Over 20 towers measuring carbon, water, and heat flux.
The suffix .tar refers to the standard Tape Archive file format. In this context, it usually signifies a large, bundled dataset containing observations from: Cheesehead.tar
You can find the most detailed technical descriptions and the full data archives on the CHEESEHEAD Field Project page hosted by NCAR's Earth Observing Laboratory. CHEESEHEAD - Earth Observing Laboratory Over 20 towers measuring carbon, water, and heat flux