Time-Split versus Process-Split Coupling of Parameterizations and Dynamical Core

David L. Williamson National Center for Atmospheric Research, Boulder, Colorado

Search for other papers by David L. Williamson in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

Simulations are compared to determine the effect of the details of the coupling of the parameterization suite with the dynamical core on the simulated climate. Simulations based on time-split and process-split couplings are compared to a simulation with the original version of the NCAR Community Climate Model–3 (CCM3), which is a mixture of the two approaches. In the process-split coupling, the two components are based on the same state and their tendencies are added to produce the updated state. In the time-split coupling, the two components are calculated sequentially, each based on the state produced by the other. Overall the differences between simulations produced with the various coupling strategies are relatively small. Thus, with the time step used in the CCM3, the different time truncation errors introduced by the different coupling strategies have less effect on simulations than other arbitrary aspects of the model design. This does not imply that the time truncation errors are insignificant, just that they are similar in the cases examined here. There are, however, regions where the differences are statistically significant. The differences in the thermal balance are analyzed in these regions. The most notable differences occur between the time-split case and CCM3 over regions of Antarctica. In summer, although the temperature difference near the surface is modest, the balance of terms in the two cases is very different, with a difference in sign in the sensible heat flux between the two cases. In winter, the parameterization terms have a very strong grid-scale structure associated with parameterized clouds forming predominantly at a single grid level. The dynamics is unable to respond with a grid-scale structure. This draws into question whether the vertical resolution is adequate to properly model the physical processes.

Corresponding author address: Dr. David L. Williamson, NCAR/CGD, P.O. Box 3000, Boulder, CO 80307-3000. Email: wmson@ucar.edu

Abstract

Simulations are compared to determine the effect of the details of the coupling of the parameterization suite with the dynamical core on the simulated climate. Simulations based on time-split and process-split couplings are compared to a simulation with the original version of the NCAR Community Climate Model–3 (CCM3), which is a mixture of the two approaches. In the process-split coupling, the two components are based on the same state and their tendencies are added to produce the updated state. In the time-split coupling, the two components are calculated sequentially, each based on the state produced by the other. Overall the differences between simulations produced with the various coupling strategies are relatively small. Thus, with the time step used in the CCM3, the different time truncation errors introduced by the different coupling strategies have less effect on simulations than other arbitrary aspects of the model design. This does not imply that the time truncation errors are insignificant, just that they are similar in the cases examined here. There are, however, regions where the differences are statistically significant. The differences in the thermal balance are analyzed in these regions. The most notable differences occur between the time-split case and CCM3 over regions of Antarctica. In summer, although the temperature difference near the surface is modest, the balance of terms in the two cases is very different, with a difference in sign in the sensible heat flux between the two cases. In winter, the parameterization terms have a very strong grid-scale structure associated with parameterized clouds forming predominantly at a single grid level. The dynamics is unable to respond with a grid-scale structure. This draws into question whether the vertical resolution is adequate to properly model the physical processes.

Corresponding author address: Dr. David L. Williamson, NCAR/CGD, P.O. Box 3000, Boulder, CO 80307-3000. Email: wmson@ucar.edu

Save
  • Beljaars, A. C. M., 1991: Numerical schemes for parameterizations. Proc. ECMWF Seminar on Numerical Methods in Atmospheric Models, Vol. 2. Reading, United Kingdom, ECMWF, 1–42.

    • Search Google Scholar
    • Export Citation
  • 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, 150 pp.

    • Search Google Scholar
    • Export Citation
  • Caya, A., R. Laprise, and P. Zwack, 1998: Consequences of using the splitting method for implementing physical forcings in a semi-implicit semi-Lagrangian model. Mon. Wea. Rev., 126 , 17071713.

    • Search Google Scholar
    • Export Citation
  • Chen, M., and J. R. Bates, 1996: Forecast experiments with a global finite-difference semi-Lagrangian model. Mon. Wea. Rev., 124 , 19922007.

