RTM on coarser grid

[c_i_vantuyll@uu_nl]

Dear all,

I'd like to use a coarser grid for my coupled ccsm run.
Instead of the 0,5 deg grid we prefer to use a T42 resolution. This works fine, but I think I have to change the velocity and/or the frequency of this module, default is 3 hrs.
The reason why I think I have to change this is that it takes longer for a river to flow over a coarse grid cell. Especially during spinning up, so this issue will cause different equilibria depending on its velocity.

Does anyone have experience with this and knows some proper values? Many thanks in advance!

cheers car

 

[slevis]

Hi,

When you run the ccsm at some resolution other than 0.5x0.5 degrees, the RTM still runs at 0.5x0.5 degrees. It is hardwired to do so. Therefore, I do not think that you should change anything.

Sam Levis
CLM Scientific Liaison

 

[c_i_vantuyll@uu_nl]

Hi,
thanks for replying!
Of coarse, I know the 0.5 deg is better. However when you do not use the topography of present-day, you face a problem, as it is practically impossible to construct a proper rdirc file on a 0.5 deg grid.

Therefore, a known practice in paleo runs is to use the same gridsize as the land topography, T42. By doing this the dimensions and grid specifications have to be declared properly. And this works fine. The coupler, clm and pop data show proper mappings.

However, still the effective velocity of 0.35 m/s should be higher. And I was wondering if the frequency of /9timesteps is sufficient. So, I hope if someone have some experience in doing this. Thanks in advance!

car