T/S and W Analysis

 

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3D T/S, geostrophic horizontal and quasi-geostrophic vertical velocity fields

 

 

1. Introduction

This page provides access to the T/S, horizontal geostrophic velocity fields and quasi-geostrophic vertical velocity fields reconstructed from the omega BIO-hesperides cruise. The resulting 3D analysed fields (temperature, salinity and velocity) are stored as 3D matrices.

(up to Table of Contents)

2. Analysed Data Fields

There are three consecutive survey from the BIO Hesperides Cruise:

  1. Survey 1: 01/10/96 - 04/10/96
  2. Survey 2: 06/10/96 - 08/10/96
  3. Survey 1: 09/10/96 - 11/10/96

The T,S fields were computed by a variational inverse method and calibrated by a cross-validation procedure. The geostrophic velocities were obtained by integrating the thermal wind equation with a reference level of 200m, and adding a non-divergent stream function computed from ADCP data at that level. The vertical velocities were computed from the quasi-geostrophic omega formulation.

Units are 'psu' for salinity, 'degree Celsius' for temperature and 'm/s' for horizontal geostrophic velocity. Vertical velocity unit is m/day.

To get pseudo-synoptic analysed fields, several methods have been developped and implemented

  1. A relocation procedure to obtain pseudo-synoptic data was applied to the different surveys to check the synopticity of the data set. We successively apply analysis and relocation with geostrophic velocities until the fields converge, i.e when we obtain a mutual adjustment between T,S and velocity fields. The data are relocated to a reference sampling time, i.e. the middle of the concerned survey.

    (see

    Michel Rixen, 1997
    Data analysis and assimilation in the Alboran Sea: Computing synoptic T,S fields by relocating data points University of Liège, 89 pp.

    for more details )
  2.  

    As the successive surveys are very similar, linear interpolation in time was also tested. Field and sampling time analysis are used to allow a linear interpolation to a reference sampling time. Schematically:

    Quadratic interpolation is performed in the same way using the three consecutive surveys.

  3.  

    Finally, by weighting appropriately the data in the analysis, one may also obtain pseudo-synoptic data analyses. Data closer to the reference sampling time have higher weights.

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3. Format description

To understand the way the data is stored, please refer to the figure below. The file are stored in a 3D array (matrix) with 3 indexes I, J, K, going from 1 to IMAX, 1 to JMAX, 1 to KMAX. The origin is located at the 'bottom left deepest corner'.



There are KMAX horizontal slices from the bottom (K=1) to the surface (K=KMAX). Increasing I's go from W to E and increasing J's go from S to N.

The point (i,j,k) is located at (-5.0 + i*0.03 , i=0,43) long , (35.7 + j*0.025 , j=0,28) lat and (-301+k*8, k=0,37) m depth except for vertical velocities where point (i,j,k) is located at (-4.94 + i*0.03 , i=0,39) long , (35.75 + j*0.025 , j=0,24) lat and (-301+k*8, k=0,37) m depth.

Extracting routine written in FORTRAN :

 
C ----------------------------------------
      SUBROUTINE READIT (A,IMAX,JMAX,KMAX)
C ----------------------------------------

      REAL*4 A(IMAX,JMAX,KMAX)
      INTEGER IMAX,JMAX,KMAX

      DO 10 K = 1,KMAX
      DO 20 J = 1,JMAX

         READ (10,101) (A(I,J,K),I=1,IMAX)

20    CONTINUE
10    CONTINUE

101   FORMAT (5E12.5)

      END
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4. Access to the 3D analysed fields

To download the files, put a '.Z' after the file name. Uncompress the files with 'uncompress < filename >'.
  1. Survey 1

    •  Temperature raw
    •  Salinity    raw
    •  UV velocity raw
    •  W velocity  raw
  2. Survey 2

    •  Temperature raw
    •  Salinity    raw
    •  UV velocity raw
    •  W velocity  raw
  3. Survey 3

    •  Temperature raw
    •  Salinity    raw
    •  UV velocity raw
    •  W velocity  raw
(up to Table of Contents)
  1. Survey 1

  2. Survey 2

  3. Survey 3

(up to Table of Contents)
  1. Survey 12 (linear interpolation)

  2. Survey 23 (linear interpolation)

  3. Survey 123 (quadratic interpolation)

  4. Survey 123 (time correlation analysis)

(up to Table of Contents)

5. Access to the jpg images

  1. Survey 1

    •  Temperature raw
    •  Salinity    raw
    •  UV velocity raw
    •  W velocity  raw
  2. Survey 2

    •  Temperature raw
    •  Salinity    raw
    •  UV velocity raw
    •  W velocity  raw
  3. Survey 3

    •  Temperature raw
    •  Salinity    raw
    •  UV velocity raw
    •  W velocity  raw
(up to Table of Contents)
  1. Survey 1

  2. Survey 2

  3. Survey 3

(up to Table of Contents)
  1. Survey 12 (linear interpolation)

  2. Survey 23 (linear interpolation)

  3. Survey 123 (quadratic interpolation)

  4. Survey 123 (time correlation analysis)

Last modified October 26, 1998
Send comments to M.Rixen@ulg.ac.be

 

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