CO2 and O2 Concentration Measurements

Britton Stephens, NCAR/ATD

Peter Bakwin, NOAA/CMDL

• Global carbon cycle

• Regional scale CO2 measurements

• Potential biases in NDIR CO2 measurements

• Results from the WLEF O2 measurement program

• Hands on: Calculating ppm from volts using different techniques

The Global Carbon Cycle

Humans

Atmosphere

760 + 3/yr

Ocean

38,000

Land

2000

~90

~120

~120

8 GtC/yr

~90

“Sinks” for anthropogenic CO2 are very small relative to natural fluxes

We need to understand

current sinks to predict future

CO2 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 CO2 Exchange (GtCyr-1)

Regional scale is critical for linking to underlying processes

(NRCS/USDA, 1997)

(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 106 km2 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 CO2 transport at eddy-flux sites similarly requires networks of independent, accurate CO2 measurements

Takehome Points

• Strong needs exist for measuring regional and local scale continental CO2 gradients

• Measuring CO2 gradients with independent instruments requires careful attention to potential biases

• New models are also needed to extract information from continental CO2 measurements

CO2 and O2 Concentration Measurements

Britton Stephens, NCAR/ATD

Peter Bakwin, NOAA/CMDL

• Global carbon cycle

• Regional scale CO2 measurements

• Potential biases in NDIR CO2 measurements

• Results from the WLEF O2 measurement program

• Hands on: Calculating ppm from volts using different techniques

Flux footprint, in ppm(GtCyr-1)-1, for a 106 km2 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, CO2 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 CO2 System

Research items:

• Stability of CO2 in aluminum LPG cylinders

• Correction for zero drift between calibrations

Goals:

• 1-2 year service schedule

• Total installation ~ $2000

• 0.5 ppm accuracy

RMT, Ltd., Russia

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