The Portable University Model of the Atmosphere (PUMA) is the dynamical core of the climate model PlanetSimulator [Fraedrich et al. 2005, Fraedrich 2012] and it is based on the multi-level spectral hydrostatic model described by Hoskins and Simmons (1975). Model fields are represented in terms of spherical harmonics subject to a triangular trunction and the spectral transform method enables an efficient calculation of nonlinear products [Orszag 1970 and Eliasen et. al 1970]. The model employs a semi-implicit time integration method for making the treatment fast gravity wave tendencies more efficient. The vertical coordinate is sigma (pressure divided by surface pressure) and the vertically discretized equations conserve total energy and mass.
PUMA uses spherical harmonics as basis functions. The truncation of the spectral representation is triangular at a maximum total wavenumber M (referred to as TM). The computational mode of the semi-implicit time integration scheme is damped by a Robert-Asselin filter using the filtering coefficient 0.02. 6th order hyperdiffusion prevents the emergence of Gibbs phenomena.
||# of horizontal
|Grid spacing at
the equator (km)
time step (s)
time step (s)
|Coefficient for 6th order hyperdiffusion
|T85||32768||156.4||240||240||6.209 x 1025|
|T170||131072||78.2||120||120||9.873 x 1024|
|T341||524288||39.1||120||120||2.447 x 1023|
|T682||2097152||19.55||60||60||1.536 x 1022|
PUMA computes nonlinear products on a Gaussian grid. The number of longitudes results from the formula 3M+1 where M denotes the total wavenumber at which triangular truncation takes place. The figure shows the gridpoints for a triangular truncation at total wavenumber 85 (T85).
Name of the DCMIP Modeling Mentor: PUMA will be featured as a remotely-participating model. The model experiments will be conducted by Thomas Frisius at the University of Hamburg, Germany.
DCMIP-2012: News Report on DCMIP
Check out the NCAR CISL News report http://www2.cisl.... More »
cjablono @ 09/20/2012 10:56 a.m.
DCMIP-2012: Photo Gallery
Check out the photos of the Saturday hike on the ... More »
cjablono @ 08/04/2012 5:12 p.m.
DCMIP-2012: Welcome & Ice Breaker Reception
Monday (7/30/2012) 4:30-6:30pm, NCAR Mesa Lab Tree Plaza More »
murphysj @ 07/27/2012 12:16 p.m.
DCMIP-2012: Pre-Workshop Informal Get-Together
Sunday (7/29/2012) at the Baker Street Pub & Grill near ... More »
murphysj @ 07/27/2012 12:13 p.m.