How to convert sigma level vertical velocity to pressure level?

[weatherforecasterwhai]

Thanks to @shoyer in #68 , I've got sigma level vertical velocity. So I try to use _model.model_coords.horizontal.to_nodal(vertical_velocity)_ as @shoyer said in https://github.com/google-research/neuralgcm/issues/8.

However it works with this error: size of label '1' for operand 1 (65) does not match previous terms (64). I've searched and can't fix it by myself. And as in #8, when running _model.model_coords.horizontal.to_nodal(advanced.state.temperature_variation)_ is ok. The full traceback is like this:

[shoyer]

I believe to_nodal and to_modal only operate on 2D arrays. If you want to transform a higher dimensional field, wrap the transformations in jax.vmap.

[weatherforecasterwhai]

Thanks to mention the dimension. 1.Then advanced.state.temperature_variation.shape is (32,128,65), and the vertical velocity shape is (32,128,64). So, maybe the to_nodal can operate on 3D array (32,128,65), but can't operate on (32,128,64), and the error lies between 65 and 64. More interesting thing is , the model.model_coords.nodal_shape is (32,128,64)! So, does it need one more grid to calculate from modal to_nodal? Running z=jnp.zeros((32,128,1)), and omega1=jnp.concatenate((omega,z),axis=2) to get (32,128,65) shape. It seems to work.

2.Running like _this xarray_utils.save_netcdf(xarray.DataArray(omega).todataset(name="omega"),"omega.nc") could save to a netcdf file, but it's not easy be read to Grads (it's a popular and easy ). While using neural_gcm_model.data_to_xarray(preditcions,times=times).to_netcdf('*.nc') is much better, its format is well defined.

Do you have a better way to 1.solve the dimension problem, 2. save to netcdf like neural_gcm_model.data_to_xarray? Thank you!

[shoyer]

1.Then advanced.state.temperature_variation.shape is (32,128,65), and the vertical velocity shape is (32,128,64). So, maybe the to_nodal can operate on 3D array (32,128,65), but can't operate on (32,128,64), and the error lies between 65 and 64.

Please double check, but I believe sigma level vertical velocity may already be defined in "nodal" space already (on the Gaussian grid), and hence does not need the to_nodal() transform.

2.Running like this xarray_utils.save_netcdf(xarray.DataArray(omega).to_dataset(name="omega"),"omega.nc") could save to a netcdf file, but it's not easy be read to Grads (it's a popular and easy ). While using neural_gcm_model.data_to_xarray(preditcions,times=times).to_netcdf('*.nc') is much better, its format is well defined.

You should use data_to_xarray(...).to_netcdf(). There is a lot of old stuff in xarray_utils that I would not recommend using, and we may remove to avoid confusion.

[weatherforecasterwhai]

@shoyer I don't understand the codes whether it outputs sigma level or pressure level. Please have a look at compute_vertical_velocity: def compute_vertical_velocity( state: State, coords: coordinate_systems.CoordinateSystem ) -> jax.Array: """Calculate vertical velocity at the center of each layer.""" sigma_dot_boundaries = compute_diagnostic_state(state, coords).sigma_dot_full assert sigma_dot_boundaries.ndim == 3 """This matches the default boundary conditions for vertical velocity from sigma_coordinates.centered_vertical_advection""" sigma_dot_padded = jnp.pad(sigma_dot_boundaries, [(1, 1), (0, 0), (0, 0)]) return 0.5 * (sigma_dot_padded[1:] + sigma_dot_padded[:-1])

[shoyer]

Vertical velocity (and everything inside the dynamical core) is output on sigma levels. If you want it on pressure levels, you can use the vertical interpolation routines from dinosaur.vertical_interpolation.

[weatherforecasterwhai]

Vertical velocity is really important to analyse weather, please make a easy api to output it in the same way as p_e or other variables. Thank you!

[shoyer]

Another option is to calculate vertical velcoity as a diagnosed variable from an output dataset on pressure levels with the WeatherBench2 code: https://weatherbench2.readthedocs.io/en/latest/_autosummary/weatherbench2.derived_variables.VerticalVelocity.html#weatherbench2.derived_variables.VerticalVelocity