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Application of corrections to original XBT data

Temperature bias correction:

Tcorr=T0-Toff    (1)
Where T0 is the observed XBT temperature and Toff is the thermal offset

For Deep XBTs [Deep defined as where depth of XBT is deeper than 500m]:
Tcorr=T0-ToffD

For Shallow XBTs [Shallow defined as where depth of XBT is shallower than 500m]:
Tcorr=T0-ToffS

For Western Pacific [north of 20oS and west of 180oE]:
Tcorr=T0-ToffWP

The thermal bias for the Western Pacific remains the same for both the shallow and deep XBTs.
ToffS, ToffD, ToffWP vary with year. Values are found in Table 1. Values vary based on year of XBT drop.

Depth bias correction:

Zcorr=Z0(1-B-AZ0)-Zoff    (2)
Where Z0 is the observed XBT depth and Zoff is the depth offset.

The values of A,B, and Zoff vary based on year of XBT deployment, depth of the XBT deployed and the temperature of the water column to which it is deployed. The depth correction equation for each case is provided below.

Based on the temperature that the XBTs are deployed, they are classified as low temperature class (the mean of the vertically averaged temperature of the water column between 0-200m is colder than 10oC) and high temperature class (the vertically averaged temperature of the water column between 0-200m is warmer than 10oC).

Depth bias correction for deep XBTs deployed in low temperature class:
Zcorr=Z0(1-BDL-ADLZ0)-ZoffDL

Depth bias correction for deep XBTs deployed in high temperature class:
Zcorr=Z0(1-BSH-ASHZ0)-ZoffDH

ADL, BDL, ZoffDL, ADH, BDH, ZoffDH values are presented in Table 2.

Depth bias correction for shallow XBTs deployed in low temperature class:
Zcorr=Z0(1-BSL-ASLZ0)-ZoffSL

Depth bias correction for shallow XBTs deployed in high temperature class:
Zcorr=Z0(1-BSH-ASHZ0)-ZoffSH

ASL, BSL, ZoffSL , ASH, BSH, ZoffSH values are presented in Table 3.

The depth bias correction for shallow and deep XBTs for the Western Pacific are presented in Table 4 for the years 1968 to 1985 and the depth correction is given by

Zcorr=Z0(1-BSWP-ASWPZ0)-ZoffSWP
Zcorr=Z0(1-BDWP-ADWPZ0)-ZoffDWP


  Last modified:    Thu, 23-Apr-2015 19:57 UTC NCEI.info@noaa.gov
 
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