Gosac Analysis Package

One mesure of our understanding of ocean circulation and biochemistry
is our ability to simulate the ocean behaviour with ocean models. To
mesure such ability, an ocean modeler must rely on some type of analysis
package. Different institutions rely on different analysis packages make
difficult to compare model results. Furthermore modelers often waste time
building analysis tools that already exist elsewhere.

GAP is a package of analysis tools that was designed to help compare
output from different ocean models.

The strengths of GAP include

its ability to exploit standard netCDF GDT data files (e.g. those

within the OCMIP model output database);

its facility to compare model output to data;
its ability to easily produce maps and sections of output from

multiple models, each on its original grid;

its ability to animate model results;
its high quality output;
its potential for expandability.

GAP was developed because few existing analysis packages were
designed for the needs of model comparison. We are aware of only one
VCS developed by PCMDI. Unfortunately even VCS was designed for
comparison of atmospheric models, which have structured rectilinear
grids. Ocean models can have more complex grids (e.g. curvilinear,
finite elements) which complicates their analysis. Interpolation to a
regular grid is possible but not appropriate as a required first step for
model comparison.
Ocean models are developed with considerable forethought concerning
grid structure and resolution. Interpolation always result in loss of detail
and no one grid is satisfactory for interpolation of all ocean models.

Overview

GAP is a distribution of custom built modules for the powerful software
Tecplot (http://www.amtec.com). Those modules are called AddOns.
They were developed in C and integrated to Tecplot to increase its
functionnality and offer to researchers a powerful environment to analyse
and compare oceanic model ouptut.
As many oceanic models have been defined with complex discretisation
and geographical description, classic softwares cannot represent easily
model output. By its functionnalities (zoom, annotation, layout, postscript
paper ouput...), its capacities to work with complex finite elements data
and added with dedicated AddOns, Tecplot is a good tool to elaborate
answers on projects such as intercomparison of model ouput.

The GAP AddOns are essentially resumed by the following actions:

Read the input file at the netCDF format and GDT conventions
Compute calculations (projection, slice, connexion network...)
Stuff values into Tecplot memory
Apply style

ScreenShots and Key Features

Images and movies of some key features of GAP.

Documentation

Mapper Maps on any depth surface
Tracker Get cruise track or define your own
Slicer Make section of any tracer along a cruise track

AnimateTime Animate time series of a map or a section
AnimateTime MultiFiles Animate time series across multiple files
AnimateDepth Animate with depth

Movies with Macro Command Language

ZoneMean
ZonalMean
Plotter

Installation Guide

Follow this guide and install GAP in few steps.

Create a new reference grid file

Understand how geographic informations of the model is found by GAP
through a netcdf associate file called reference grid file.

Interaction with Ferret

How to work with GAP and Ferret?

How to plot your model with Ferret?

Using Ferret to produce maps.

What is next ?

See what will be the next steps in the GAP development.

FAQ

Frequently asked questions.

Suggestions and bug reports

If you found a bug in the GAP addons or wish to suggest some
improvements, send me an email brock@lsce.saclay.cea.fr.

Author: Patrick Brockmann
Date: 06/10/2000