The sensitivity of a general circulation model climate to the moisture transport formulation

The sensitivity of the climate of the NCAR Community Climate Model to the numerical method used to transport water vapor is described. We compare two versions of the model, one of which uses a spectral method and the other a shape-preserving semi-Lagrangian method for the water vapor transport. These methods are very different in terms of their computational properties and produce very different climatologies in model simulations. These differences in climate result primarily from the redistribution of water vapor in the model. The redistribution carries with it differences in convection and cloud distributions and the associated radiative heating, which in turn affects the model climate. We interpret the differences using a sensitivity study perspective. Some of the changes produced by changing from spectral to semi-Lagrangian transport are beneficial (that is, the model climate is closer to observations), and some are detrimental. We believe that many of the detrimental changes may be explained in terms of prior tuning of the physical parameterizations to the “spectral climatology” and may also be due to inadequate or missing physics. We examine many of the pertinent feedback loops and diagnose the processes associated with the changed climate.

[1]  P. Rasch,et al.  Computational aspects of moisture transport in global models of the atmosphere , 1990 .

[2]  A. Slingo,et al.  Sensitivity of the Earth's radiation budget to changes in low clouds , 1990, Nature.

[3]  Veerabhadran Ramanathan,et al.  The role of earth radiation budget studies in climate and general , 1987 .

[4]  David L. Williamson,et al.  Semi-Lagrangian moisture transport in the NMC spectral model , 1990 .

[5]  A. Slingo,et al.  The response of a general circulation model to cloud longwave radiative forcing. I: Introduction and initial experiments , 1988 .

[6]  J. Kiehl,et al.  Dependence of cloud amount on horizontal resolution in the National Center for Atmospheric Research community climate model , 1991 .

[7]  J. Peixoto,et al.  The Atmospheric Branch Of The Hydrological Cycle And Climate , 1983 .

[8]  Philip J. Rasch,et al.  On Shape-Preserving Interpolation and Semi-Lagrangian Transport , 1990, SIAM J. Sci. Comput..

[9]  Kevin E. Trenberth,et al.  Global atmospheric mass, surface pressure, and water vapor variations , 1987 .

[10]  L. Williamson,et al.  Description of NCAR Community Climate Model (CCM0B) , 1983 .

[11]  Eric J. Pitcher,et al.  The Response of a Spectral General Circulation Model to Refinements in Radiative Processes , 1983 .

[12]  S. Manabe,et al.  SIMULATED CLIMATOLOGY OF A GENERAL CIRCULATION MODEL WITH A HYDROLOGIC CYCLE , 1965 .

[13]  Lawrence L. Takacs.  Effects of using a posteriori methods for the conservation of integral invariants. [for weather forecasting] , 1988 .

[14]  Veerabhadran Ramanathan,et al.  Comparison of cloud forcing derived from the Earth Radiation Budget Experiment with that simulated by the NCAR Community Climate Model , 1990 .

[15]  Application of a Semi-Lagrangian Integration Scheme to the Moisture Equation in a Regional Forecast Model , 1985 .

[16]  H. Kreiss,et al.  Comparison of accurate methods for the integration of hyperbolic equations , 1972 .

[17]  S. Williamson,et al.  Modifications and Enhancements to the NCAR Community Climate Model (CCM1) , 1989 .

[18]  P. Rasch,et al.  Two-dimensional semi-Lagrangian trans-port with shape-preserving interpolation , 1989 .

[19]  Norman A. McFarlane,et al.  The Effect of Orographically Excited Gravity Wave Drag on the General Circulation of the Lower Stratosphere and Troposphere , 1987 .

[20]  Y. Sasaki.  Variational design of finite-difference schemes for initial value problems with an integral invariant , 1976 .

[21]  B. Barkstrom,et al.  Cloud-Radiative Forcing and Climate: Results from the Earth Radiation Budget Experiment , 1989, Science.