ncar command language

Building Analysis andVisualization Infrastructure for

the Geosciences

Mary Haley

Computing in Atmospheric Sciences 2001Annecy, France

Tuesday, 30 October 2001

Scientific Computing DivisionNational Center for Atmospheric Research

NCAR Command Language

• Introduction to NCL• Brief history of NCL• CCSM-NCL collaboration• Other projects• Future directions


Introduction to NCL• A scripting language designed for the analysis

and visualization of data• Powerful in 3 areas:

– File input and output– Data processing– Graphics

• Based on netCDF model• Runs on many UNIX systems (Compaq, IBM,

PC/Linux, PC/Windows, SGI, Sun)• Free to the public


Brief history of NCLNCAR GraphicsDesign and development

1960s – 1990sJune 1991

First version released August 1995CCSM-NCL collaboration January 1997First “climate-enhanced” version released

August 1998

Second “C.E.” version released

May 1999

NCL free to public November 2000


CCSM-NCL collaboration• What is the CCSM?• Requirements for CCSM post-processor• NCL’s role• Support for CCSM-NCL users• Contributions and examples from

climate community• If I say “CSM”, I mean “CCSM”.


What is the CCSM?• A fully-coupled, global climate model

that provides state-of-the-art computer simulations of the earth’s past, present, and future climate states.


Requirements for the CCSMpost-processor

• Read/write certain portable data formats (netCDF, HDF, HDF-EOS)

• Read GRIB• Built-in climate analysis functions• Interface w/user Fortran/C codes and

external libraries (i.e. IMSL)• Generate different types of graphics in

publication-quality formats


NCL’s role:file input and output

BEFORE• Read/write netCDF,

HDF, ASCII, binary• Read GRIB• Functions for

querying input files

AFTER• Read GRIB files

containing ECMWF complex coefficients

• Read CCM history tape files

• Read multiple files with one statement


NCL’s role:data processing

BEFORE• Over 100 routines• Standard math

calculations• Handle missing data• Access Fortran & C

routines

AFTER• Over 400 routines• Spherical harmonics• Scalar and vector

regridding• 1, 2, 3D interpolations• Script to simplify

Fortran/C routine access


• Sea level pressure computation• Spectral/cross-spectral analysis• Geopotential height computation for

CCM hybrid coordinates• Empirical orthogonal functions, singular

value decomposition• Other non-CCSM specific functions

NCL’s role:data processing (cont’d)


NCL’s role:graphics

BEFORE• Objected-oriented

interface• Contours, XY plots,

vectors, streamlines, maps

• Flexibility via hundreds of resources

AFTER• Suite of plotting

templates• Highly-stylized• Takes advantage of

meta data


Support for CCSM-NCL users• Documentation• CCSM Support Network web site • Consulting• NCL workshops• ncl-talk email list


Contributions from users

• Over 100 functions– zonal averages– climatologies– interannual variability– specialized plotting scripts– wave number spectra– diagnostics package


Real world examples• Matthew Huber, Danish Center for Earth System

Science• Joel Norris, Scripps Institute of Oceanography• Adam Phillips, Dennis Shea, Mark Stevens, CGD• Bjorn Stevens, UCLA• Greg Thompson, Research Applications Program


AMWG diagnostics package• Written completely in NCL• Produces over 475 postscript plots and

tables in a variety of formats from CCSM monthly netCDF files

• Used to compare two CCSM model simulations or a model simulation to observational and reanalysis data


Other current projects• Weather Research and Forecast Model • Community Data Portal• High resolution maps• Other ports


WRF Model• Next-generation mesoscale forecast model• NCL’s role

– multi-model comparison– real-time weather forecasting plots– horizontal and vertical cross sections– skew-T plots– convert WRF data to vis5D data


Community Data Portal• Data Server Pilot Projects

– Live Access Server (LAS)– Distributed Oceanographic Data System –

(DODS)– NCL acts as middleware– DSS Reanalysis II is one such project– Other data portals in the works (Regional

Climate Data Access System, Vegetation and Ecosystem modeling/analysis)


Future directions• Mesoscale Model (MM5) - terrain-following

sigma-coordinate model designed to simulate or predict mesoscale and regional-scale atmospheric circulation (Penn State, NCAR)

• Earth System Grid - virtual collaborative environment that links distributed centers, users, models, and data. Sponsored by DOE Office of Science, involves 5 laboratories and one university


RANGS/GSHHS Coastline Database

• GSHHS (Global Self-consistent Hierarchical High-Resolution Coastlines), created by Paul Wessel and Walter Smith.

• RANGS (Regionally Accessible Nested Global Shorelines), created by Rainer Feistel.– Expressed to 0.000001 degrees of lat/lon (about 0.1

meters).– Actual accuracy is more like 500 meters.– Points in database are about 300 meters apart.


Future directions (cont’d)• New functionality in NCL

– Curvilinear coordinates– HDF 5– More robust 3D capability

- Vis5D, a visualization system for large 5-D gridded data sets such as those produced by numerical weather models

– Other ports (Mac OSX)


URLS• NCL Home Page

http://ngwww.ucar.edu/ncl/

• CCSM Support Networkhttp://www.cgd.ucar.edu/csm/support/

• Me ([email protected])

http://ngwww.ucar.edu/ncl/

http://www.cgd.ucar.edu/csm/support/

National Center for Atmospheric Research

Boulder, ColoradoUnited States

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