• Boer, G. J., and Coauthors, 1992: Some results from an intercomparison of the climates simulated by 14 atmospheric general circulation models. J. Geophys. Res.,97, 12771–12786.

  • Bonan, G. B., 1996: A land surface model (LSM version 1.0) for ecological, hydrological, and atmospheric studies: Technical description and user’s guide. NCAR Tech. Note NCAR/TN-417+STR. National Center for Atmospheric Research, Boulder, CO, 150 pp.

  • Chen, M., and J. R. Bates, 1996: A comparison of climate simulations from a semi-Lagrangian and an Eulerian GCM. J. Climate,9, 1126–1149.

  • Côté, J., and A. Staniforth, 1988: A two-time-level semi-Lagrangian semi-implicit scheme for spectral models. Mon. Wea. Rev.,116, 2003–2012.

  • Feichter, J., E. Kjellström, H. Rodhe, F. Dentener, J. Lelieveld, and G.-J. Roelofs, 1996: Simulation of the tropospheric sulfur cycle in a global climate model. Atmos. Environ.,30, 1693–1707.

  • Hack, J. J., 1994: Parameterization of moist convection in the National Center for Atmospheric Research community climate model (CCM2). J. Geophys. Res.,99, 5551–5568.

  • ——, B. A. Boville, B. P. Briegleb, J. T. Kiehl, P. J. Rasch, and D. L. Williamson, 1993: Description of the NCAR Community Climate Model (CCM2). NCAR Tech. Note NCAR/TN-382+STR, 108 pp.

  • ——, J. T. Kiehl, and J. W. Hurrell, 1998: The hydrologic and thermodynamic structure of the NCAR CCM3. J. Climate, in press.

  • Held, I. M., and M. J. Suarez, 1994: A proposal for the intercomparison of the dynamical cores of atmospheric general circulation models. Bull. Amer. Meteor. Soc.,75, 1825–1830.

  • Hurrell, J. W., J. J. Hack, B. A. Boville, D. L. Williamson, and J. T. Kiehl, 1998: The dynamical simulation of the NCAR CCM3. J. Climate, in press.

  • Kiehl, J. T., J. J. Hack, G. B. Bonan, B. A. Boville, B. P. Briegleb, D. L. Williamson, and P. J. Rasch, 1996: Description of the NCAR Community Climate Model (CCM3). NCAR Tech. Note NCAR/TN-420+STR, 152 pp.

  • ——, ——, ——, ——, D. L. Williamson, and P. J. Rasch, 1998a: The National Center for Atmospheric Research Community Climate Model: CCM3. J. Climate, in press.

  • ——, J. J. Hack, and J. W. Hurrell, 1998b: The energy budget of the NCAR Community Climate Model: CCM3. J. Climate, in press.

  • Mote, P. W., K. H. Rosenlof, J. R. Holton, R. S. Harwood, and J. W. Waters, 1995: Seasonal variations of water vapor in the tropical lower stratosphere. Geophys. Res. Lett.,22, 1093–1096.

  • ——, ——, and Coauthors, 1996: An atmospheric tape recorder: The imprint of tropical tropopause temperatures on stratospheric water vapor. J. Geophys. Res.,101, 3989–4006.

  • Phillips, T. J., 1994: A summary documentation of the AMIP models. PCMDI Rep. 18, 343 pp.

  • Rasch, P. J., and D. L. Williamson, 1990: On shape-preserving interpolation and semi-Lagrangian transport. SIAM J. Sci. Stat. Comput.,11, 656–687.

  • Ritchie, H., and C. Beaudoin, 1994: Approximations and sensitivity experiments with a baroclinic semi-Lagrangian spectral model. Mon. Wea. Rev.,122, 2391–2399.

  • ——, and M. Tanguay, 1996: A comparison of spatially averaged Eulerian and semi-Lagrangian treatments of mountains. Mon. Wea. Rev.,124, 167–181.

  • ——, C. Temperton, A. Simmons, M. Hortal, T. Davies, D. Dent, and M. Hamrud, 1995: Implementation of the semi-Lagrangian method in a high-resolution version of the ECMWF forecast model. Mon. Wea. Rev.,123, 489–514.

  • Rivest, C., A. Staniforth, and A. Robert, 1994: Spurious resonant response of semi-Lagrangian discretizations to orographic forcing: Diagnosis and solution. Mon. Wea. Rev.,122, 366–376.

  • Staniforth, A., and J. Côté, 1991: Semi-Lagrangian integration schemes for atmospheric models—A review. Mon. Wea. Rev.,119, 2206–2223.

  • Williamson, D. L., 1997: Climate simulations with a spectral, semi-Lagrangian model with linear grids. Numerical Methods in Atmospheric and Oceanic Modeling. The André J. Robert Memorial Volume, C. Lin, R. Laprise, and H. Ritchie, Eds., 279–292.

  • ——, and P. J. Rasch, 1989: Two-dimensional semi-Lagrangian transport with shape-preserving interpolation. Mon. Wea. Rev.,117, 102–129.

