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The Next-Generation Flexible Global Atmospheric Model

The Next-Generation Flexible Global Atmospheric Model. Hann-Ming Henry Juang Environmental Modeling Center, NCEP Dynamics group: lead by H.-L. Pan M. Iredell, H. Juang, S. Moorthi, J. Sela Mentor: Don Johnson Symposium on the 50th Anniversary of Operational Numerical Weather Prediction

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The Next-Generation Flexible Global Atmospheric Model

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  1. The Next-Generation Flexible Global Atmospheric Model Hann-Ming Henry Juang Environmental Modeling Center, NCEP Dynamics group: lead by H.-L. Pan M. Iredell, H. Juang, S. Moorthi, J. Sela Mentor: Don Johnson Symposium on the 50th Anniversary of Operational Numerical Weather Prediction June 17, 2004

  2. Introduction • Reasons to develop new code • Flexible to test different dynamical cores • Develop to work with others, e.g. ESMF • Contents • Current design for flexibility • Current accomplishment • Immediate next steps • Future concerns

  3. Rules of Code Design • Fortran 90 modules, libraries built. • C preprocessor for compiling options • NAMELIST for running-time dimension • Data structure for generalization • Pluggable physics packages • Possibly pluggable dynamics • ESMF-type for super-structure • Easy to maintain and friendly to use

  4. Concept of Code Structure Super structure APIs Model layers APIs APIs : official ESMF; local ESMF; WRF API etc.

  5. Element of Super Structure preprocessing package execution postprocessing

  6. initial_prep (read namelist, allocation) initial_input (read input and data etc) atmos_initial initial_post (constant initialized) (allocate temporary spaces) model_prep atmos atmos_model model_integrate Model_post (deallocate temporary spaces) (prepare data for output) final_prep (write output or restart data) atmos_final final_output final_post (deallocation)

  7. integrate_init ( prepare coefficients ) integrate_radiationpre (integrate_getgrid) integrate_radiation integrate_dynamicpre (integrate_getgrid) integrate_dynamics model_integrate - (integrate_getwave) integrate_dynamicsadj integrate_physicspre (integrate_getgrid) integrate_physics (integrate_getwave) integrate_physicsadj integrate_fine ( updating, time-filter etc)

  8. dynamics_hybrid ( compute all values related to vertical coordinates etc ) integrate_dynamics - dynamics_nonadv ( compute all forcing except 3d advection ) dynamics_advect ( Eulerian or Lagrangian )

  9. atmos_initial atmos2ocean_initial ocean_initial ocean2atmos_initial atmos_model atmos2ocean_trans atmos_ocean - ocean_model ocean2atmos_trans ocean2atmos_final ocean_final atmos2ocean_final atmos_final

  10. Data Connection Variable structured data Structured Data Definition structured data Pass structured data, not by common block.

  11. Generalized Variable Structure type atmos_dynamics_vars_type real*DYN_KIND, pointer :: valu(:,:,:) character*5 , pointer :: name(:) integer , pointer :: indx(:) integer len,lev, stp, num endtype atmos_dynamics_vars_type

  12. Variable Definition type atmos_dynamics_defs_type character datatype*4 integer , pointer :: date(:) real fhour real , pointer :: dx(:) real , pointer :: dy(:) real , pointer :: ds(:) real , pointer :: sl(:) real , pointer :: si(:) integer numx,numy,nums integer numtracer,numdate,numwave endtype atmos_dynamics_defs_type

  13. Running-time Dimension • Pass dimension and options through NAMELIST as &ATMOS_DEFINE datatype=’coef', wavenumber=64, layernumber=28, longitudenumber=108, latitudenumber=1, initialtime=0., finaltime=240., timestep=1800., filter=0.92, &END

  14. Current Accomplishment • Implement all designs • Implement current operational dynamics and physics • Testing in three different platforms: ibm-sp, origin-o2k, pc-linux • Stable up to monthly integrations • Single and multiple tasks

  15. Model Grid • Spectral model with spherical transform is suitable for spherical domain. • Reduce Gaussian grid (Williamson and Rosinski, 2000) • Reduce spherical transform (Juang 2004) • Reduce Gaussian grid • Reduce Legendre computation

  16. Reduced (color) Full (black) Reduced - Full

  17. Hybrid Parallel Computing • Code structure is the same for single and multi PE s • Only IO and spectral transform routine contain MPI related calls • 2D decomposition with 1D option • 2D can run more PE s • 1D is faster in vector machine • Multi-threads for outmost do-loop • Consider vector in inner do-loop • For different # of PEs without recompiling

  18. 24-h accumulated rainfall from FGM Contour intervals of 4x10-4 m

  19. Next Steps • Generalized vertical coordinates • Implemented a generalized coordinates • Emphasized on sigma-theta coordinates • Current variables: U, V, T, P, and tracers • Comparisons forecast skills • Differences between sigma-p to sigma-theta • Differences from the operational one

  20. Hydrostatic system in generalized vertical coordinates

  21. P=0 q->infinite z=0 Isentropic dz/dt=0 P=P(q) z=qs/q P=Pq0 q=q0 sigma P=A(z)Pq0+B(z)Ps P=Ps z=1

  22. Future Concerns • Improve Dynamics as well as Physics • Un-approximated primitive equation • Higher resolution physics • Improve Numerical Methods • Optimal between conservation and accuracy • Adopt multi-dynamical cores • Linkage to other components of earth models through ESMF

  23. Model Equation • Nearly all global models are • Hydrostatic system • Diagnosis vertical momentum • Shallow-atmosphere assumption • Next generation could be years later • Very high resolution is expected • Hydrostatic is not valid • Full Coriolis effect • Deep atmosphere

  24. Momentum Equation

  25. Un-approximated Approach • From energy point of view • Energy=1/2[u(du/dt)+v(dv/dt)+w(dw/dt)] • Coriolis force and curvature terms are cancelled out • Cosine component of Coriolis force contributes to zonal vertical circulation • And r=a+z provides accurate curvature and displacement • Generalized vertical coordinates (Staniforth and Wood, 2003)

  26. Full Coriolis Effect • Sine component of it modifies the flow pattern at middle- and high-latitudes • Cosine component of it modifies the vertical flow patterns at tropic and extra-tropic areas. • Coriolis force is approached to 10-4 from f and 10 from u, so it is about 10-3, and w is 10-2, 10% effect in w.

  27. Not-shallow atmosphere For shallow assumption r = a (earth radius) For non-assumption r = a + z Not only affect gradients, curvature terms but also displacement by wind, since u = r cos d/dt and v = r d/dt For example, 50 m/s wind from100 hPa (20km) to 0.2 hPa (60km), errors in r=a are from 0.2 to above 1%, thus, errors in displacement after 10 days are from 20 km to 432 km.

  28. Final Note With the combinations of • Sigma-theta coordinates to reduce the errors in vertical advection • Deep atmosphere to reduce the errors in stratospheric horizontal advection • Full Coriolis effect to have better vertical circulation along tropical areas The improvement on dynamical weather and climate forecasts can be expected.

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