NATSUSHIMA NT09-11 Expendable Bathythermograph (XBT) Fall-rate bias corrected

Last Modified: 2017-07-07
: NT09-11
: Processed (DMO)-QCed
: JAMSTEC
: Depth, Temperature
:
OCEANS > OCEAN TEMPERATURE > WATER TEMPERATURE

For Using Data

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Instrument:
XBT
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 (a=6.54071, b=-1.8691) of Kizu et al. (2005) for all TSK T-5 probes.

Fall-rate equation of XBT takes following form,
Z = at + 10E-3 * bt2
where Z(t) is the depth (in meters) at an elapsed time since probe hit water surface t (in seconds). This equation has two constant coefficients, a and b.

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.

[Reference]
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.
Type : LM-3A
Operation area : Rear upper deck

(2) Converter
Manufacturer : Tsurumi Seiki Co., LTD.
Type : MK-130
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] -2.22 to 35.55
Temperature accuracy [deg-C] +/- 0.2
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
Coefficient-a 6.828 6.691 6.691 6.301
Coefficient-b -1.82 -2.25 -2.25 -2.16
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 * bt^2

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

In addition, coefficients of the fall-rate equation are different by XBT types.

Probe type TSK T-5 TSK T-6 TSK T-7 TSK T-10
Coefficient-a 6.828 6.691 6.691 6.301
Coefficient-b -1.82 -2.25 -2.25 -2.16
* Coefficients listed above are supplied by Sippican, Inc., in USA.

The list of an XBT type used in each cast is as follows.

Cast name XBT type
BT-026220090727T-5
BT-026420090729T-5


(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 fall-rate bias corrected data.
: NT09-11
: Processed (DMO)-QCed
: JAMSTEC
: Depth, Temperature
:
OCEANS > OCEAN TEMPERATURE > WATER TEMPERATURE

Observation Map

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Figures

Data List

File names
BT-026220090727p.dat
BT-026420090729p.dat
ex_read2.f (Sample Program)
Observation List
The list of observation is shown as follows.
Observation Time and Date Lat. [°] Lon. [°]
BT-026220090727p 2009-07-27 20:58 27.7855 126.8951
BT-026420090729p 2009-07-29 00:13 24.8740 123.8565
: NT09-11
: Processed (DMO)-QCed
: JAMSTEC

XBT DMO

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

Cruise Data Dive Data
: HYPER-DOLPHIN

Update History

2017-07-07
An observation data was registerd.
2014-09-04
An observation data was registerd.
2014-04-01
An observation data was registerd.
2012-09-28
An observation data was registerd.