  • ——, and J. G. Olson, 1994: Climate simulations with a semi-Lagrangian version of the NCAR Community Climate Model. Mon. Wea. Rev.,122, 1594–1610.

  • ——, and P. J. Rasch, 1994: Water vapor transport in the NCAR CCM2. Tellus,46A, 34–51.

  • Zhang, G. J., and N. A. McFarlane, 1995: Sensitivity of climate simulations to the parameterization of cumulus convection in the Canadian Climate Centre general circulation model. Atmos.–Ocean,33, 407–446.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 32 32 5
PDF Downloads 25 25 4

A Comparison of Semi-Lagrangian and Eulerian Tropical Climate Simulations

View More View Less
  • 1 National Center for Atmospheric Research, * Boulder, Colorado
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

At the modest vertical resolutions typical of climate models, simulations produced by models based on semi-Lagrangian approximations tend to develop a colder tropical tropopause than matching simulations from models with Eulerian approximations, all other components of the model being the same. The authors examine the source of this relative cold bias in the context of the NCAR CCM3 and show that it is primarily due to insufficient vertical resolution in the standard 18-level model, which has 3-km spacing near the tropopause. The difference is first diagnosed with the Held and Suarez idealized forcing to eliminate the complex radiative–convective feedback that affects the tropopause formation in the complete model. In the Held and Suarez case, the tropical simulations converge as the vertical grid layers are halved to produce 36 layers and halved again to produce 72 layers. The semi-Lagrangian approximations require extra resolution above the original 18 to capture the converged tropical tropopause. The Eulerian approximations also need the increased resolution to capture the single-level tropopause implied by the 36- and 72-level simulations, although with 18 layers it does not produce a colder tropopause, just a thicker multilevel tropopause. The authors establish a minimal grid of around 25 levels needed to capture the structure of the converged simulation with the Held and Suarez forcing. The additional resolution is added between 200 and 50 mb, giving a grid spacing of about 1.3 km near the tropopause. With this grid the semi-Lagrangian and Eulerian approximations also create the same tropical structure in the complete model. With both approximations the convective parameterization is better behaved with the extra upper-tropospheric resolution. A benefit to both approximations of the additional vertical resolution is a reduction of the tropical temperature bias compared to the NCEP reanalysis. The authors also show that the Eulerian approximations are prone to stationary grid-scale noise if the vertical grid is not carefully defined. The semi-Lagrangian shows no indication of stationary vertical-grid-scale noise. In addition, the Eulerian simulation exhibits significantly greater transient vertical-grid-scale noise than the semi-Lagrangian.

* The National Center for Atmospheric Research is sponsored by the National Science Foundation.

Corresponding author address: Dr. David L. Williamson, NCAR, P.O. Box 3000, Climate and Global Dynamics Division, Boulder, CO 80307-3000.

Email: wmson@ucar.edu

Abstract

At the modest vertical resolutions typical of climate models, simulations produced by models based on semi-Lagrangian approximations tend to develop a colder tropical tropopause than matching simulations from models with Eulerian approximations, all other components of the model being the same. The authors examine the source of this relative cold bias in the context of the NCAR CCM3 and show that it is primarily due to insufficient vertical resolution in the standard 18-level model, which has 3-km spacing near the tropopause. The difference is first diagnosed with the Held and Suarez idealized forcing to eliminate the complex radiative–convective feedback that affects the tropopause formation in the complete model. In the Held and Suarez case, the tropical simulations converge as the vertical grid layers are halved to produce 36 layers and halved again to produce 72 layers. The semi-Lagrangian approximations require extra resolution above the original 18 to capture the converged tropical tropopause. The Eulerian approximations also need the increased resolution to capture the single-level tropopause implied by the 36- and 72-level simulations, although with 18 layers it does not produce a colder tropopause, just a thicker multilevel tropopause. The authors establish a minimal grid of around 25 levels needed to capture the structure of the converged simulation with the Held and Suarez forcing. The additional resolution is added between 200 and 50 mb, giving a grid spacing of about 1.3 km near the tropopause. With this grid the semi-Lagrangian and Eulerian approximations also create the same tropical structure in the complete model. With both approximations the convective parameterization is better behaved with the extra upper-tropospheric resolution. A benefit to both approximations of the additional vertical resolution is a reduction of the tropical temperature bias compared to the NCEP reanalysis. The authors also show that the Eulerian approximations are prone to stationary grid-scale noise if the vertical grid is not carefully defined. The semi-Lagrangian shows no indication of stationary vertical-grid-scale noise. In addition, the Eulerian simulation exhibits significantly greater transient vertical-grid-scale noise than the semi-Lagrangian.

* The National Center for Atmospheric Research is sponsored by the National Science Foundation.

Corresponding author address: Dr. David L. Williamson, NCAR, P.O. Box 3000, Climate and Global Dynamics Division, Boulder, CO 80307-3000.

Email: wmson@ucar.edu

Save