Convergence of aqua-planet simulations with increasing resolution in the Community Atmospheric Model, Version 3

The convergence of simulations from the Community Atmosphere Model with increasing resolution is determined in an aqua-planet context. Convergence as a function of scale is considered. Horizontal resolution (T42–T340) and time step (40–5 min) are varied separately. The simulations are sensitive to both. Global averages do not necessarily converge with increasing resolution. The zonal average equatorial precipitation shows a strong sensitivity to time step. Parametrizations should be applied in a range of time steps where such sensitivity is not seen. The larger scales of the zonal average equatorial precipitation converge with increasing resolution. There is a mass shift from polar to equatorial regions with increasing resolution with no indication of convergence. The zonal average cloud fraction decreases with increasing resolution with no indication of convergence. Equatorial wave propagation characteristics converge with increasing resolution, however a relatively high truncation of T170 is required to capture wavenumbers less than 16. Extremes are studied in the form of the probability density functions of precipitation. The largest half of the scales of the model converge for resolutions above T85.

[1]  D. Williamson.  Convergence of atmospheric simulations with increasing horizontal resolution and fixed forcing scales , 1999 .

[2]  B. Hoskins,et al.  Believable scales and parameterizations in a spectral transform model , 1997 .

[3]  Francis X. Giraldo,et al.  A Scalable Spectral Element Eulerian Atmospheric Model (SEE-AM) for NWP: Dynamical Core Tests , 2004 .

[4]  Matthew C. Wheeler,et al.  Convectively Coupled Equatorial Waves: Analysis of Clouds and Temperature in the Wavenumber–Frequency Domain , 1999 .

[5]  D. Williamson,et al.  A baroclinic instability test case for atmospheric model dynamical cores , 2006 .

[6]  W. Collins,et al.  The Formulation and Atmospheric Simulation of the Community Atmosphere Model Version 3 (CAM3) , 2006 .

[7]  Byron A. Boville,et al.  Sensitivity of Simulated Climate to Model Resolution , 1991 .

[8]  Reply to comment by B. A. Cash et al. on “On the presence of annular variability in an aquaplanet model” , 2007 .

[9]  On the presence of annular variability in an aquaplanet model , 2005 .

[10]  W. Spotz,et al.  A semi-Lagrangian double Fourier method for the shallow water equations on the sphere , 2003 .

[11]  Francis X. Giraldo,et al.  A spectral element semi-Lagrangian (SESL) method for the spherical shallow water equations , 2003 .

[12]  W. Collins,et al.  Description of the NCAR Community Atmosphere Model (CAM 3.0) , 2004 .

[13]  Luis Kornblueh,et al.  Sensitivity of Simulated Climate to Horizontal and Vertical Resolution in the ECHAM5 Atmosphere Model , 2006 .

[14]  James J. Hack,et al.  CCSM–CAM3 Climate Simulation Sensitivity to Changes in Horizontal Resolution , 2006 .

[15]  Christiane Jablonowski,et al.  A baroclinic wave test case for dynamical cores of general circulation models: Model intercomparisons , 2006 .

[16]  W. Collins,et al.  The Community Climate System Model Version 3 (CCSM3) , 2006 .

[17]  Richard Neale,et al.  A standard test for AGCMs including their physical parametrizations: I: the proposal , 2000 .

[18]  P. Swarztrauber,et al.  A standard test set for numerical approximations to the shallow water equations in spherical geometry , 1992 .

[19]  R. Stratton.  A high resolution AMIP integration using the Hadley Centre model HadAM2b , 1999 .

[20]  Stephen J. Thomas,et al.  A Discontinuous Galerkin Transport Scheme on the Cubed Sphere , 2005 .

[21]  V. Pope,et al.  The processes governing horizontal resolution sensitivity in a climate model , 2002 .

[22]  D. Williamson,et al.  Dependence of aqua‐planet simulations on time step , 2003 .

[23]  David L. Williamson,et al.  Evaluating Parameterizations in General Circulation Models: Climate Simulation Meets Weather Prediction , 2004 .

[24]  Comment on “On the presence of annular variability in an aquaplanet model” by Masahiro Watanabe , 2007 .

[25]  K. Ghia,et al.  Editorial Policy Statement on the Control of Numerical Accuracy , 1986 .