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TOPIC: Gust issue

Gust issue 1 week 5 days ago #406

  • Ruud
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Hello,
I noticed a remarkable phenomenon with gusts. In the attached example GFS shows gusty conditions in the warm sector before the front, and no gusts at all in the unstable air behind it. This is also the case in WRF. Icon and all other non GFS derived models show a much more realistic situation. Does anybody has an explanation for this? I find it difficult to believe that GFS is not aware of the physics behind meteorology...
Regards,
Ruud
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Gust issue 1 week 5 days ago #408

Hi Ruud,

You are comparing a hydrostatic model (GFS) with a non hydrostatic model (ICON). A hydrostatic model does not include the level of physic modules that the non-hydrostatic models have and this affects the area of resolving convection. Differences in boundary layer physics will also affect the resolving of gusts. This is not true in regards to WRF which can resolve gusts being a non-hydrostatic model (see the attached images).

In the attached examples you can see the GFS and also Arpege (Global) are very soft in gusts behind the front line. These are hydrostatic models
The images for openWRF, ICON, ICON_EU and Arpege_EU all show significantly more gust activity behind the front. These are non-hydrostatic models

It is not always just about resolution. There are different types of models that have different limitations.
By the way, GFS will be going non-hydrostatic when the new FV3 core becomes operational in the near future.

David

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Gust issue 1 week 5 days ago #409

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Hi David,

Thanks for your explanation and the learning moment. I was aware of the differences between non hydrostatic an hydrostatic models but did not realize that it could lead to misinterpretations of this extend. It raises the question why a model actually produces a parameter that it cannot adequately judge. Good that a solution is on its way...

Regards,
Ruud

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