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.

[vonjpthirvon]

Hello, this is old discussion but I recently had same task to find freezing levels from atmospheric sounding. I attach a code (freezing_levels.py) that worked for sounding data that I used. The code probably can be developed in many ways but my goal was make it the work in situations with more than one freezing level. This can happen if there is/are temperature inversion/s in the right way close to 0 degC temperature.
freezing_levels.py.txt