Presence of rain or non-rainy clouds

I have radiosoundings that I want to flag as clear sky/cloud/rain. In absence of co-site meteorological instruments, I want to use ERA5 data to detect the presence of either rain or non-rainy clouds. ¿What parameters would be the most suitable? My ideas:

  • Rainy conditions: Using the parameter "Precipitation type" (+/- 1 hour radiosonde launching time)
  • Non-rainy clouds: If rain is not detected by "Precipiation type" , would use the parameter "Cloud base height" combined with "Precipitation type" (+/- 1 hour radiosonde launching time)

I know spatial resolution can be an issue, because in some cases the distance between the site and closest grid point is about 13 km. 

Some comments or ideas?