Postprocessing with IDL

In addition to the NCL scripts some IDL routines exist for handling and analyzing netCDF datasets generated by PALM. IDL (Interactive Data Language) is a programming language developed especially for analyzing and visualizing scientific data. Further information on IDL can be found ​here.

IDL is not free. To run the here presented programs you must have a fully functional licensed version of IDL. To get IDL please ​contact the IDL producers via web.

Once IDL is installed, the presented IDL programs can be executed. There exist different modes running IDL programs. To run the presented IDL programs we recommend to do the following:

• Use an editor like kate to adapt the code to your needs (usually only some variables have to be changed in the head of the program)
• Type 'idl' at your terminal (console) to start the command line version of IDL (only available on UNIX/LINUX platforms)
• Type '.run programname' and press <Enter>, where 'programname' is the name of your IDL program (usual ending is '.pro')

The IDL program will be executed.

IDL programs

The presented IDL programs can be used without making larger changes in the code. Usually only a few changes in the head of the program like path to the netCDF file, desired variable or e.g. desired point in time are necessary. The head of the program is framed with the symbol '#'. Additionally there are some annotations in the code (lines, that start with ';') for a better understanding. For downloading the IDL programs click on the symbol on the right of the program name. The following IDL programs are available:

1. check_palm_output.pro​

This program checks the content of a netCDF file and displays number of contained variables, namelist of variables, dimensions of variables, type of variables (e.g float) and units of variables on your terminal (console).

2. plot_ts_palm_output.pro​

Output are plots of time series for variables turbulent kinetic energy, max. wind velocity, friction velocity and convective velocity scale.

3. plot_pr_palm_output.pro​

Similar to the time series program, but for profile data. Variables are three components of wind velocity, potential temperature, vertical turbulent heat flux, turbulent flux of momentum, turbulent kinetic energy and variances of resolved wind components and potential temperature. The sub-grid fraction of the turbulent heat flux can be added in the plot of turbulent heat flux. You can select z-axis in meters or normalized coordinates (normalized by height of minimum of turbulent heat flux).

4. plot_xz_palm_output.pro​

A further program plotting 2-dimensional contours of xz cross section data.

Note

These programs are a minimal set for handling PALM datasets. For further and special issues you need more and/or other programs. Rename the files and modify or enlarge the code for your needs. Treat these programs as a basis for analyzing and visualizing PALM output data using IDL. In case of problems, comments or suggestions please contact Florian Herbort.