Curriculum Vitae

People at NCAR: Peter Hjort Lauritzen

The National Center for Atmospheric Research (NCAR) announces

Workshop on Transport Schemes on the Sphere

March 30 - 31, 2011, NCAR Mesa Lab, Boulder, Colorado, U.S.A.

Local Organizers are

Peter H. Lauritzen and William (Bill) Skamarock


  • The NCAR NESL divisions CGD and MMM as well as NCAR's IMAGe invite transport scheme developers to attend this "working" workshop on tracer transport schemes on the sphere. Participants are asked to give a presentation explaining the details of their transport scheme(s) and to present results from simulations using a newly developed test case suite for two-dimensional tracer transport on the sphere.

Overall goals

  • Better understand the characteristics of different transport schemes
  • Assess effective resolutions (for linear problems) with and without limiters/filters
  • Discuss how to estimate accuracy versus computational cost (with and without limiters/filters)
  • Investigate how well schemes maintain non-linear pre-existing functional relations

Test case setup

  • Active participants are asked to bring solutions to one of the challenging test cases described in Nair and Lauritzen (2010)
  • The test cases are easy to setup and formulated in terms of analytical winds and initial conditions:
    • 1 wind field: Non-divergent but highly deformational (Case 4 in Nair and Lauritzen, 2010)
    • 1 initial condition for air density: Unity everywhere
    • 4 initial conditions for tracer mixing ratio: Gaussian hills (smooth), cosine bells (quasi-smooth), slotted cylinders (non-smooth) and `correlated' cosine bells.
    • The wind field `reverses' half way through the simulation (t=T/2) so that the exact solution at the end of the simulation (t=T) is the initial condition. To avoid potential cancellation of errors by the flow reversal, a constant background flow is `added' to the time-reversing deformational flow.
    • Example animation of mixing ratio using slotted-cylinder initial conditions: movie
  • A summary of simulations we ask modelers to perform is given in the table below:

    Initial condition (IC) Resolutions Output Purpose
    Gaussian hills Range from 3° to 0.2° Standard error norms (t=T) Assess numerical convergence rate for smooth IC without and with limiters/filters
    Cosine hills Range from 3° to 0.2° Standard error norms (t=T) Assess numerical convergence rate for quasi-smooth IC and define effective resolution N
    Slotted cylinders 1.5°, 0.75°, N Standard error norms (t=T) and contour plots (t=T/2,t=T) Assess performance of scheme with `rough' IC without and with limiters/filters
    Cosine hills and correlated cosine hills 1.5°, 0.75°, N Mixing diagnostics and scatter plot at t=T/2 Assess ability of scheme to preserve nonlinear pre-existing functional relation without and with limiters/filters

  • More details and specific guidance on the test case setup are given here:

    Peter H. Lauritzen, William B. Skamarock, Michael J. Prather and Mark A. Taylor, 2012: A standard test case suite for two-dimensional linear transport on the sphere Geosci. Model Dev.: Vol. 5, pp. 887-901, DOI:10.5194/gmd-5-887-2012. [abstract], PDF (3.6MB)


  • Fortran90 module for computing mixing diagnostics and filament preservation diagnostic: diag.f90 (updated May 10, 2012)
  • Gnuplot script to make convergence plot and perform least-squares linear regression to estimate numerical order of convergence: conv.gp, sample error-norm data file (updated August 25, 2011)
  • NCL script for contour plots which assumes the data is in ASCII format on a regular latitude-longitude grid: plot.ncl; sample data
  • Gnuplot script to make scatter plot: corr.gp, sample data file and mixing bounds datafile
  • "tarball" of the Gnuplot script and data used to make the filament preservation diagnostic Figures: lf.tgz (August 23, 2011)


  • Registration fee: None
  • Abstract deadline: December 31, 2010 (please send a brief abstract describing your transport scheme to "tracer at cgd.ucar.edu").
  • Notification of acceptance : January 15, 2011
  • Hotel information: Best Western Golden Buff lodge (1725 28th St.)
  • Transportation: Shuttle transportation from the hotel to the Mesa Laboratory (and vice versa) for registered participants will be provided in the morning and afternoon on each day of the workshop.


  • Agenda with links to presentations (last updated April 6)

More information

  • Please contact Peter Hjort Lauritzen: pel at ucar dot edu



Personal home page of Peter Hjort Lauritzen

Last updated: 7-September-2011
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