GRUN
X axis: whole world in 720 0.50° steps, first point at 179.75° W, last point at 179.75° E
Y axis: regular grid with 360 0.50° steps, first point at 89.75° S, last point at 89.75° N

Monthly data available from Jan1902 to Dec2014 (1356 months)
Variable Runoff (Runoff) in mm/day
Full metadata.

Get grid points, average area or generate subset

Mask:	no mask mask37.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

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 runoff
Threshold:	no cut less than greater than mm/day 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

getfieldtype: please ask me to add "Runoff" to the lists in getfieldtype

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, GRUN runoff is available as a netcdf file (size 325.711 MB).