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| 2 | This test case is described in the paper "A proposal for the |
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| 3 | intercomparison of the dynamical cores of atmospheric general |
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| 4 | circulation models" by Held and Suarez (HS94, Bulletin of the American |
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| 5 | Meteorological Society; 1994, Vol 75, 1825-1830), and you should read |
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| 6 | this paper for a detailed description of the test configuration and |
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| 7 | expected test results. |
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| 8 | |
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| 9 | This test of the global solver is dry (no moist effects or moisture), |
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| 10 | there is no terrain, and the flow is driven by an imposed forcing and |
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| 11 | dissipation. The forcing (a prescribed temperature distribution towards |
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| 12 | which the atmosphere is relaxed) and dissipation (a simple drag term in |
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| 13 | the lower atmosphere) produces midlatitude jets, breaking midlatitude |
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| 14 | baroclinic waves, etc. |
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| 15 | |
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| 16 | The default ARW namelist specifies a one-thousand day integration for |
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| 17 | this test - that is approximately the length of the simulations |
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| 18 | presented in HS94, where statistics of the flow are calculated using |
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| 19 | time averaged fields from the last few hundred days of the simulations. |
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| 20 | The midlatitude jets and baroclinic instabilities appear early (within |
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| 21 | the first 100 days) so long integrations are not required to observe |
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| 22 | the main features of the flow. The default ARW configuration for this |
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| 23 | test case is very coarse - much coarser horizontal resolution than that |
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| 24 | presented in HS94, so care should be taken in comparing any results from |
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| 25 | the default configuration to the HS94 results (the coarse grid allows |
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| 26 | one to run the long simulation on a single processor of a present-day |
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| 27 | PC). The HS94 results are presented in the form of vertical cross |
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| 28 | sections of zonal means, which are not standard analysis plots for the |
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| 29 | ARW plotting packages. The results are also sensitive to the horizontal |
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| 30 | dissipation (numerical filters) used in these simulations. |
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| 31 | |
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| 32 | There is no exact solution for this test, so the results can only be |
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| 33 | compared with that from others models in a qualitative manner. |
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