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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 5, issue 10 | Copyright
Atmos. Meas. Tech., 5, 2329-2338, 2012
© Author(s) 2012. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 01 Oct 2012

Research article | 01 Oct 2012

Consistency of long-term elemental carbon trends from thermal and optical measurements in the IMPROVE network

L.-W. A. Chen2,1, J. C. Chow2,1, J. G. Watson2,1, and B. A. Schichtel3 L.-W. A. Chen et al.
  • 1Division of Atmospheric Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, Nevada 89512, USA
  • 2State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, 10 Fenghui South Road, Xi'an 710075, China
  • 3Cooperative Institute for Research in the Atmosphere, Colorado State University, 1375 Campus Delivery, Fort Collins, Colorado 80523, USA

Abstract. Decreasing trends of elemental carbon (EC) have been reported at US Interagency Monitoring of PROtected Visual Environments (IMPROVE) network from 1990 to 2004, consistent with the phase-in of cleaner engines, residential biomass burning technologies, and prescribed burning practices. EC trends for the past decade are examined due to an upgrade of IMPROVE carbon instruments and the thermal/optical analysis protocol since 2005. Filter reflectance (τR) values measured as part of the carbon analysis were retrieved from archived data and compared with EC for 65 sites with more complete records within 2000–2009. EC–τR relationships suggest minor changes of EC quantified by the original and upgraded instruments for most IMPROVE samples. EC and τR show universal decreasing trends across the US. The EC and τR trends are correlated, with national average downward rates (relative to the 2000–2004 baseline medians) of 4.5% yr−1 for EC and 4.1% yr−1 for τR. The consistency between independent EC and τR measurements adds to the weight of evidence that EC reductions are real rather than an artifact of changes to the measurement process.

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