Two Automated Ozone Analyzers for Use on Civil Aircraft Operating in the Tropopause Region

Abstract

Within the CARIBIC (Civil Aircraft for Regular Investigation of the Atmosphere Based on an Instrument Container) project, deployment of an automated container with analytical equipment for the observation of atmospheric trace gases and aerosols in the tropopause region allows a systematic collection of relevant data at comparatively low costs. Two ozone analyzers for simultaneous operation in the CARIBIC container during long-distance flights were developed for high-altitude measurements. Typical cruising altitudes during long-distance flights of about 10?000 km are in the range of 10?12 km. The design and characteristics of the two instruments, a fast-response ozone sensor, OSCAR (Ozone Sensor CARIBIC), based on a dry chemiluminescence technique; and a modified UV absorption ozone analyzer, OMCAL (Ozone Monitor Calibrator), are described. While OSCAR with a time resolution of 10 Hz can measure changes in ozone concentration at cruising altitudes on a horizontal scale of about 30 m, OMCAL with a time resolution of 17 s (?4.2 km flight distance) serves as a calibrator for the ozone concentrations measured by OSCAR. Having two ozone analyzers with different detection methods eliminates measurement artifacts in the harsh environment of the tropopause region. The results of laboratory tests under high-altitude conditions as well as aircraft measurements of atmospheric ozone in the tropopause region are presented.