I had previously written about a strange projection in the NOAA/CLIMAPS data, and am now following that up with a strange projection in the Climate Atlas of the US data. This data comes to the end user with no spatial reference or documentation on disk which describes the spatial reference. However, I found a helpful page on the climate atlas website which describes the reference: http://www.ncdc.noaa.gov/oa/about/cdrom/climatls2/faq.html#SPHEROID. This reference, however, is not a common one. A similar projection is available in ArcGIS though, and by modifying the reference latitude (i.e., latitude of origin), we can apply the new custom projection to these files by “define projection”. Here is a link to the custom projection file.