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High-frequency noise and depth error associated with the XCTD/XBT profiles in the Indian Ocean sector of Southern Ocean and southwestern tropical Indian Ocean

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Abstract

Despite the advent of towing conductivity, temperature and depth (CTD) sensors, expendable bathythermographs (XBTs) and expendable CTDs (XCTDs) are still employed as an easy and effective means to collect temperature profiles in the ocean from a moving ship. Since these expendable probes do not have any pressure sensor, it infers depth from the time elapsed from the moment the probe touches the water using a fall rate equation (FRE). Previous studies have highlighted that the wrong FRE can lead to depth biases and affect XBT/XCTD temperature data quality. The XBT–XCTD–CTD comparison tests carried out in the Indian sector of the Southern Ocean (SO) and south-western tropical Indian Ocean (SWTIO) were used to assess high-frequency noise and depth biases present in these expendable probes. Power spectral density (PSD) analysis of XCTD temperature profiles showed that spectral spikes are present at frequencies of 5 and 10 Hz, irrespective of the data-acquisition system (DAS) used. XBT profiles collected using an MK-150 DAS were also contaminated by high-frequency noise. Implementation of a running mean filter of suitable length effectively removed this high-frequency noise. Both in SO and SWTIO, XCTDs underestimated the depth (negative depth error) compared to the collocated CTD, indicating faster fall rates than those specified by the manufacturer. XBTs overestimated the depth (positive depth error) in SWTIO and SO. The depth error analyses suggested the regional temperature dependence of fall rates consistent with the previous CTD–XCTD/XBT comparison studies and attested the probe-to-probe variations in the fall rate. The intercomparison of different types of XCTDs and XBTs (viz., XCTD-3, XCTD-1 and XBT-T7) showed that XCTD-1 has the most stable fall rates, probably because of the ring hood structure present in the XCTD-1 probes.

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References

  • Abraham J P, Gorman J M, Reseghetti F, Minkowycz W J and Sparrow E M 2012 Turbulent and transitional modeling of drag on oceanographic measurement devices; Modell. Simul. Eng. 8 567864.

    Google Scholar 

  • Bailey R, Gronel A, Philips H, Meyers G and Tanner E 1994 CSIRO cookbook for quality control of expendable bathythermograph (XBT) data; CSIRO Mar. Lab. Rep. 221 75.

    Google Scholar 

  • Beatty W H III, Bruce J G and Guthrie R C 1981 Circulation and oceanographic properties in the Somali basin as observed during the 1979 southwest monsoon; Naval Oceanogr. Off. Tech. Rep. 258 156.

    Google Scholar 

  • Boyer T, Gopalakrishna V V, Franco R, Naik A, Suneel V, Ravichandran M, Mohammed Ali N P, Mohammed Rafeeq M M and Anthony Chico R 2011 Investigation of XBT and XCTD biases in the Arabian Sea and the Bay of Bengal with implications for climate studies; J. Atmos. Oceanic Technol. 28 266–286.

    Article  Google Scholar 

  • Cheng L, Luo H, Boyer T, Cowley R, Abraham J, Gouretski V, Abraham J, Gouretski V, Reseghetti F and Zhu J 2018 How well can we correct systematic errors in historical XBT data?; J. Atmos. Oceanic Technol. 35 1103–1125, https://doi.org/10.1175/JTECH-D-17-0122.

    Article  Google Scholar 

  • Cowley R, Susan W, Lijing C, Tim B and Shoichi K 2013 Biases in expendable bathythermograph data: A new view based on historical side-by-side comparisons; J. Atmos. Oceanic Technol. 30 1195–1225.

    Article  Google Scholar 

  • Cunningham S A 2000 RRS Discovery Cruise 242, 07 Sep-06 Oct 1999. Atlantic–Norwegian exchanges. Southampton Oceanography Centre Cruise, Rep. 28.

  • DiNezio P N and Gustavo J G 2010 Identifying and estimating biases between XBT and Argo observations using satellite altimetry; J. Atmos. Oceanic Technol. 27(1) 226–240.

    Article  Google Scholar 

  • DiNezio P N and Gustavo Goni J 2011 Direct evidence of a changing fall-rate bias in XBTs manufactured during 1986–2008; J. Atmos. Oceanic Technol. 28 1569–1578.

    Article  Google Scholar 

  • Frants M, Damerell G M, Gille S T, Heywood K J, MacKinnon J and Sprintall J 2013 An assessment of density-based fine-scale methods for estimating diapycnal diffusivity in the Southern Ocean; J. Atmos. Oceanic Technol. 30 2647–2661, https://doi.org/10.1175/JTECH-D-12-00241.1.

    Article  Google Scholar 

  • Gargett A and Garner T 2008 Determining Thorpe scales from ship-lowered CTD density profiles; J. Atmos. Oceanic Technol. 25 1657–1670.

    Article  Google Scholar 

  • Gille Sarah T, Aaron L, Janet S, Gordon S and Richard S 2009 Anomalous spiking in spectra of XCTD temperature profiles; J. Atmos. Oceanic Technol. 26 1157–1164.

    Article  Google Scholar 

  • Goes M, Gustavo G and Klaus K 2013 Reducing biases in XBT measurements by including discrete information from pressure switches; J. Atmos. Oceanic Technol. 30 810–824.

    Article  Google Scholar 

  • Goni G et al. 2009 The ship of opportunity program; In: Proceedings of oceanObs’09. Sustained ocean observations and information for society; Vol. 2, Venice, Italy, 21–25 September 2009.

  • Goni G, Sprintall J, Bringas F, Cheng L, Cirano M, Dong S et al. 2019 More than 50 years of successful continuous temperature section measurements by the global eXpendable BathyThermograph (XBT) network, its integrability, societal benefits and future; Front. Mar. Sci. 6 452, https://doi.org/10.3389/fmars.2019.00452.

