Altitude of native HRRR levels?

[nicholasbalasus]

Hello - I am interested in using the average winds within the boundary layer with HRRR outputs.

I am using the native level files.

grib_file = "hrrr.t00z.wrfnatf00.grib2"

I seem to be able to get the boundary layer height (in meters) like this:

with xr.open_dataset(grib_file, engine="cfgrib",\
backend_kwargs={'filter_by_keys': {'stepType': 'instant',\
'typeOfLevel':'surface'}}) as ds:
    
    blh = ds["blh"].values

I can get the u and v winds on the pressure grid like this:

with xr.open_dataset(grib_file, engine="cfgrib",\
backend_kwargs={'filter_by_keys': {'typeOfLevel':'hybrid'}})\
as ds:
    
    u = ds["u"].values
    v = ds["v"].values

I'd like to average all of the u and v winds if their level is below the boundary layer height. I can't seem to find a variable for the height of the hybrid layers that I could compare to the boundary layer height. I suspect I am just missing the variable somewhere (or maybe I can just convert the geopotential height variable?)

Tagging @blaylockbk as they seem to be an expert on this!

Thanks,
Nick

[EricJames-NOAA]

@nicholasbalasus thanks for the question and sorry for the very late reply. I think you should be able to subtract the geopotential height on the native model levels from the geopotential height at the surface to get a geopotential height above ground level. Then you could convert this to a geometric height for comparison with the PBL height.