© Crown copyright Met Office

An introduction to CDO, NCL and PRECIS utilities

Kuala Lumpur, Malaysia, 8th – 11th November 2012

© Crown copyright Met Office

What are they?

• CDO, NCL and PRECIS utilities are tools for data analysis and visualisation.

• Different tool are useful for different activities e.g. CDO and PRECIS tools for analysis and NCL for visualisation.

• In the worksheets these tools are used together to process, analyse and visualise PRECIS output.

© Crown copyright Met Office

PRECIS utilities

• Designed for use with PRECIS output (which is in Met Office PP format.)

• Can be used with Linux and Windows.

• Can be typed directly into the command line, or scripted.

• Extensive range of different utilities available, see http://www.metoffice.gov.uk/precis/tutorials

• For example – calculate the JJA mean:

ppstats –H “mon>=6 and mon<=8” –o jja.mean.pp –t mean infile.pp

© Crown copyright Met Office

CDO – Climate Data Operators (1)

• Developed by the Max Planck Institute for use with GRIB 1/2, netCDF 3/4, SERVICE, EXTRA and IEG data.

• Designed specifically for climate and NWP data analysis, there are more than 600 operators available.

• Can be run on Linux, Windows, MasOS and others.

• As with PP utilities can be typed directly into the command line, or scripted.

• For example – calculate the JJA mean:

cdo timmean –selmon,6/8 infile.nc jja.mean.nc

© Crown copyright Met Office

•Free to download and documentation and support forums can be found at https://code.zmaw.de/projects/cdo

CDO – Climate Data Operators (2)

© Crown copyright Met Office

NCL – NCAR Command Language (1)

• Developed by NCAR (Nation Center for Atmospheric Research) for use with GRIB 1/2, netCDF 3/4, shape files and ascii data.

• Free interpreted language designed for scientific data processing and visualization.

• Can be run on Linux, Windows, MasOS and others.

• Can be typed directly into the NCL command line (very time consuming), or scripted.

• Produces plots of publishable quality.

© Crown copyright Met Office

NCL – NCAR Command Language (2)

• Extensive documentation and hundreds of example scripts and plots at http://www.ncl.ucar.edu/index.shtml

© Crown copyright Met Office

NCL – NCAR Command Language (3)

• Looks more complex than it is.

© Crown copyright Met Office

Using tools together

• The worksheets combine all three of these tools to post process and analysis PRECIS data.

1. Use PP utilities to remove rim and convert from PP to netCDF format.

2. Use CDO to analyse the netCDF data.

3. Use NCL to visualise (and process) the data.

© Crown copyright Met Office

Worksheets

1 – File locations and pre-processing (into to Linux and using PP utilities.)

2a- Introduction to using CDO for analysis and NCL for visualisation (validation.)

2b- Creating future climate scenarios and analysing change (using CDO and NCL.)

3- Thresholds and extremes analysis (using CDO and NCL.)

© Crown copyright Met Office

Questions