    Article  Google Scholar 

  • Gouretski V and Reseghetti F 2010 On depth and temperature biases in bathythermograph data. Development of a new correction scheme based on analysis of a global ocean database; Deep-Sea Res. I 57 812–833, https://doi.org/10.1016/j.dsr.2010.03.011.

    Article  Google Scholar 

  • Green A 1983 Bulk dynamics of the expendable bathythermograph; Deep-Sea Res. 31 415–426.

    Article  Google Scholar 

  • Hanawa K, Rual P, Bailey R, Sy A and Szabados M 1995 A new depth-time equation for Sippican or TSK T-7, T-6 and T-4 expendable bathythermographs (XBT); Deep-Sea Res. 42 1423–1451.

    Article  Google Scholar 

  • Hutchinson K A, Swart S, Ansorge I J and Goni G J 2013 Exposing XBT bias in the Atlantic sector of the Southern Ocean; Deep-Sea Res. I 80 11–22.

    Article  Google Scholar 

  • Ishii M and Kimoto M 2009 Reevaluation of historical ocean heat content variations with time-varying XBT and MBT depth bias corrections; J. Oceanogr. 65 287–299.

    Article  Google Scholar 

  • Johnson Gregory C 1995 Revised XCTD fall-rate equation coefficients from CTD data; J. Atmos. Oceanic Technol. 12 1367–1373.

    Article  Google Scholar 

  • Kizu S, Onishi H, Suga T, Hanawa K, Watanabe T and Iwamiya H 2008 Evaluation of the fall rates of the present and developmental XCTDs; Deep-Sea Res. I 55 571–586.

    Article  Google Scholar 

  • Kizu S, Sukigara C and Hanawa K 2011 Comparison of the fall rate and structure of recent T-7 XBT manufactured by Sippican and TSK; Ocean Sci. Discuss. 7 1811–1847.

    Google Scholar 

  • Kizu S, Yoritaka T and Hanawa K 2005 A new fall-rate equation for T-5 expendable bathythermograph (XBT) by TSK; J. Oceanogr. 61 115–121.

    Article  Google Scholar 

  • Luis A J and Lotlikar V 2021 Hydrographic characteristics along two XCTD sections between Africa and Antarctica during austral summer 2018; Polar Sci. 100705.

  • Ravichandran M 2011 In-situ ocean observing system; Operational Oceanography in the 21st Century, 55.

  • Reseghetti F, Borghini M and Manzella G M R 2007 Factors affecting the quality of XBT data results of analyses on profiles from the western Mediterranean Sea; Ocean Sci. 3 59–75.

    Article  Google Scholar 

  • Reverdin Marin G, Bourlès F B and L’Herminier P 2009 XBT temperature errors during French research cruise (1999–2007); J. Atmos. Oceanic Technol. 26 2462–2473.

    Article  Google Scholar 

  • Rintoul S R, Meredith M P, Schofield O and Newman L 2012 The Southern Ocean observing system; Oceanography 25 68–69.

    Article  Google Scholar 

  • Sloyan B M, Talley L D, Chereskin T K, Fine R and Holte J 2010 Antarctic intermediate water and Subantarctic mode water formation in the southeast Pacific: The role of turbulent mixing; J. Phys. Oceanogr. 40 1558–1574.

    Article  Google Scholar 

  • Stark J, Gorman J, Hennessey M, Reseghetti F, Willis J, Lyman J, Abraham J and Borghini M 2011 A computational method for determining XBT depths; Ocean Sci. 7 733–743.

    Article  Google Scholar 

  • Thadathil P, Saran A K, Gopalakrishna V V, Vethamony P and Araligidad N 2002 XBT fall rate in waters of extreme temperature. A case study in the Antarctic Ocean; J. Atmos. Oceanic Technol. 19 391–396.

    Article  Google Scholar 

  • Thompson A F, Gille S T, MacKinnon J A and Sprintall J 2007 Spatial and temporal patterns of small-scale mixing in Drake Passage; J. Phys. Oceanogr. 37 572–592.

    Article  Google Scholar 

  • Uchida H, Koji S and Takeshi K 2011 A method for data processing to obtain high-quality XCTD data; J. Atmos. Oceanic Technol. 28 816–826.

    Article  Google Scholar 

  • Wijffels S, Willis E J, Domingues C M, Barker P, White N J, Gronell A, Ridgway K and Church J A 2008 Changing expendable bathythermograph fall rates and their impact on estimates of thermosteric sea level rise; J. Clim. 21 5657–5672.

    Article  Google Scholar 

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Acknowledgements

This study was supported by the Ministry of Earth Sciences, Government of India. We are thankful to Dr M Ravichandran, Director, NCPOR for his constant support. We are grateful to all the technicians, researchers and crew members of ORV Sagar Nidhi involved in the Indian expedition to SO and SWTIO from 2009 to 2012. This is NCPOR contribution number J-67/2021-22.

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Authors and Affiliations

  1. National Centre for Polar and Ocean Research, Ministry of Earth Sciences, Vasco da Gama, India

    Jenson V George & N Anilkumar

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  1. Jenson V George
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  2. N Anilkumar
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JVG: Data collection, analysis and draft preparation. NA: Conceptualisation, draft correction and editing.

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Correspondence to Jenson V George.

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Communicated by C Gnanaseelan

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George, J.V., Anilkumar, N. High-frequency noise and depth error associated with the XCTD/XBT profiles in the Indian Ocean sector of Southern Ocean and southwestern tropical Indian Ocean. J Earth Syst Sci 131, 47 (2022). https://doi.org/10.1007/s12040-021-01789-7

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  • DOI: https://doi.org/10.1007/s12040-021-01789-7

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