ICOADS 2-degree Enhanced
X axis: whole world in 180 2.00° steps, first point at 1.00° E, last point at 359.00° E
Y axis: regular grid with 90 -2.00° steps, first point at 89.00° N, last point at 89.00° S

Monthly data available from Jan1800 to Dec2018 (2628 months)
Variable slp (Sea Level Pressure Monthly Mean at Surface) in millibars
Full metadata.

Get grid points, average area or generate subset

Mask:	no mask mask3.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 mb leave in millibars

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 SLP
Threshold:	no cut less than greater than millibars 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

Compute geostrophic wind components from this field

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, ICOADS v2.5 SLP is available as a netcdf file (size 81.226 MB).