CO2 Profiles from the Howland Integrated Forest Study Site, Howland, Maine

E. Davidson and E. Belk

Note: the datafiles have been encrypted using hfcrypt, an encryption program
available at ftp://io.harvard.edu/pub/software for a variety of platforms.
The key is necessary for decryption; to obtain it, contact Elizabeth Belk at
ebelk@whrc.org.

Since 1991, profiles of CO2 have been measured from a walk-up tower in the 
Howland Integrated Forest Study Site, Howland, Maine.  The CO2 profiling system
continuously draws in air from four levels of the tower, located 8.5m, 13.5m, 
19.5m, and 26.5m above the ground.  All four levels are completed every twelve 
minutes.  Air from the sample line is delivered to and analyzed by a LI-COR 
6251 infrared gas analyzer.  

The associated files list data corrected for drift of the IRGA (which is 
quantified by the twice daily checks of three reference gases).  The files 
are named with the Julian dates they cover.  The columns list the year, Julian 
date, time (hour-minute), corrected CO2 (in ppm) for level 1, level 2, level 
3, and level 4, respectively.