Fractional nest domain

[kishoreragi]

Hi,

I want to make a nest domain with a fractional ratio. For example, 2 km parent resolution to 1.5 km nest resolution. Is there any workaround to achieve this?

Thank you.

Kishore

 

[kwerner]

Kishore,
Unfortunately the grid ratio can only be an integer. If you want your innermost domain to be 1.5 km, I would recommend having a more coarse parent domain. So, for e.g., you could set parent_grid_ratio = 1, 3 and dx/dy = 4500, 1500.

 

[janac4]

Kishore,
Unfortunately the grid ratio can only be an integer. If you want your innermost domain to be 1.5 km, I would recommend having a more coarse parent domain. So, for e.g., you could set parent_grid_ratio = 1, 3 and dx/dy = 4500, 1500.

Hello,
I am using GFS (0.25º resolution) as initial data for my WRF model. It is a one-way nesting model with ratio 1:5 so my inner domain has 5 km horizontal resolution. I was wondering if it is possible to add a domain in between them to compare results in the 5 km resolution one. However I'm not sure I can achieve this 25 km to 5 km downscaling with an additional domain with ratios the model can handle.
Do you think it is possible?
Thank you.

 

[kishoreragi]

Unfortunately, it is not possible. However, I don't understand why it is not possible when the inner domain input is always interpolated irrespective of being an integer and a fraction. In future versions, it would be fantastic if users had the ability to set fractional grid ratios.

 

[janac4]

Unfortunately, it is not possible. However, I don't understand why it is not possible when the inner domain input is always interpolated irrespective of being an integer and a fraction. In future versions, it would be fantastic if users had the ability to set fractional grid ratios.

Thank you for your response,
However, I believe I may not have expressed myself clearly. I was initially seeking an integer ratio for transitioning from the native 25 km resolution (GFS) to a 15 km parent domain and further down to a 5 km inner domain. In reality, WRF only requires an integer ratio between the parent and inner domains (15 / 5 = 3) and does not consider the ratio between the input GFS files and the coarser domain (25 / 15). In my namelist.wps I should set:
parent_grid_ratio = 1, 3,
dx = 15000,
dy = 15000,

I could compare this results with my previous simulation, which involved a single domain transition from GFS to WRF 5 km, to better understand the impact of adding the 15 km domain. Does this approach seem correct?