1. LM Sippican T5 and T10 XBT accuracy measurements preliminary results F.Reseghetti 1, L.Cheng 2, M.Borghini 3, J.Zhu 2 Outlines T5-T10 characteristics Data and methods Lab results (pre) FRE calculations Results (pre) The 4 th XBT workshop: XBT science and the way forward 11-13 November 2014, Beijing, China 1 Enea,UTMAR-OSS, Lerici (Italy) 2 ICCES, IAP-CAS, Beijing (China) 3 CNR,ISMAR, Lerici(Italy)

2. T5 vs T10 (the giant and the dwarf) References (for LM Sippican T5&T10 probes): Stegen et al. (1975); McDowell (1978); Anderson (1980); Joyce (1981); Seaver and Kuleshov (1982); Von Bock (1983); Augstein et al. (1989); Kennelly et al. (1989); Wright and Szabados (1989); Meincke (1991); Boyd and Linzell (1993); Narayanan and Lilly (1993); Ridgway et al. (1999); Cunningham et al. (2000); Pingree (2002); Quartly (2006); Vazquez et al. (2007); Greenan et al. (2007); Machin et al. (2008); Rana (2008). T5 1968 Length:13.50±0.100 in. Central hole diameter:0.423±0.005 in. Nose weight613±1 g (1.351±0.002 lbs.) Nose height overall2.818±0.003 in. Nose height to seam2.370±0.005 in. Nose diameter1.993±0.005 in T10 1971 Length:8.50±0.100 in LM Sippican uses 39 gauge copper wire (having 15% as stretching limit) XBT thermistors are from GE Sensing, having resistance of 5 kΩ at T=25.0°C, working range from 18.5 kΩ (-2.5°C) to 3.2 kΩ (+35.5°C), and accuracy better than 1% in resistance. Five sensors from each lot are measured at two points: 0 ⁰ C and +25 ⁰ C. After Parylene coating, the thermistors have a maximum thermal time constant of 130 ms with water flowing at a maximum rate of 15 feet/second. The thermistor is purchased to require that the sensor meets the temperature/resistance curve through the range of pressures for the probe within ± 0.1°C. LM Sippican receives a certificate of compliance.

3. FRE (available) XBT type /equationA (ms -1 )B (ms -2 )C(ms -3 )D(m) T5 Sippican6.8280.00182 T5 Boyd Linzell6.7050.001619 T5 Boyd Linzell6.7950.0024752.148 10 -6 -1.803 T5 TSK Kizu-Hanawa 2003 6.4751±0.22470.00175±0.00117 T5 TSK Kizu-Hanawa 2005 6.540710.0018691 T5 TSK Miura et al. 2004 6.6220.00230 T 10 Sippican6.3010.00216 T4/T6/T7/DB6.4720.00216 T4/T6/T7/DB IGOSS6.6910.00225 Note that the official error estimated by LM Sippican on depth (2% or 5m, whichever is greater) implies a 5m uncertainty down to 250m depth. This value is the only possible error for T10 probes.

4. Measurements: Results For both T5 and T10 probes, the measured diameter of the central hole is in the range 1.065-1.085 cm (sensitivity 0.005cm), the admitted range is 1.062-1.087 cm. The nose diameter spans from 5.06 to 5.07cm (sensitivity 0.005cm), the admitted range is 5.050-5.075 cm. T5 and T10 probes have the same zinc nose as T4/T6 probes (614.0g in air, ± 1g). The weight of the zinc nose of two T5 failed probes is 613.5 and 614.0g (sensitivity 0.05g), respectively, 613.2 g for the unique available nose from T10 version. The admitted range of variability is 611.9-613.7 g. The range of measured weight in air of T10 probes is 693.7-696.5 g (sensitivity 0.05g). The variability of weight in air for T5 is 972.8-979.5 g for probes manufactured in 2007, 980.1 - 994.9 g and 973.9 - 988.1g for T5/20 manufactured in 2008, 980.3-987.6 for 2010, 980.7-991.6 g for 2014, (the admitted range in air is 997.9 ± 5g and the weight in water, 680.4g). The length of the plastic cylinder connecting the nose with the plastic after-body for T5 probes is ranging from 12.69cm to 12.75cm (sensitivity 0.005cm).

