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P. Rípodas 1 , A. Gassmann 2 , G. Zängl 1 , D. Reinert 1 and H. Wan 2

ICON Non-Hydrostatic Dynamical Core Idealized test case results with triangles and hexagons/pentagons as primal grids. P. Rípodas 1 , A. Gassmann 2 , G. Zängl 1 , D. Reinert 1 and H. Wan 2 1 Deutscher Wetterdienst, Offenbach (Main), Germany

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P. Rípodas 1 , A. Gassmann 2 , G. Zängl 1 , D. Reinert 1 and H. Wan 2

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  1. ICON Non-Hydrostatic Dynamical Core Idealized test case resultswith triangles and hexagons/pentagons as primal grids P. Rípodas1, A. Gassmann2, G. Zängl1, D. Reinert1 and H. Wan2 1Deutscher Wetterdienst, Offenbach (Main), Germany 2Max Planck Institute for Meteorology, Hamburg, Germany

  2. ICON Non-Hydrostatic dynamical core (ICONAM) : We have two versions of ICONAM, with triangles and hexagons/pentagons as primal grids.

  3. COMPARISON OF BOTH VERSIONS IDEALIZED TEST CASES: Jablonowski-Williamson steady state (JWs) Jablonowski-Williamson baroclinic wave (JWw) Mountain induced Rossby wave (MRW) GRID LEVELS: R2B04 – R2B07 (up to 20 km) Time steps: 320s – 40s MODEL SETTINGS: Spring dynamics grid optimization, 4th-order diffusion (velocity field), 35 vertical levels (23.5 km) RESULTS FOR THE SURFACE PRESSURE (PS)

  4. Jablonowski-Williamson steady state Geostrophically and hydrostatically balanced flow. Constant PS=1000 hPa It is a steady state but dynamically unstable. Due to the irregular structure of the triangular grid, the zonal symmetry is lost after some days and low and high pressure systems are developing. Triangles, 17km, 40s PS at day 15 999.23 – 1000.7 hPa

  5. Jablonowski-Williamson steady state The analytical solution is known-> errors can be calculated. The model is considered to be unable to maintain the balanced flow when the PS l2 error increases beyond a certain threshold level (0.5 hPa) (Lauritzen et al., 2009) A convergence is observed in the number of days that PS l2 is below 0.5 hPa. Very similar result for triangles and hex/pent.

  6. Jablonowski-Williamson baroclinic wave The initial conditions are the same as in JWs but with a perturbation in the zonal wind field → a baroclinic wave is triggered and reach its mature stage at day 9 We consider ECHAM (hydrostatic spectral general circulation model developed at MPI-M) as reference. ECHAM T799 PS day 9

  7. Jablonowski-Williamson baroclinic wave 139 – 240 km PS at day 9 at different resolutions A phase delay is observed for coarse resolutions for triangles and hexagons 69 – 120 km 35 – 60 km 17 – 30 km

  8. Jablonowski-Williamson baroclinic wave Comparison to ECHAM5 T799: ICONAM-ECHAM PS differences at day 9 triangles hexagons R2B06 35 km 60 km R2B07 17 km 30 km A convergence of ICONAM is observed. The triangle and hexagon versions have very similar results.

  9. Jablonowski-Williamson baroclinic wave ICONAM hexagons - triangles differences (PS, day 9) R2B05 69 – 120 km R2B07 17 – 30 km min -2.2 hPa max 1.8 hPa min -7.3 hPa max 5.9 hPa Differences between triangles and hex/pent versions decrease with increasing resolution. Differences between triangles and hex/pent versions are smaller than differences between ICONAM and ECHAM. R2B06 35 – 60 km min -3.4 hPa max 2.2 hPa

  10. Mountain induced Rossby Wave Smooth isothermal initial conditions that are a balanced analytic solution to the primitive equations. An idealized mountain triggers the evolution of a Rossby wave train. ECHAM5 T799 PS at day 15 PS at day 0

  11. Mountain induced Rossby Wave Comparison to ECHAM5 T799 : ICONAM – ECHAM PS differences at day 15 →no convergence is observed R2B06 triangles hex/pent 35 km 60 km R2B07 triangles hex/pent 17 km 30 km

  12. Mountain induced Rossby Wave • Is the MRW ECHAM solution a good reference? • The hydrostatic version of ICON (ICOHAM) shows a convergence to the ECHAM solution • ICOHAM and ECHAM solutions use the same vertical level distribution, 31 vertical hybrid levels up to 0hPa but ICONAM uses 35 vertical height based hybrid levels up to 23.5 Km • ICONAM with 40 levels (up to 35 Km) is closer to the ECHAM solution than ICONAM with 35 level (up to 23.5 Km) • → ECHAM MRW solution can not be used as a reference for ICONAM because the solution depends sensitively on the depth of the simulation domain and on the reflection characteristics of the upper boundary

  13. Mountain induced Rossby Wave ICONAM hexagons - triangles differences (PS, day15) R2B04 (139 – 240 km) R2B06 (35 – 60 km) R2B05 (69 – 120 km) The largest differences are at the mountain position. Differences between the two model versions decrease with resolution.

  14. Mountain induced Rossby Wave hex/pent R2B07 30 km hex-tri differences R2B07 triangles R2B07 17 km ECHAM T799 At high resolution short wave-length differences between triangles and hex/pent versions and ECHAM appear.

  15. Conclusions • Two versions of ICONAM (triangles and hex/pent) have been tested and compared • using idealized test cases for resolutions up to 20 Km • For the JW steady state test case both versions of the model have very similar • results, a convergence is observed in the number of days for which the model maintains the initial balance of the flow. • For the JW baroclinic wave test case, both versions of the model have very similar • results. Differences between both versions decrease with increasing resolution. A convergence to an ECHAM solution used as reference is observed. • For the MRW test case the ECHAM solution can not be used as reference. • Differences between both versions decrease with increasing resolution. • It is planned to implement the Held-Suarez test for the Non-Hydrostatic core.

  16. THANK YOU FOR YOUR ATTENTION

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