An Autonomous Inexpensive Robust CO
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An Autonomous Inexpensive Robust CO 2 Analyzer (AIRCOA). Britton Stephens, Andrew Watt, and Gordon Maclean National Center for Atmospheric Research, Boulder, Colorado, USA. Using high frequency data makes signals bigger, but the annual-mean signals are still very small:.

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An Autonomous Inexpensive Robust CO 2 Analyzer (AIRCOA)

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An autonomous inexpensive robust co 2 analyzer aircoa

An Autonomous Inexpensive Robust CO2 Analyzer (AIRCOA)

Britton Stephens, Andrew Watt, and Gordon Maclean

National Center for Atmospheric Research, Boulder, Colorado, USA


An autonomous inexpensive robust co 2 analyzer aircoa

Using high frequency data makes signals bigger, but the annual-mean signals are still very small:

To measure 0.2 GtCyr-1 source/sink to +/- 25% need to measure regional annual mean gradients to 0.1-0.2 ppm

Flux footprint, in ppm(GtCyr-1)-1, for a 106 km2 chaparral region in the U.S. Southwest (Gloor et al., 1999).


An autonomous inexpensive robust co 2 analyzer aircoa

NCAR CO2 and O2/N2 Calibration Facility


An autonomous inexpensive robust co 2 analyzer aircoa

CO2 signal averaged over 2.5 min. measurement cycle


An autonomous inexpensive robust co 2 analyzer aircoa

Calibration sequence


An autonomous inexpensive robust co 2 analyzer aircoa

Empirical pressure correction


An autonomous inexpensive robust co 2 analyzer aircoa

Empirical temperature correction

SPL 9/4-9/18

NWR 9/18


An autonomous inexpensive robust co 2 analyzer aircoa

Drying system monitoring

A change of 0.5% RH is approximately 300 ppm H2O, which would cause a dilution error of 0.1 ppm in CO2


An autonomous inexpensive robust co 2 analyzer aircoa

Nafion absorption effect

Flow pulled through Nafion went from 300 to 50 sccm at t = 30 sec


An autonomous inexpensive robust co 2 analyzer aircoa

Empirical flushing correction


An autonomous inexpensive robust co 2 analyzer aircoa

Automated (4- or 8-hourly) leak checks

A positive trend of 0.3 kPa/min would be a leak rate of 0.1 sccm which if 100 ppm different would cause a 0.1 ppm bias


An autonomous inexpensive robust co 2 analyzer aircoa

Regulator oven tests

Three cylinders were in the oven and one (green dots) was not


An autonomous inexpensive robust co 2 analyzer aircoa

Regulator flushing tests


An autonomous inexpensive robust co 2 analyzer aircoa

Laboratory intercomparisons

Laboratory offsets less than 0.05 ppm (1-sigma = 0.13 ppm)

Field surveillance tanks

2.5-month average field differences from assigned values 0.01 to 0.10 ppm (1-sigma = 0.10 to 0.13 ppm)


An autonomous inexpensive robust co 2 analyzer aircoa

Automated web-based output

http://www.eol.ucar.edu/~stephens/RACCOON


Power budget

Power Budget


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