Hybrid sigma pressure levels to pressure levels

[LH-Chneg]

Dear all,
I am using NCL's interpolation function vinth2p,to make Hybrid sigma pressure levels to pressure levels,but the interpolation result is quite different from the result of CDO ml2pl,which may make me have a wrong understanding of hyam,hybm when I am using vinth2p function. formula = "p = a*p0 + b*ps" is hyam=a,hybm=b correct. I apologize for the intrusion and hope you can help me a little, thanks!

Best wishes,
Li

 

[strandwg]

Can you provide plots of the same data being interpolated by both CDO and NCL so the results can be compared.
Thanks!

 

[LH-Chneg]

Thank you for your response!
This is the data and graphs interpolated using NCL and cdo, and you can see that there is a large difference between the two. At the risk of asking ah, can this formulas = "p = a*p0 + b*ps" of atmosphere_hybrid_sigma_coordinates be interpolated to barometric coordinates by NCL's vinth2p function, and also can CDO's ml2pl be interpolated? Hope to get your reply!

 

[strandwg]

Thank you for your response!
This is the data and graphs interpolated using NCL and cdo, and you can see that there is a large difference between the two. At the risk of asking ah, can this formulas = "p = a*p0 + b*ps" of atmosphere_hybrid_sigma_coordinates be interpolated to barometric coordinates by NCL's vinth2p function, and also can CDO's ml2pl be interpolated? Hope to get your reply!

I'm not very familiar with CDO but it probably has a mailing list for questions.

NCL has a mailing list for questions and issues; please see

https://mailman.ucar.edu/mailman/listinfo/ncl-talk

 

[zarzycki]

Not sure this is CESM data, but I strongly suggest checking the hybrid coordinate formulation.

The NCL function you use assumes the CESM formulation, which has an hya coefficient multiplied by p0: 3.5 Model Vertical Coordinate

Other centers apply different formulations. Ex: ECMWF:

ERA5: compute pressure and geopotential on model levels, geopotential height and geometric height - Copernicus Knowledge Base - ECMWF Confluence Wiki

confluence.ecmwf.int

I believe the primary difference stems from scaling the term hya term attached to the constant p0 (CESM does, ECMWF does not), although there may be others.

The 1.png and DATA.png from your first and second posts imply one of the levels is calculated using a scaled a term and the other is calculated using an absolute a term.

 

[LH-Chneg]

Thank you for your reply! I looked up some information about Hybrid sigma pressure levels to pressure levels, the conclusion of using CDO's method is correct, while NCL's vinth2p is not applicable with this coordinate and other methods have to be used.