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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 4, issue 10
Atmos. Meas. Tech., 4, 2093–2103, 2011
https://doi.org/10.5194/amt-4-2093-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Meas. Tech., 4, 2093–2103, 2011
https://doi.org/10.5194/amt-4-2093-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 07 Oct 2011

Research article | 07 Oct 2011

A relaxed eddy accumulation system for measuring vertical fluxes of nitrous acid

X. Ren*,1, J. E. Sanders1, A. Rajendran1,**, R. J. Weber2, A. H. Goldstein2, S. E. Pusede3, E. C. Browne3, K.-E. Min4, and R. C. Cohen4,3 X. Ren et al.
  • 1Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA
  • 2Department of Environmental Science, Policy, and Management, University of California at Berkeley, Berkeley, CA, USA
  • 3Department of Chemistry, University of California at Berkeley, Berkeley, CA, USA
  • 4Department of Earth and Planetary Science, University of California at Berkeley, Berkeley, CA, USA
  • *now at: Air Resources Laboratory, National Oceanic and Atmospheric Administration, Silver Spring, MD, USA
  • **now at: Department of Epidemiology and Public Health, University of Miami, Miami, FL, USA

Abstract. A relaxed eddy accumulation (REA) system combined with a nitrous acid (HONO) analyzer was developed to measure atmospheric HONO vertical fluxes. The system consists of three major components: (1) a fast-response sonic anemometer measuring both vertical wind velocity and air temperature, (2) a fast-response controlling unit separating air motions into updraft and downdraft samplers by the sign of vertical wind velocity, and (3) a highly sensitive HONO analyzer based on aqueous long path absorption photometry that measures HONO concentrations in the updrafts and downdrafts. A dynamic velocity threshold (±0.5σw, where σw is a standard deviation of the vertical wind velocity) was used for valve switching determined by the running means and standard deviations of the vertical wind velocity. Using measured temperature as a tracer and the average values from two field deployments, the flux proportionality coefficient, β, was determined to be 0.42 ± 0.02, in good agreement with the theoretical estimation. The REA system was deployed in two ground-based field studies. In the California Research at the Nexus of Air Quality and Climate Change (CalNex) study in Bakersfield, California in summer 2010, measured HONO fluxes appeared to be upward during the day and were close to zero at night. The upward HONO flux was highly correlated to the product of NO2 and solar radiation. During the Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX 2009) at Blodgett Forest, California in July 2009, the overall HONO fluxes were small in magnitude and were close to zero. Causes for the different HONO fluxes in the two different environments are briefly discussed.

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