Arkin and Janowiak GPI: IR -Based Monthly Rainfall for the GPCP 2.5 x 2.5 degree V1 (RAIN_ARKIN) at GES DISC
These data are transitioned to a state of permanent preservation. They are available upon request.
More advanced datasets have been developed since. 
One recommended replacement is the GPCP (doi: 10.5067/DBVUO4KQHXTK) product developed under the MEaSUREs project. 

The Arkin and Janowiak GPI (GOES Precipitation Index) …