Both numerical modeling and laboratory experiments document the possibility of a raindrop size distribution
(DSD) to evolve to an equilibrium stage (EDSD), where all the principal processes occur at steady rates.
The aim of this work is to observe the temporal behavior of the DSD and to directly investigate the conditions
favorable to the onset of the EDSD in natural rain. We exploited a large disdrometer dataset collected in the
framework of the Ground Validation activities related to the NASA Global Precipitation Measurement mission.
More than 200,000 one-minute data of two-dimensional video disdrometer (2DVD) are collected over USA to
represent a wide range of precipitation types. The original data are averaged over 2 min and an automatic
algorithm is used on a selected subset to identify samples with EDSD. Results show that the EDSD occurs mainly
in convective events and lasts for very short time intervals (2 to 4 min). It is more frequent for rain rate between
20 and 40 mm h−1 and it mostly occurs during sharp increase of precipitation rates
