Modified pyrgeometer calibration procedures were implemented beginning in February 2004.
These modified procedures introduced a calibration bias in the longwave data. The previous
procedures were re-implemented at all sites between December 2005 and February 2006 to
restore proper calibrations.
The data collected while the incorrect procedures were in place have been reprocessed to
remove the calibration bias. The reprocessed 60 second averaged data are based on 3
instantaneous 20 second data records rather than on 60 1 second instantaneous data records.
Still, these data are considered far superior to the originally processed data. The
reprocessed data were archived in August 2006.