Title: "Ring%202":
1"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
2The 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.
3ChEAS 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.
4Mid-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.
5The 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
6Ring 2 sites
-
- Kewanee, IL
- Centerville, IA
- Mead, NE
- Round Lake, MN
- Highland, WI
7Round 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
8Cavity 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
9Cavity 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
10Predeployment 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
11Cavity 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
12Sampling 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)
13Nighttime 100 ft. level
Sunrise
Sunset
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15- In-field agreement between sensors first two
weeks following deployment
16ring2.psu.edu
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18ring2.psu.edu
- Site specific information
- Latitude
- Longitude
- Installation date
- Sampling heights
- Reference tank information
- Calibration date
19Summary
- 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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