Electrochemical concentration cell (ECC) ozonesonde pump efficiency measurements
and tests on the sensitivity to ozone of buffered and unbuffered ECC sensor
cathode solutions
Bryan J. Johnson, Samuel J. Oltmans, and Holger Vömel
Climate Monitoring and Diagnostics Laboratory, National Oceanic and Atmospheric
Administration, Boulder, Colorado, USA
Herman G. J. Smit
Institute for Chemistry of the Polluted Atmosphere (ICG-2), Research Center
Jülich, Germany
Terry Deshler and Chris Kröger
Department of Atmospheric Science, University of Wyoming, Laramie, Wyoming,
USA
Abstract. On the basis of extensive laboratory and field tests of electrochemical
concentration cell (ECC) ozonesondes, a height-dependent artifact in ozone
profile measurements was found that is primarily due to side reactions
of the phosphate buffers used in the ‘‘standard’’ 1% potassium iodide sensing
solution. The influence of the buffers was revealed as a result of new,
direct measurements of the ozonesonde pump flow rate efficiency made in
an environmental chamber using an oil bubble flowmeter developed at National
Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics
Laboratory (NOAA/CMDL). The new flow rate measurements give pump efficiency
correction factors that are 2 and 15% greater at 100 and 5 hPa, respectively,
than those used in currently recommended procedures. Profile measurements
using ozonesondes with differing ECC sensor solutions, on dual-sonde balloons
and experiments in a simulation chamber, show that the impact of the buffers
is most pronounced above the ozone partial pressure maximum. The effect
is about a 10–15% overmeasurement of ozone at an altitude of 30 km. Careful
consideration must be given to the combination of the sensing solution
composition and pump efficiency correction if representative ozone profiles
are to be obtained from ozonesonde measurements.
J Geophysical Res., 10.1029/2001JD000557