Single-cell NDIR-based measurements of atmospheric C02 mole fractions measured at Ameriflux towers, 2006 - 2016

Data collected via relatively low-cost, high-precision CO2 mixing ratio measurement systems, developed in collaboration with NCAR-ATD, are reported here. These data were collected to support inverse analyses of the terrestrial carbon balance at regional to continental scales. The systems use LICOR-820 non-dispersive infrared analyzers rather than the more expensive, but lower noise LICOR-6262 or LICOR-7000, since fast time response is not required for this application and the noise of the LICOR-820 can be reduced sufficiently by averaging over two minutes. Two nafion driers are used, ensuring that the difference in water vapor concentration between the dried sample and the moistened calibration gases is less than 300 ppm (corresponding to an error in the [CO2] measurement of 0.1 ppm). Flow control, such that the flow rate changes by less than 4 cc/min between the sample air and calibration gases, is achieved using a mini-regulator. Leak tests are automated and the systems are temperature controlled. For more information, see Stephens et al. (2011). The locations of the measurements are Austin Cary, FL Canaan Valley, WV Chestnut Ridge, TN Missouri Ozarks, MO Fort Peck, MT Tower heights ranged from 3 m AGL to 61 m AGL (See tower site information in the Data Access/Data Download section)