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Different results between adaptive time step and constant dt #1212
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@smileMchen Notice that the values that you are showing have a distinctive wave pattern (+ - + - + - +, etc). That likely points to not really having a bias, but more of a temporal / spatial offset between the solutions. What I have seen people do is to run two identical simulations, one with and the other without perturbed ICs. Then look at the resulting differences. You can re-run each of these existing two cases with perturbed ICs with namelist options:
Then you will have 4 total cases (two from unperturbed ICs, and two from perturbed ICs). It would be interesting to see those various six pairs of difference fields: C(4,2). |
@davegill |
@smileMchen |
For the same case running with constant time step and adaptive time step, the results can be quite different. The longer the integration period is, the larger the differences would be.
This is a problem that exists at least since WRFV3.8.
A test case using WRFV4.2 shows that after 48-hour integration, T2 difference could be within (-4, 4) and rain can be within the range f (-9mm, 9mm). Below is an example that shows the difference in RAINNC after 48 hours of integration.
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