YOKOSUKA YK17-E01 Expendable Bathythermograph (XBT) Fall-rate bias corrected

Last Modified: 2019-12-27
: YK17-E01
: Processed (DMO)-QCed
: Depth, Temperature

For Using Data

Data Management Office
See Terms and Conditions about constrain of use.
See Terms and Conditions about data citation.
Using XBT (eXpendable Bathy Thermograph) system, the vertical distribution of water temperature is observed during free fall of its probe part in the seawater. On board, the analogue signal is converted to the temperature by data processor and the data is stored in PC. Depth data is calculated from the elapsed time.

Fall-rate bias corrected data using new coefficients of Kizu et al. (2005) for all TSK T-5 probes.

Kizu et al. (2005): A New Fall-Rate Equation for T-5 Expendable Bathythermograph (XBT) by TSK. Journal of Oceanography, Vol. 61, pp. 115 to 121
(1) Launcher
Hand launcher
Manufacturer : Sippican,Inc.
Operation area : Rear upper deck

(2) Converter
Manufacturer : Tsurumi Seiki Co., LTD.
Location : Investigation room
Sampling rate : 50 msec

(3) XBT probe specifications
Probe Type TSK T-5 TSK T-6 TSK T-7 TSK T-10
Temperature range [deg-C] -2 to 35
Temperature accuracy [deg-C] +/- 0.2
Temperature resolution [deg-C] 0.01
Measurment depth [m] 1830 460 760 300
Depth accuracy [m] 5 or +/- 2% of depth; whichever is larger
Maximum elapsed time [sec] 291 73 123 48
Rated ship speed [knot] 6 15 15 10

Since XBT carries no pressure sensor, we need to estimate depth from the elapsed time. The fall-rate equation is as follows.

Z = at + 10E-3 * bt2

Where Z(m) is the depth and t(sec) is the elapsed time.

In addition, coefficients of the fall-rate equation are different by probe types.
The corrected data were calculated using new coefficients and elapsed time.
The elapsed time was calculated from the original depth which had been calculated by manufacture's coefficients.

Probe Type TSK T-5 (New Coefficients of Kizu et al.) TSK T-5 (Manufacture's Coefficients)
Coefficient-a 6.54071 6.828
Coefficient-b -1.8691 -1.82
The list of an XBT type used in each cast is as follows.

Cast name Probe Serial No. Probe Type Launcher Converter
BT-201712222126p - T-5 Hand MK-30N

(1) For sensor's stablility, values of less than 1 m for temperature are replaced by missing values, respectively, based on manufacturer's recommendation.

(2) Quality control
QCed data were added flag according to the NODC (National Oceanographic Data Center) quality control procedure.
1) The gradient check of adjacent depth data
2) The broad range check set up at given ocean space and depth
Please see the site of NODC of the following link for quality control procedure in detail.
In addition, an abnormal value is identified by a visual check, and the data after visual QC is released.
(1) It is reported that T-5 probes produced by Tsurumi Seiki Co. Ltd. (TSK T-5 probes) have a fall-rate bias. Please see the following about publication policy of XBT fall-rate bias correction data.
: YK17-E01
: Processed (DMO)-QCed
: Depth, Temperature

Observation Map

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  2. Then click the observation name, figures will be displayed.
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Data List

  File names
ex_read2.f (Sample Program)
Observation List
The list of observation is shown as follows.
Observation Time and Date Lat. [°] Lon. [°]
BT-201712222126p 2017-12-22 21:26 32.3489 144.8126
: YK17-E01
: Processed (DMO)-QCed


Each data file contains one line header (meta data) followed by data lines for each cast.
The number of data lines are recorded in the header.
  1. Header part
No. Column Content Format Remarks
1 1 Header ID a1 fixed as '#'
2 3 - 6 Data ID a4 XBT
3 8 - 22 Cruise ID a15
4 33 - 40 Date i8 YYYYMMDD (UTC)
5 42 - 45 Time i4 hhmm (UTC)
6 47 - 55 Latitude i2,a1,f5.2,a1 dd-mm.mmN(S)
7 57 - 66 Longitude i3,a1,f5.2,a1 ddd-mm.mmE(W)
8 68 - 71 Number of data lines i4
9 72 - 73 Terminator - CR+LF
  1. Data part
No. Column Content Unit Format Remarks
1 1 - 11 Depth m f11.1
2 12 - 22 Temperature deg-C f11.2 ITS-90
3 45 - 55 Flag - i11 1 - 7 : space
8 : flag of depth
9 : flag of temperature
10 - 11 : space
* reference : 'Definition of Quality Control Flags'
4 56 - 57 Terminator - - CR+LF
Each contents of the data part is stored in 11 bytes.
Missing value is presented by '-5', and error value is presented by '-9'.

Definition of Quality Control Flags
  1. Depth Flags
  2. 0 - accepted value
    1 - error in recorded depth ( same or less than previous depth )
    2 - density inversion

  3. Observed Level Flags
  4. N - missing value
    0 - accepted value
    1 - range outlier ( outside of broad range check )
    2 - failed inversion check
    3 - failed gradient check
    4 - zero anomaly
    5 - failed combined gradient and inversion checks
    6 - failed range and inversion checks
    7 - failed range and gradient checks
    8 - failed range and zero anomaly checks
    9 - failed range and combined gradient and inversion checks
    A - failed visual check

    * Range and gradient check is performed to XBT data.

QCed data were added flag according to the NODC (National Oceanographic Data Center) quality control procedure, additionally visually checked. Please see the site of NODC of the following link for quality control procedure.

Related Information

Update History

An observation data was registerd.