co 2 and o 2 concentration measurements britton stephens, ncar/atd peter bakwin, noaa/cmdl global...
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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