previous studies
Depth comparison
CTD
XBT
Depth(m)
Temp(°C)
1.9845
3.9690
5.9535 :

10. Processing and Discussion
Temp comparison
Converting P(db) to D(m)
Linear interpolation
Findings
Composite results
Separate results
T effects
Comparing previous studies
Depth comparison

11. Processing and Discussion
Temp comparison
Converting P(db) to D(m)
Linear interpolation
Findings
Composite results
Separate results
T effects
Comparing previous studies
Depth comparison

12. Processing and Discussion
Temp comparison
Converting P(db) to D(m)
Linear interpolation
Findings
Composite results
Separate results
T effects
Comparing previous studies
Depth comparison
T-4: = =
T-7: = =

13. Processing and Discussion
Temp comparison
Converting P(db) to D(m)
Linear interpolation
Findings
Composite results
Separate results
T effects
Comparing previous studies
Depth comparison
T   T. diff.
T   T. diff. 

14. Processing and Discussion
Studies
Depth(m)
Mean(°C)
Std(°C)
Schmeiser
08/2000
25-125
0.3598
0.1981
0-760
0.2151
Roth
02/2001
0.1779
0.0960
0.1047
Boedeker
08/2001
0.5135
0.2157
0.2147
Fang
07/2002
0.4123
0.1172
0.1546
Temp comparison
Converting P(db) to D(m)
Linear interpolation
Findings
Composite results
Separate results
T effects
Comparing previous studies
Depth comparison

15. Processing and Discussion
CTD
XBT
Depth(m)
Temp(°C)
1.9845
3.9690
5.9535 :
Temp comparison
Depth comparison
Linear interpolation
Findings
Results
Relating to T and T diff. .
CTD
XBT
Depth(m)
Temp(°C)
0.7588
15.00
0.7587
0.7763
14.98
0.7671
0.7885
14.96
0.7755 :

16. Processing and Discussion
Temp comparison
Depth comparison
Linear interpolation
Findings
Results
Relating to T and T diff. .
T-4: = =
T-7: = =

17. Processing and DiscussionT
T-7 Depth diff.
T-7 Temp diff.
Temp comparison
Depth comparison
Linear interpolation
Findings
Results
Relating to T and T diff. .
Simple Formularized-Relation among there 3 terms:
Effects of T
Effects on Temp diff. *
Effects of Depth diff. =

18. Processing and DiscussionT
T-4 Depth diff.
T-4 Temp diff.
Temp comparison
Depth comparison
Linear interpolation
Findings
Results
Relating to T and T diff. .
Simple Formularized-Relation among there 3 terms:
Effects of T
Effects on Temp diff. *
Effects of Depth diff. =

19. Conclusions
This is similar to results obtained from previous OC3570 cruises
XBT Temp. were systematically higher than those recorded by the CTD
°C for T-4 XBT
°C for T-7 XBT
Std. for T-4 is 1.5 times larger than the std. for T-7
XBT depth errors exist
m for T-4 XBT
m for T-7 XBT
Stronger T  larger Temp. diff.
e.g. The greatest bias was in the upper levels

20. ? ? ? ? ?
Questions ?

21. Thanks for your attention !!