How to calculate freezing level using metpy

[krishnaap]

I have a model dataset in model levels (say 64), is there any function to calculate freezing level?

[dopplershift]

I'm not sure what exactly you mean by "model levels" (could be sigma, pressure, etc.). In general, what you want is to use something like interpolate_1d to interpolate one set of values (e.g. vertical coordinate) based on another set (e.g. temperature). We normally think of interpolating temperature to a fixed vertical level (e.g. 500 hPa), but what you want is to interpolate your vertical coordinate to a fixed temperature (0 degC). This example might be somewhat helpful.

[krishnaap]

I am using IMDAA reanalysis data and it has the Charney and Phillips (CP) vertical grid system ( DOI: https://doi.org/10.1175/1520-0469(1953)010<0071:NIOTQG>2.0.CO;2 ). I will check that example and update it here. Thank you so much @dopplershift again.

[krishnaap]

I tried with this small modification

freezinglev = [273.15] * units.K

height, press = (log_interpolate_1d(freezinglev, T, hgt, p, axis=1) 

but it is showing errors

IndexError: too many indices for array: array is 1-dimensional, but 3 were indexed

What is the issue here?

used variables are

T
Out[237]:
<xarray.DataArray (model_level_number_0: 64, latitude: 501, longitude: 751)>

hgt
Out[238]:
<xarray.DataArray 'level_height' (model_level_number: 63)>

p
Out[239]:
<xarray.DataArray 'air_pressure' (model_level_number_0: 64, latitude: 501, longitude: 751)>

[DanielAdriaansen]

In the documentation for log_interpolate_1d() here:
https://unidata.github.io/MetPy/latest/api/generated/metpy.interpolate.log_interpolate_1d.html

Variables hgt and p must have the same shape as T, but it appears that your hgt variable is not the same (63 vs 64). Try aligning the lengths of T, hgt, and p and see if that helps.