CO 2 and O 2 Concentration Measurements Britton Stephens, NCAR/ATD Peter Bakwin, NOAA/CMDL Global carbon cycle Regional scale CO 2 measurements Potential biases in NDIR CO 2 measurements Results from the WLEF O 2 measurement program Hands on: Calculating ppm from volts using different techniques

The Global Carbon Cycle Humans Atmosphere /yr Ocean 38,000 Land 2000 ~90 ~120 8 GtC/yr ~90 “Sinks” for anthropogenic CO 2 are very small relative to natural fluxes We need to understand current sinks to predict future CO 2 and climate (figure courtesy of Scott Denning)

Expected from fossil fuel emissions Observations TransCom1 FF Gradients What do existing flask measurements tell us?

Annual-mean CO 2 Exchange (GtCyr -1 )

Regional scale is critical for linking to underlying processes (NRCS/USDA, 1997) (SeaWIFS, 2002) CHLOROPHYLL TEMPERATURE (C) (IPCC, 2001)

(LSCOP, 2002)

TURC/NDVI Biosphere, Takahashi Ocean, EDGAR Fossil Fuel (Ute Karstens and Martin Heimann, 2001)

Flux footprint, in ppm(GtCyr -1 ) -1, for a 10 6 km 2 chaparral region in the U.S. Southwest (Gloor et al., 1999). Using high frequency data makes signals bigger, but the annual-mean signals are still very small:

Assessing horizontal CO 2 transport at eddy-flux sites similarly requires networks of independent, accurate CO 2 measurements

Takehome Points Strong needs exist for measuring regional and local scale continental CO 2 gradients Measuring CO 2 gradients with independent instruments requires careful attention to potential biases New models are also needed to extract information from continental CO 2 measurements

CO 2 and O 2 Concentration Measurements Britton Stephens, NCAR/ATD Peter Bakwin, NOAA/CMDL Global carbon cycle Regional scale CO 2 measurements Potential biases in NDIR CO 2 measurements Results from the WLEF O 2 measurement program Hands on: Calculating ppm from volts using different techniques

Flux footprint, in ppm(GtCyr -1 ) -1, for a 10 6 km 2 chaparral region in the U.S. Southwest (Gloor et al., 1999). Using high frequency data makes signals bigger, but the annual-mean signals are still very small: To measure 0.2 GtCyr-1 source or sink to +/- 25% need to measure annual mean gradients to around +/- 0.2 ppm

Intra- and Inter-laboratory agreement still not better than 0.2 ppm

Atmospheric Observing Systems Boulder, Colorado NOAA SBIR Robust, Precise, CO 2 Analyzer for Unattended Field Use Under Development 1 part in 3000 in 1 minute or less 30 cc/min or less gas usage Unattended field deployment for 6 months or more $5,000 or less when manufactured in quantity

Prototype Inexpensive/Autonomous CO 2 System Research items: Stability of CO 2 in aluminum LPG cylinders Correction for zero drift between calibrations Goals: 1-2 year service schedule Total installation ~ $ ppm accuracy RMT, Ltd., Russia

Towers over 650 feet AGL in U.S. and proximity