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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 3, issue 2
Atmos. Meas. Tech., 3, 495–505, 2010
https://doi.org/10.5194/amt-3-495-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Meas. Tech., 3, 495–505, 2010
https://doi.org/10.5194/amt-3-495-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  29 Apr 2010

29 Apr 2010

Ozone sonde cell current measurements and implications for observations of near-zero ozone concentrations in the tropical upper troposphere

H. Vömel1,* and K. Diaz2 H. Vömel and K. Diaz
  • 1University of Colorado, Boulder, CO, USA
  • 2National Center for Atmospheric Research, Significant Opportunities in Atmospheric Research and Science Program, Boulder, CO, USA
  • *now at: Deutscher Wetterdienst, Meteorological Observatory Lindenberg, Germany

Abstract. Laboratory measurements of the Electrochemical Concentration Cell (ECC) ozone sonde cell current using ozone free air as well as defined amounts of ozone reveal that background current measurements during sonde preparation are neither constant as a function of time, nor constant as a function of ozone concentration. Using a background current, measured at a defined timed after exposure to high ozone may often overestimate the real background, leading to artificially low ozone concentrations in the upper tropical troposphere, and may frequently lead to operator dependent uncertainties. Based on these laboratory measurements an improved cell current to partial pressure conversion is proposed, which removes operator dependent variability in the background reading and possible artifacts in this measurement. Data from the Central Equatorial Pacific Experiment (CEPEX) have been reprocessed using the improved background treatment based on these laboratory measurements. In the reprocessed data set near-zero ozone events no longer occur. At Samoa, Fiji, Tahiti, and San Cristóbal, nearly all near-zero ozone concentrations occur in soundings with larger background currents. To a large extent, these events are no longer observed in the reprocessed data set using the improved background treatment.

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