 

Field
GPCC #gauges
GPCC Full Data Monthly Product Version 2018, precipitation in mm/month, 1.0 degree
X axis: whole world in 360 1.00° steps, first point at 179.50° W, last point at 179.50° E Y axis: regular grid with 180 1.00° steps, first point at 89.50° N, last point at 89.50° S Monthly data available from Jan1891 to Dec2016 (1512 months) Variable numgauge (gpcc full data monthly product version 2018, number of stations per grid) in gauges per gridcell Full metadata. Construct a statistical forecast model from this field Compute anomalies
Compute zonal mean
If you really want to get it here, GPCC #gauges is available as a netcdf file (size 23.0011 MB). 
© KNMI
