Vertical velocity computation package
This page provides a simple package to compute vertical velocities from a known density field and a known geostrophic field. The scientific background, based on the Omega equation can be found for example in:
Units are 'kg/m3' for density, 'm/s' for horizontal geostrophic velocity. Results for vertical velocity are provided in m/day.
The following package contains the omega source code and a test example.omega.tar.gz
To install the source, download the file, uncompress the file with'gunzip omega.tar.gz'
and extract the files with'tar xvf omega.tar'
If your computer does not know 'tar' or 'gunzip', try the following package omega.zip
and uncompress it with'unzip omega.zip'
The single source file 'omega.f' contains the computation routines Compile it with the following command:'f77 -O omega.f -o omega.a'
File 'omega' is a korn shell script. It pipes every information to the omega code.The files 'alboran.sal.*' and 'alboran.tem.*' in the directory 'data' are the data files (example of the survey 1 of the Omega-1 cruise).
To run the computation, simply type'omega'
The resulting file 'omega.W' should be equal (or very close) to file 'omega.W.compare'. The result at level 26 (101m depth) should look like the postscript file'omega.ps'
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'.
Output loops are nested as follows: DO K=1,NZ DO J=1,NY WRITE(55,541) (W(I,J,K),I=1,NX) ENDDO ENDDO 541 FORMAT(8F10.5) 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. Of course, you are free to write your own I/O routines: just mind the computation format.
Last modified March 5th, 1999
Send comments to M.Rixen@ulg.ac.be