September 4, 2008
-----------------

Version 1 of the Level 2, 3, and 4 files for the ARM Southern Great Plains
(SGP) main site (US-ARM) were posted.

January 9, 2009
---------------

Version 2 L2 files were posted.  The new files contain corrected CO2
concentrations at the 4.28 m height and have incoming global radiation
and longwave radiation values set to missing during late 2006.  The 4.28
m CO2 flux system was calibrated on May 25, 2005. After the calibration
was performed, the calibration coefficients used to measure CO2 were
not updated causing an offset. In addition, incoming global radiation
and incoming longwave radiation values during late 2006 were set to
missing because the downwelling longwave and shortwave irradiance 
channels were switched to diagnose a problem with the CNR1.

March 3, 2010
-------------

Version 3 for the L2 files were posted.  Version 3 contains the same
corrections noted for Version 2 and provide updates through the end
of 2009.  Air temperature in previous versions of the L2 files for the
US-ARM site were actual virtual temperatures from the sonic.  Version 3
now contains the actual measured air temperature from the tower.


October 6, 2011
---------------

Version 4 of the L2 files were posted.  Version 4 contains the corrections
noted for Versions 2 and 3, provides updates through 2010, and sets some
bad soil temperature values to missing.  

June 6, 2012
------------

Version 5 (V005) of the L2 files for the ARM Southern Great Plains main
site (US-ARM) were posted and provide data from 2002 through May 2012.


August 23, 2013
---------------

Version 6 (V006) of the L2 files for the ARM Southern Great Plains main
site (US-ARM) were posted and provide data from 2002 through January 2013.
Data before May 2012 are unchanged from V005.  Details on CDIAC's processing 
of the latest Level 1 files obtained from the DOE ARM Archive to produce 
these Level 2 files may be found at

ftp://cdiac.ornl.gov/pub/ameriflux/data/Level2/Sites_ByName/ARM_SGP_Main/with_gaps/report_ARM_SGP_Main.html