GPCC Full Data Product version 7, precipitation in mm/month, 2.5 degree combined with the GPCC monitoring product combined with the GPCC monitoring product combined with the GPCC monitoring product combined with the GPCC monitoring product combined with the GPCC monitoring product
X axis: whole world in 144 2.50° steps, first point at 178.75° W, last point at 178.75° E
Y axis: regular grid with 72 -2.50° steps, first point at 88.75° N, last point at 88.75° S

Monthly data available from Jan1901 to Dec2017 (1404 months)
Variable prcp (precipitation) in mm/month
Full metadata.

Get grid points, average area or generate subset

Mask:	no mask mask10.txt   add a mask to the list
Latitude:	°N - °N
Longitude:	°E - °E
Boundaries:	halfway grid points interpolated
Make:	average max min set of grid points subset of the field
Demand at least:	% valid points in this region
Units:	convert to mm/day leave in mm/month

Create a field with lower time resolution

New time scale:	annual (Jul-Jun) annual (Jan-Dec) biannual seasonal
New variable:	mean sd sum sum above sum below number min time of min max time of max first time last time of precipitation
Threshold:	no cut less than greater than mm/month percentile normal 1971-2000
Minimum:	% valid data
First apply:	-month running mean
Missing data:	ignore, climatology, trend, persistence.

Create a field with lower spatial resolution

Average over blocks of longitude and latitude grid cells

Construct a statistical forecast model from this field

Please consider downloading this field from the authoritative site.
If you really want to get it here, GPCC+monitoring precipitation is available as a netcdf file (size 23.3884 MB).