5. Bath calibration Several calibrations done at La Spezia NATO Center (now CMRE) Two different recording systems (MK-21 Usb and MK12) In 2008: the same probes with both the systems In 2011: use of tester to identify also the system bias 2007 06.11 5 T5 Mk21 2007 08.06 4 T5 Mk21 2007 08.07 10 T5 Mk21 2007 09.19 4 T5 Mk21 12.025 +0.054±0.010 12.050 -0.082±0.011 16.076 -0.043±0.020 12.051 +0.058±0.013 14.198 +0.059±0.015 14.026 -0.078±0.009 20.073 -0.070±0.010 13.888 +0.063±0.013 16.107 +0.062±0.012 16.009 -0.072±0.009 18.064 +0.070±0.013 17.990 -0.074±0.008 19.956 +0.075±0.013 20.067 -0.070±0.005 22.017 +0.075±0.017 22.017 -0.067±0.009 24.016 -0.063±0.015 26.075-0.064±0.013 2008 02.04 6T5 Mk21 2008 02.05 6T5 Mk12 2011 04.13 4 T5 Mk21+test 2 T10 Mk21+test 12.883 -0.031±0.014 11.948 +0.039 ±0.021 11.992 +0.002±0.011+0.045±0.015 14.168 -0.026±0.010 13.034 +0.029 ±0.017 16.000 +0.003±0.007+0.040±0.015 16.034 -0.027±0.013 14.022 +0.031 ±0.018 19.812 +0.016±0.010 18.046 -0.011±0.011 16.094 +0.033 ±0.018 24.007 +0.007±0.010 21.064 -0.009±0.011 18.824 +0.041 ±0.020 28.205 +0.000±0.006 24.348 +0.034±0.016 21.012 +0.045 ±0.022 24.090+0.037 ±0.021

6. MK21 bias but variable  2013010915 56 3712.1926.75 2013020412 45 2512.1526.71 12 50 0512.1126.67 12 52 2112.1126.66 12 59 4312.0726.60 13 15 43 D12.1626.72 13 18 1612.0726.62 13 20 3312.0726.61 15 01 14 D12.1926.75 15 10 1412.0626.60 15 27 56 D12.1526.71 15 30 3712.0626.60 2013020508 55 4512.1026.65 09 59 3212.0626.60 10 19 2012.0826.63 2013020909 40 4312.1526.70 09 45 1512.1126.67 10 01 5812.0726.61 10 39 3812.0926.63 10 47 4012.0726.60 2013020910 52 3412.1526.79 11 10 0312.1026.65 11 12 4012.1126.66 11 37 1612.1026.64 11 38 5212.1026.65 2013021810 46 5012.1326.69 10 48 5412.1326.69 16 10 1912.1126.66 2013022814 18 2312.1826.74 2013030611 09 1912.1226.68 2013031808 42 4612.1726.74 10 21 0412.2026.79 10 22 0212.1926.77 2013031906 57 2212.1926.75 2013032008 59 1312.1926.75 2013032814 13 5712.1926.75 2013040308 47 3712.1926.75 09 27 1712.1626.72 09 29 0112.0826.62 09 33 5912.1026.66 09 39 1512.1026.65 2013040409 28 2412.1526.71 09 38 2412.1726.74 09 40 4812.1826.74 11 35 2212.1426.70 11 38 5712.1426.70 11 41 1712.1326.68 2013040508 18 4712.1726.74 08 21 3712.1426.70 2013040601 30 2712.1126.67

7. 136 32.696N21 07.985E2007 07 2223 39 023062192165.7 236 30.007N15 50.017E2007 10 0818 29 123006522249.2 336 30.022N15 49.988E2007 10 0818 41 33306218860.1 436 30.051N15 49.961E2007 10 0818 50 523006502127.3 538 43.360N10 29.571E2007 10 1313 47 243006481996.9 638 11.544N08 47.983E2007 10 1413 57 143062130.1206150.0 738 35.966N06 36.137E2007 10 1508 05 223062160.11962003.7 839 00.314N06 36.232E2007 10 1515 27 023062140.1200353.5 943 33.335N07 49.773E2007 10 2216 09 063005300.11992254.7 1043 09.002N08 14.010E2007 10 2222 32 033005260.1197434.2 1139 46.456N11 40.928E2007 10 2709 29 113062200.12101449.0 1238 54.945N13 17.983E2007 10 2722 56 343005250.12002242.0 1336 33.580N21 05.880E2007 12 1516 40 033331132198.4 1435 51.470N17 48.139E2007 12 2016 53 58333107670.4 1536 29.990N15 50.080E2007 12 1307 55 22306215462.5 1638 37.000N03 38.990E2008 04 0214 33 483331101498.7 1738 48.200N10 15.500E2008 04 0822 03 233331050.1195647.8 1838 48.215N10 15.495E2008 04 0822 13 193331140.1187651.0 1938 54.960N13 18.050E2008 04 0922 23 193006540.12042272.3 2038 54.972N13 18.059E2008 04 0922 33 303331080.11972180.7 2135 13.935N21 28.497E2009 09 1816 49 483330911974.8 2238 16.723N08 57.390E2010 08 0120 07 34333094973.40.11902004.3 2338 12.030N07 48.800E2010 08 0205 32 12333100974.90.1186503.2 2438 06.680N06 38.200E2010 08 0216 01 15333104976.60.11902055.6 2537 50.880N04 04.320E2010 08 0312 41 24333096973.30.11922161.3 2637 14.030N01 27.830E2010 08 0410 10 42145973.90.11962147.4 2737 05.390N00 52.280E2010 08 0415 47 02333101979.42164.6 2836 28.590N01 30.980W2010 08 0511 50 16146988.10.12132221.7 2938 38.330N10 23.378E2011 05 0202 38 21337472994.92224.4 3038 48.283N10 15.562E2011 05 0205 44 07337461986.80.12082183.5 3138 51.443N10 10.985E2011 05 0207 48 27337471980.22187.4 3239 46.437N11 53.155E2011 05 0402 55 20337470983.82206.7 3340 40.544N12 47.930°2012 08 0218 02 31337469980.32176.9 3440 40.524N12 47.925E2012 08 0218 04 25337466980.12156.8 SBE 911plus The same CTD always used since 2003 Several calibration per year Standard SeaBird routines for data processing 34 XBT and 29 CTD profiles ∆Time < 43’ ∆ Latitude < 0’.05 ∆ Longitude < 0’07 13 XBT weighted 18 XBT wire density measured 14 XBT calibrated in bath Distribution of max depth (only for profiles without problems): D < 2000 m = 2 2000 < D< 2200 m = 14 D > 2200 m = 7

