"Ring%202":

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"Ring 2"  High-precision, high-accuracy CO2
mixing ratio measurements in support of the NACP
Mid Continent Intensive
Scott Richardson, Natasha Miles, Kenneth Davis
(PSU), Eric Crosson (Picarro, Inc.), Scott
Denning, Marek Uliasz, Dusanke Zupanski (CSU)
ring2.psu.edu
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The Ring of Fire
The Ring of Towers

• Love is a burning thingand it makes a firery
  ringbound by wild desireI fell in to a ring of
  fire...I fell in to a burning ring of fireI
  went down,down,downand the flames went
  higher.And it burns,burns,burnsthe ring of
  firethe ring of fire.

• CO2 is a burning thingand it makes a warmer
  ringbound by wild desireI fell in to a ring of
  CO2...I fell in to a burning ring of CO2I went
  down,down,downand the CO2 went higher.And it
  burns,burns,burnsthe ring of CO2the ring of CO2.

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ChEAS Regional Flux Experiment Domain
LI-820 sampling from 75m above ground on a
communications tower.
40m Sylvania flux tower with high-quality
standard gases.
447m WLEF tower. LI-820, CMDL in situ and
flask measurements.
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Mid-Continent Intensive

• Overall goal Seek convergence between top-down
  and bottom-up ecological estimates of the
  regional flux
• Focus on upper Midwest of the U.S.

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The role of Ring 2 in the Mid-Continent Intensive

• Add regional network of 5 communications-tower
  based atmospheric CO2 obs in the midcontinent
  intensive region
• April 2007 through October 2008
• In addition to the planned long-term atmospheric
  CO2 observing network
• Tall towers
• Aircraft profiles
• Well-calibrated CO2 measurements on AmeriFlux
  towers
• The communications towers will oversample the
  atmosphere in the study region for more than a
  full year
• A coupled atmosphere/terrestrial carbon model and
  a Lagrangian particle dispersion model will be
  used to conduct an atmospheric inversion and
  convert these mixing ratio measurements into
  highly data-constrained regional carbon balance
  estimates.
• This work builds upon the Ring of Towers which
  deployed similar methodology in a forested region
  of northern Wisconsin

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Ring 2 sites

•   
• Kewanee, IL
• Centerville, IA
• Mead, NE
• Round Lake, MN
• Highland, WI

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Round Lake, MN 100 ft agl 360 ft agl
Kewanee, IL 100 ft agl 460 ft agl
Centerville, IA 100 ft agl 360 ft agl
Mead, NE 100 ft agl 400 ft agl
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Cavity Ring-Down Spectroscopy
gt A laser-based optical technique gt
Sensitivity Extremely long effective
path length Insensitive to optical power
fluctuations gt Chemical Specificity
Able to distinguish individual absorption
features gt Linearity Beer-Lambert Law
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Cavity Ring-Down Spectroscopy

• Picarro, Inc. has developed an ultra-sensitive
  trace gas (CO2, methane, CO) monitoring system.
  Advantages include

• High precision and accuracy
• long-term stability days to weeks
• 1.5-sec sample precision and accuracy of 0.2
  ppm and in tests
• Measurement rate in seconds rather than minutes
• No drying is required water vapor is measured
  and correction to CO2 is applied
• Stable and robust long-term measurement

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Predeployment tests

• Prior to deployment, the five cavity ring-down
  systems were tested together with two PSU
  Ameriflux systems. 
• For details on the low-cost systems, see
  www.amerifluxco2.psu.edu.
• Overall agreement 0.2 ppm

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Cavity Ring-Down Spectroscopy

• Long-term stability is unknown
• Lab tests indicate calibration changed by 0.10.2
  over 6 weeks between calibrations

Standards 338.81 369.39 401.68 431.78
Analyzer Slope Intercept
CADS01 Previous Readings Previous Readings 339.030 369.633 401.940 431.890
CADS01 1.000972 -0.582508 338.772 369.413 401.747 431.727
CADS03 Previous Readings Previous Readings 338.834 369.441 401.743 431.667
CADS03 1.001269 -0.495369 338.768 369.414 401.758 431.719
CADS05 Previous Readings Previous Readings 338.931 369.554 401.882 431.823
CADS05 1.000640 -0.379726 338.771 369.410 401.759 431.719
CADS06 Previous Readings Previous Readings 338.885 369.499 401.809 431.741
CADS06 1.001027 -0.464082 338.769 369.414 401.757 431.720
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Sampling Strategy

• Two levels sampled at each tower
• 100 ft AGL (15 min every hour)
• 360460 ft AGL (45 min every hour)
• Two reference gases
• sampled for 15 min each day(time of day changes)
• Used to post-process calibrated data (if
  necessary)

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Nighttime 100 ft. level
Sunrise
Sunset
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• In-field agreement between sensors first two
  weeks following deployment

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ring2.psu.edu
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ring2.psu.edu
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ring2.psu.edu

• Site specific information
• Latitude
• Longitude
• Installation date
• Sampling heights
• Reference tank information
• Calibration date

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Summary

• Four of five Ring 2 sites installed
• Fifth sites to be installed soon
• Data available near real-time
• Necessary calibration frequency to be determined
• Expected to be monthly
• Network designed to oversample the region
• Will be used to calculate the regional flux for
  comparison with bottom-up methods

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