As of January 19, 2021, FTP access to the GPM research / production data server "arthurhou" is no longer available, and you must use either FTPS or HTTPS to access GPM research data. Click here to learn more.

What causes precipitation to fall?

Precipitation forms when cloud droplets or ice particles in clouds grow and combine to become so large that the updrafts (e.g. upward moving air) in the clouds can no longer support them, and they fall to the ground.