Vertical levels within the boundary layer for HRRR?

[nicholasbalasus]

Hello,

I am looking at the native model level files from HRRR:

wget https://noaa-hrrr-bdp-pds.s3.amazonaws.com/hrrr.20190101/conus/hrrr.t00z.wrfnatf00.grib2

In these files, I'd like to know which of the levels are beneath the boundary layer. I can't seem to figure out a way to compare the units of the boundary layer height (meters, perhaps above the surface) to any information I am given about the levels (pressure, geopotential height) which are "hybrid sigma-terrain-following".

I will include below examples of how to extract these variables. I was wondering if there are any tools in MetPy that would allow me to determine which of the vertical levels are within the boundary layer. Thank you for any help that you can provide!

import xarray as xr

with xr.open_dataset("hrrr.t00z.wrfnatf00.grib2", engine="cfgrib", backend_kwargs={'filter_by_keys':{'typeOfLevel': 'hybrid'}}) as nat:
    vertical_levels_geopotential_height = nat["gh"]
    vertical_levels_pressure = nat["pres"]

with xr.open_dataset("hrrr.t00z.wrfnatf00.grib2", engine="cfgrib", backend_kwargs={'filter_by_keys':{'typeOfLevel': 'surface', 'stepType': 'instant'}}) as sfc:
    surface_height = sfc["orog"]
    boundary_layer_height = sfc["blh"]

for var in (vertical_levels_geopotential_height, vertical_levels_pressure, surface_height, boundary_layer_height):
    print(var.long_name)
    print(var.units)
    print(var.standard_name)
    print()

> Geopotential height
> gpm
> geopotential_height
> 
> Pressure
> Pa
> unknown
> 
> Orography
> m
> geopotential_height
> 
> Boundary layer height
> m
> unknown

[dopplershift]

MetPy has sigma_to_pressure which should help in converting to pressure coords, but otherwise I'm not sure what the right way is to accomplish what you want.

[nicholasbalasus]

Thank you, @dopplershift! I think I'll need to wait for some guidance from those that distribute the HRRR on this one. I appreciate your help!