Regular partial sums are computed for each model (see here). Each model's forecast are verified against ONLYSFC (ADPSFC and SFCSHP) surface observations from the NAM PREPBUFR files and ADPUPA upper-air observations from the GDAS PREPBUFR files that fall in a 45 minute window of the valid time. Forecast are also verified against data from the International Arctic Buoy Programme (IABP) at their valid time. All data are regridded using bilinear interpolation, if needed, to the G003 (1x1 degree) grid for upper-air variables, to the G104 grid for surface variables, and to the grid G223 for the IABP verifcation.

Verification statistics are computed from the regular partial sums. The equations used to calculate the verification statistics can be found here. Statistical signifance is calculated using a student-t test.

The verification regions used are are: Global, N. Hemisphere: 20N-90N, S. Hemisphere: 20S-90S, Polar: 60S-90S and 60N-90N, and Arctic. Sea ice and sea ice free regions are determined from the sea ice fraction from the satellite or satellite analysis dataset. Information on the GHRSST NCEI AVHRR Analysis dataset can be found here. Information on the GHRSST OSPO Geo-Polar Analysis dataset can be found .