pm-fao56 method does not work for my Xarray.dataArray data about pyet

[mvremec]

Hi @Engel23,
Thank you for raising this issue.

Based on your description, it seems that the name of your DataArray's ("yourDataArray") time dimension is neither "time" or "index".

1. You can check whether this is the case with:
   yourDataArray.dims
   It should return something like "({'time': 3672, 'y': 17, 'x': 20})" or "({'time': 3672, 'latitude': 17, 'longitude': 20})". If it does not return 'time', you can fix this by changing the current name of the time dimension (for example, let's call it "timeindex"):
   newDataArray = yourDataArray.rename_dims({"timeindex":"time"})
   You should now be able to check the time dimension of the "newDataArray" with:
   newDataArray.time
   It should return an array with a dtype = 'datetime64[ns]'
   You should now be able to use "newDataArray" with PyEt.

I hope this answer solves your question. Please let me know!
Is the CMIP6 data publicly available? If so, I can create an example using a subset of the data.

Best, Matevz

---

Why did this probably happen?
In the FAO-56 method, the Day of the year (DOY) is needed to compute extraterrestrial radiation. In PyEt, DOY is obtained from the time dimension of the input Pandas.Series or xarray.DataArray. We have designed PyEt with an assumption that the xarray.DataArray time dimension is called "time" or "index". This is usually the case; however, there might be exceptions. That's why it's good to communicate on such issues. Thank you for that!

How to solve this in future versionsof PyEt?
Add a function that raises an error if the name of the time dimension in xarray.DataArray is not "time".
#43

[Engel23]

Hi @mvremec,
Thank you for your quick response and for your help, the dimension name was indeed where it went wrong since my dimension had a different name due to prior calculations. The pm-fao56 method seems to work now for my data! The CMIP6 data is publicly available here (https://esgf-node.llnl.gov/search/cmip6/), note that the variables needed for the pyet package (tasmax, tasmin, etc) are distributed into different netcdf files.

Again thank you for your help!
Best, Engel

[mvremec]

Hi @Engel23,
I am very glad to hear that.
I have added an example with CMIP6 data I downloaded from Copernicus (https://cds.climate.copernicus.eu/) and will probably extend it to the data from your link. Thank you for that!
Example 9: https://github.com/pyet-org/pyet/blob/dev/examples/09_CMIP6_data.ipynb

I wish you lots of fun and exciting work with PyEt!
Best,
Matevz