For the NH there were 54 sites and for the SH 32. Site 9 (WMO ID 21504) is always missing, even with hadcrut2v. The site is located on an island in the Laptev Sea. There isn't a surface site anywhere near it. I could move the location and pick up the nearest CRU box, but it will be over 5 deg of lat and 10 deg of long away. It's somewhat unusual for sonde sites not to have a surface site near them. I guess it just doesn't report its surface data.
Arctic Approaches Ten Year Summer Sea Ice Maximum
4 minutes ago