    • Search Google Scholar
    • Export Citation
  • Gates, W. L., Ed.,. 1995: Proc. First Int. AMIP Scientific Conf.,. Monterey, CA. WCRP Rep. WCRP-92, WMO/TD-732, 532 pp.

  • Gates, W. L., and Coauthors. 1999: An overview of the results of the Atmospheric Model Intercomparison Project (AMIP). Bull. Amer. Meteor. Soc., 80 , 2955.

    • Search Google Scholar
    • Export Citation
  • Hack, J. J., 1994: Parameterization of moist convection in the National Center for Atmospheric Research community climate model (CCM2). J. Geophys. Res., 99 , 55515568.

    • Search Google Scholar
    • Export Citation
  • Hack, J. J., . 1998: Sensitivity of the simulated climate to a diagnostic formulation for cloud liquid water. J. Climate, 11 , 14971515.

    • Search Google Scholar
    • Export Citation
  • Hack, J. J., J. T. Kiehl, and J. W. Hurrell, 1998: The hydrologic and thermodynamic structure of the NCAR CCM3. J. Climate, 11 , 11791206.

    • Search Google Scholar
    • Export Citation
  • Holtslag, A. A. M., and B. A. Boville, 1993: Local versus nonlocal boundary-layer diffusion in a global climate model. J. Climate, 6 , 18251842.

    • Search Google Scholar
    • Export Citation
  • 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, 11 , 12071236.

    • Search Google Scholar
    • Export Citation
  • 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.

    • Search Google Scholar
    • Export Citation
  • Kiehl, J. T., D. L. Williamson, and P. J. Rasch, 1998a: The National Center for Atmospheric Research Community Climate Model: CCM3. J. Climate, 11 , 11311149.

    • Search Google Scholar
    • Export Citation
  • Kiehl, J. T., and J. W. Hurrell, 1998b: The energy budget of the NCAR Community Climate Model: CCM3. J. Climate, 11 , 11511178.

  • Lenderink, G., and A. A. M. Holtslag, 2000: Evaluation of the kinetic energy approach for modeling turbulent fluxes in stratocumulus. Mon. Wea. Rev., 128 , 244258.

    • Search Google Scholar
    • Export Citation
  • Lin, S-J., 1997: A finite-volume integration method for computing pressure gradient force in general vertical coordinates. Quart. J. Roy. Meteor. Soc., 123 , 17491762.

    • Search Google Scholar
    • Export Citation
  • Lin, S-J., and R. B. Rood, 1997: An explicit flux-form semi-Lagrangian shallow-water model on the sphere. Quart. J. Roy. Meteor. Soc., 123 , 24772498.

    • Search Google Scholar
    • Export Citation
  • Murthy, A. S. V., and R. S. Nanjundiah, 2000: Time-splitting errors in the numerical integration of semilinear systems of ordinary differential equations. Mon. Wea. Rev., 128 , 39213926.

    • Search Google Scholar
    • Export Citation
  • Sportisse, B., 2000: An analysis of operator splitting techniques in the stiff case. J. Comput. Phys., 161 , 140168.

  • Staniforth, A., and A. Robert, 1981: The computational stability of certain schemes for incorporating vertical fluxes in semi-implicit baroclinic primitive equation models. Division Rech. Prévision Numérique (RPN) Tech. Note, 19 pp.

    • Search Google Scholar
    • Export Citation
  • Strang, G., 1968: On the construction and comparison of difference schemes. SIAM J. Numer. Anal., 5 , 506517.

  • Teixeira, J. P. D. C. C., 2000: Boundary layer clouds in large scale atmospheric models: Cloud schemes and numerical aspects. Ph.D. thesis, Faculdade de Ciências, Universidade de Lisboa, ECMWF, 190 pp.

    • Search Google Scholar
    • Export Citation
  • 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 , 407446.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 406 96 15
PDF Downloads 242 60 6