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Institute of Meteorology and Climatology, Leibniz Universität Hannover
Data visualizationlast update: 06. February 2020
Notes
Page 2PALM seminar 2020
Data visualizationOverview
▪ PALM produces NetCDF data output
▪ 3D
▪ xy-, xz-, yz-cross-sections
▪ profiles
▪ time series
▪ spectra
▪ Different tools can be used to visualize this data
▪ programming languages: NCL, python, R, …
▪ programs with GUI: ncview, Panoply, …
▪ NCL-based script delivered with PALM: palmplot
▪ → Python-based script will do the job soon: palmplot (under
construction, ready within the near future)
▪ Goal: get you started visualizing PALM data output and not
presenting the “perfect” tool for visualization
Notes
Page 3PALM seminar 2020
Data visualizationNetCDF Introduction
NetCDF: Network Common Data Format
▪ Developed by the University Corporation for Atmospheric Research
▪ Machine independent data format (open standard)
▪ Intended for array-oriented scientific data
▪ Data is self-describing (for explanation see
https://ops.aps.anl.gov/manuals/SDDStoolkit/SDDStoolkitse1.html):
▪ Header describes file layout, content and global attributes
▪ Metadata (information about the data which simplifies the
locating/archiving of it): Attributes like units or data types
▪ Library’s core is written in C and provides an API for C, C++, Fortran;
separate Implementation in Java
▪ Interfaces to netCDF are available in R, Perl, Python, Ruby, Haskell,
Mathemtica, MATLAB, IDL, Octave
▪ Supports parallel I/O (Parallel-NetCDF, HDF-5)
Notes
Page 4PALM seminar 2020
Data visualizationncview
Ncview - a simple first look:
▪ Start via command line:
ncview <filename>
▪ Select variable of interest
Hints and functions:
▪ x will always close application
▪ Left click to go forward, right click to go backwards (time, slices, …)
▪ Set Range: Cursor in input-field!
▪ Left click in plot to get line-plot
▪ Click again to add lines
▪ Click close to exit (not x)
Notes
Page 5PALM seminar 2020
Data visualizationncview
color map
animate
animation speed
interpolation on/off
magnify
change slice
always:
left click forward
right click backwards
Notes
Page 6PALM seminar 2020
Data visualizationPanoply
Panoply – a netCDF, HDF and GRIB Data Viewer
▪ Developed by NASA (https://www.giss.nasa.gov/tools/panoply/)
▪ Intuitive and easy access to content of data file
▪ Edit plot easily
▪ plot range/scale
▪ area
▪ labels
▪ Vertical profiles
▪ Create fairly presentable figures
▪ Export pictures and animations
Notes
Page 7PALM seminar 2020
Data visualizationPalmplot
palmplot
▪ Shell script delivered with palm (will be used during the seminar)
▪ Idea: Explicitly developed for PALM output to standardize/unify
visualization among the community
▪ Based on NCL (NCAR Command Language)
▪ Interpreted language (no compilation) designed for scientific data
processing
▪ Capable of data analysis and visualization
▪ Supports NetCDF3/4, GRIB 1/2, HDF4/5, ASCII, binary, etc. ▪ Execution: ncl script.ncl
▪ Get it here: www.ncl.ucar.edu/Download/
▪ Find the NCL scripts atpalm/current_version/trunk/SCRIPTS/NCL
▪ Find the documentation at
https://palm.muk.uni-hannover.de/trac/wiki/doc/app/ncl▪ due to stopped development of NCL: new, python-based palmplot
coming in near future
Notes
Page 8PALM seminar 2020
Data visualizationPalmplot
Creating the palmplot command line:
palmplot <plot_identifier> file_1=<file> format_out=<format>
file_out=<file>
▪ Execute command in JOBS/<run_name>/OUTPUT
▪ Possible options for <plot_identifier>:
<plot_identifier> data set used ncl script (.ncl)
xy xy or 3D cross_sections
xz xz or 3D cross_sections
yz yz or 3D cross_sections
pr profile or 3D profiles
ts time series timeseries
sp spectra spectra
Notes
Page 9PALM seminar 2020
Data visualizationPalmplot
Creating the palmplot command line:
palmplot <plot_identifier> file_1=<file> format_out=<format>
file_out=<file>
▪ A short introduction to palmplot is given by typing: palmplot ?
▪ List of available parameters:
https://palm.muk.uni-hannover.de/trac/wiki/doc/app/nclparlist
▪ Available parameters differ for the different <plot_identifier>s
Don't worry: For the exercise sessions, your advisors will provide you with the required palmplot commands!
Notes
Page 10PALM seminar 2020
Data visualization
PALM online:
https://palm.muk.uni-hannover.de
Our YouTube channel:
youtube.com/user/palmhannover
The end
Notes