8.  Cheng et al. (2011) original: 1.How to get FRE? (i). Calculate standard deviation (STD) of Txbt-Tctd in each time window (ii). Find A/B/Offset when total STD over all time windows is minimized. 2. Pure thermal bias ： Residuals after correcting depth error Cheng, L. J., Zhu, J., Reseghetti, F., Liu, Q. P., 2011: A new method to estimate the Systematical Biases of Expendable Bathythermograph, J. Atmos. Oceanic Technol., 28, 2, 244-265. FRE: D=At-Bt 2 -Offset XBT bias include Depth error +Pure thermal bias FRE – a Cheng et al.(2011) improvement Include a threshold: The first norm of the temperature gradient file in a depth window should be larger than 0.001 o C/m, so that there is a significant temperature variation in this window and the method will be able to capture the shape of a temperature profile. Use a Depth window (depending on depth) A test is included to determine the depth window In the original model, the depth window was set arbitrary. Ideally, the depth window should be chosen as the typical length scale of temperature variation with depths. In Mediterranean sea, the water Temperature is usually highly homogeneous below 300-400m depth: therefore, it is difficult to separate the scale of noises and signals. Identify (if possible) a technique useful for all kind of probes, independently on the length of profiles.

9. Test to determine the depth window 1. Change the size of depth window at each time. 2. Calculate the min(STD) by using Cheng et al.(2011) method in each depth window 3. Determine the size of depth window empirically. Depth Window: Less than 20m at upper 200m Depth Window: Larger than 50m at 1000-2000m Depth Window: 30-80m at 200- 1000m Depth window for T5: 0-200m: Depth window=4m 200-900m: Depth window=50m 900-2300m: Depth window=80m

10. T5 FRE coefficients vs. T water We separated the pairs (with long XBT profiles) to two groups: G1 with T>20 o C near the sea surface, and G2 with T<20 o C near the sea surface A < A_ Sippican (always, but less than 2 STD level) T5 falls quicker in warmer water than in colder water (difference at 1 STD level). Temp(>20°C), Weighted mean: A=6.7746 m/s (1*STD=0.0322) B=0.0014 m/s2 (1*STD=0.0006) Offset=1.6000m (1*STD=1.9533) Temp(<20°C), Weighted mean: A=6.7406 m/s (1*STD=0.0458), B=0.0015 m/s2 (1*STD=0.0003) Offset=2.3429m(1*STD=2.2322)

11. FRE à la Boyd&Linzell BL-model seems to be able to improve the depth representation in the deeper ocean BL model and A/B/Offset model shows almost identical results in the upper ocean. But BL model seems to better perform in the deeper part An example: T5_71070.edf vs. 200710c_0051.dat Depth=At-Bt 2 -Offset+Ct 3 Problem: BL model include one more variable C

12. T10 (preliminary, 6 probes  ) Good acquisition down to about 250m depth Used Depth-Window: 4m and 40m A=6.4148 ms -1 (1*STD=0.0462) B=0.0020 ms -2 (1*STD=0.0030) Offset=0.5333 m (1*STD=0.4719) A > A_ Sippican (6.301 m/s) at more than 2 STD B has a large variability Offset is small and marginally compatible with 0

13. Summary (for T5, mainly) Extended Acquisition: good values down to more than 2000m (and 250m)  no indication of anomalous behaviour  change Max Depth No-way for gradient profile analysis in the Med T-5: Indication on T water influence on A T-5: Height seems is influencing first 100m, better H > 2.5m T-5 FRE (preliminary): –A=6.7517ms -1 B=0.0013 ms -2 Offset=2.0857 m T-5: FRE with cubic term useful at great depth –A=6.7625ms -1 B=0.0016 ms -2 Offset=1.8485 m C=0.0000012 ms -3 TO DO Increase statistics Evaluate influence of H Dependance on T water, Bias due to Recording Systems Include calibration into profile analysis …(something new?) Add a sensor for the pressure Continue XBT monitoring (SOOP) (Why?)

14. 1999092020000927 20040913 20050915201209242013091920140925 That’s all, folks Thank you very much for your attention Acknowledgments D.Galletti - CMRE, La Spezia, Italy G.Goni - AOML/NOAA,Miami, USA S. Latorre – INFN, Milan, Italy the captains E.Gentile and V. Lubrano Lavadera and technicians of Italian RV Urania FR was partially funded by EU projects MyOcean/MyOcean2..