This project deals with the study of autoconversion process, that is the process of transition between cloud droplets and precipitation: many connected open problems are currently object of study from the scientific community, like for example the need to be able to retrieve LWC for situations in which drizzle and cloud droplets are both present, the necessity to understand under which conditions clouds begin to precipitate and which are the corresponding threshold values for the onset of precipitation for LWP and other important variables. The aim of this PHD is therefore to try to study the process of formation of precipitation and derive such thresholds, verifying if they are consistent with models. Initially, the fellow will analyse LWP values with respect to the onset of precipitation as identified from different sources, then the analysis of temporal developments of Doppler spectra and its higher Doppler moments will be performed in order to identify thresholds values indicative of certain processes. Then, the results obtained will be implemented in the algorithm in order to improve the retrievals.