This data set has been superseded by others. The data set is fine, but it is not being updated.
Most of my analyses with this data set have been with time series of area average precipitation anomalies for large regions. This sort of averaging is effective at picking out climate variability signals related to ENSO. An example of this sort of analysis is the time series equatorial Pacific island precipitation, plotted below with equatorial Pacific SST anomalies for the period 1890-1992.
Documentation of the data
Eischeid, J. K., C. B. Baker, T. R. Karl, and H. F. Diaz, 1995: The quality control of long-term climatological data using objective data analysis. J. Appl. Meteor., 34, 2787-2795.