Change default value of atmosphere core config_number_of_sub_steps from 2 to 4 - #1496
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Change default value of atmosphere core config_number_of_sub_steps from 2 to 4#1496mgduda wants to merge 1 commit into
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…om 2 to 4 This commit changes the default value of the atmosphere core namelist option config_number_of_sub_steps from 2 to 4 in the Registry.xml file. This change addresses an issue in convection-permitting simulations where noise can sometimes appear in the jet streams using the previous default value (config_number_of_sub_steps = 2). The noise, when present, also produces unphysical features in horizontal kinetic energy spectra at high wavenumbers.
mgduda
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July 28, 2026 23:27
jeguerra-2025
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This is a fine default setting if it promotes an overall more stable time integration of the model. I'm confident it does. But, if it results in a ~10% runtime penalty, can we look for a way of compensating for that added cost? Does the added stability allow us to use a slightly longer time step for example?
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This PR changes the default value of the atmosphere core namelist option
config_number_of_sub_stepsfrom 2 to 4 in theRegistry.xmlfile. This change addresses an issue in convection-permitting simulations where noise can sometimes appear in the jet streams using the previous default value (config_number_of_sub_steps = 2). The noise, when present, also produces unphysical features in horizontal kinetic energy spectra at high wavenumbers.Note: Increasing the number of sub-steps from 2 to 4 can be expected to increase the computational cost of the dynamics by ~10%, and the computational cost of a full-physics simulation by ~5%.