NCL > Application examples > Basic examples

ContourPlot example 5

Creating a map and contour overlay animation

This example can be created using HLU C library calls, HLU FORTRAN library calls, or NCL. It demonstrates how to read data from a netCDF file, set plot attributes, and generate a color-filled contour plot with a labelbar overlaid on a cylindrical equidistant map projection of the globe. The example also shows how to iteratively loop through the data and generate multiple plots to create an animation. The names of the example codes that create this plot are cn05c.c, cn05f.f, and cn05n.ncl.

View this animation.


This module discusses how to create the previous plot using HLU function calls and NCL. This module also shows how to read netCDF data from a file, create a scalar field data object, a workstation object for output to an NCGM workstation, a contour plot, a labelbar as an annotation object to a contour plot, and a MapPlot object. There is no resource file for this example, as all the resources are set in the source code.

Creating the plot using HLU C library calls

The HLU C program that generates this plot is called cn05c.c.

Creating the plot using HLU FORTRAN library calls

The HLU FORTRAN program that generates this plot is called cn05f.f.

Creating the plot using NCL

The NCL script that generates this plot is called cn05n.ncl.

The data

The data for this plot is from a netCDF file called meccatemp.cdf. The original data for this plot was generated by Warren Washington (NCAR) and Gerald Meehl (NCAR) for the Model Evaluation Consortium for Climate Assessment (MECCA) project. The MECCA Analysis Team at the Climate Impacts Centre in Sydney, Australia, prepared and archived the data, and previous visualizations of this data by Kendal McGuffie (University of Technology, Sydney) were referenced for selecting appropriate attributes for the plot and animation.

The data file contains a three-dimensional array of temperature data. The dimensions of the temperature variable (t) are time (31), lat (40), and lon (49).

The data file is located in your NCAR Graphics data directory in a subdirectory called "cdf". You can get the name of the data directory by typing "ncargpath data" at your shell prompt. If you have netCDF installed on your system, then you can change directory to where the netCDF file resides and type "ncdump -h meccatemp.cdf" to view the header information for this data file.

How to run this example

The examples are installed in the following locations:

  • $NCARG_ROOT/lib/ncarg/hluex/contourplot/cn05c.c
  • $NCARG_ROOT/lib/ncarg/hluex/contourplot/cn05f.f
  • $NCARG_ROOT/lib/ncarg/nclex/contourplot/cn05n.ncl
The netCDF data file is installed in the following location:

  • $NCARG_ROOT/lib/ncarg/data/cdf/meccatemp.cdf
You can copy this example and run it by typing "ng4ex cn05c", "ng4ex cn05f", or "ng4ex cn05n". A copy of the source file will be placed in your current working directory. The source code will be compiled and automatically run for you. You must have the netCDF library installed on your system in order to compile the C or FORTRAN version of this example.

You can view the output NCGM file using the NCAR Graphics ctrans utility. (For example, to view the file generated from cn05n.ncl, type "ctrans -d X11 cn05n.ncgm".)