How to use Ferret External Function for writing Vis5D files

Below is an annotated version of the script ef_wv5d_demo.jnl

! ef_wv5d_demo.jnl (9/98)

! Description:examples of the external function to write Vis5D files
from FERRET.

! SYNTAX:
! The first argument to the GO script is the file name.
! Arguments 2 through 9 are variable names to be written.
! For example:

! Use External Functions to write climatology data to a Vis5D file.

! By default Vis5D looks for variables named U and V to plot as
! horizontal winds (Hwind1) so it is convenient to name them this way.

The script vis5d_write.jnl calls the external function to write the file named by the first argument.

   LET u =  uwnd
   LET v =  vwnd 
 
   GO vis5d_write coads_clim.v5d sst airt wspd u v slp

The script vis5d_start.jnl runs Vis5D from within Ferret.

  GO vis5d_start coads_clim.v5

Write COADS climatology and Levitus climatology data to a Vis5D file. Use the horizontal grid from coads_climatology, and a regularly-spaced depth grid in the upper 500 meters of the ocean. When writing data to a Vis5D file from more than one data set, you must regrid the data so that the horizontal grid and the time axes are the same. The vertical axis, or layers as they are called in Vis5D, can be different for different variables.

   CAN REGION
   USE coads_climatology, levitus_climatology
   SET REGION/X=180:280/Y=5:45
 
   DEFINE AXIS/Z=0:500:50/DEPTH dep500 
   DEFINE GRID/LIKE=sst[d=coads_climatology]/Z=dep500 cl_grid

The Levitus data has one time step; apply the 1:1@AVE so that the time axes of both variables are defined as time-averaged.

   LET sst_tav = sst[D=coads_climatology, G=cl_grid, l=1:12@AVE]
   LET lev_tmp = temp[D=levitus_climatology, G=cl_grid, l=1:1@AVE]
 
   GO vis5d_write coads_levitus_test.v5d lev_tmp sst_tav

A Vis5D utility appends a Vis5D file to an existing file. It is called by the GO script vis5d_append.jnl, which allows us to add more time steps to a Vis5D file. The spatial grid for the file being appended must match the grid of the original file. The utility checks this and will issue an error message if they do not match.

We will write a few months' data from the COADS Climatology surface data set, and then append data from later in the year. Times being appended need to be after times in the initial file, but we can skip time steps between the two files. If some variables are not available for the appended set, the file is written and Vis5D will display the variables when they are present.

   USE coads_climatology
   LET u =  uwnd
   LET v =  vwnd

   SET REGION/l=1:4
   GO vis5d_write coads_suv.v5d sst u v

   CAN REGION
   SET REGION/l=7:12
   GO vis5d_append coads_suv.v5d sst

   GO vis5d_start coads_suv.v5d

Links for getting started learning Vis5D:

 
oar.pmel.contact_ferret@noaa.gov 

5 Apr, 1999