Jens-Christopher Mayer

Preparation Methods to Optimize the Performance of Sensor Discs for Fast Chemiluminescence Ozone Analyzers

Fast ozone (O(3)) measurements (1-50 Hz) in the atmosphere are required for airborne studies and for the measurement of ground-based O(3) fluxes by the eddy covariance technique. Fast response analyzers, based on heterogeneous chemiluminescence, need dye coated sensor discs on which the chemiluminescence is generated. In this study, we present three new preparation methods for those sensor discs. Currently available sensor discs exhibit a fast temporal decay of sensitivity, resulting in short duty times which is troublesome for many field applications. To produce sensor discs that provide more stable signals over time, three dyes and nine energy transfer reagents were tested (as well as different stoichiometric mixtures). The resulting optimal method saves 80% of the solid chemicals and shows a duty ozone dose that is prolonged by a factor of 3.5, revealing the same average sensitivity as currently available discs. In addition, we observed a strong effect of the adsorption matrix on the O(3) sensitivity, although silica discs from the same manufacturer were used. Application of the new sensor discs during field measurements showed that the results are consistent with the laboratory data.

Moving measurement platforms - specific challenges and corrections

Most sensors do not perfectly reproduce changes of the measured quantity with respect to time and intensity. Delays and damping effects cause the signal to deviate from the true value. These deviations are often caused by combined impacts of the probe itself, the probe’s housing, the sensor’s inlet system and more. In this work, we will (a) evaluate correction schemes already known from aircraft temperature measurements for their performance on measured vertical temperature profiles, and (b) present an alternative, simpler correction scheme. The temperature profiles were measured with an elevator system at a 99 m mast from 2 m to 98 m a.g.l., parallel to a stationary high quality reference temperature profile. Besides laboratory tests, we will demonstrate and quantify the effect of the corrections applied to the mobile temperature sensor’s data in direct comparison with the reference temperature data. This direct comparison (a) exceeds the potential of aircraft measurements, where comparisons with stationary in-situ sensors are hard to realize, and (b) clearly shows the effectiveness and correct magnitude of the corrections. It is demonstrated with temperature measurements, that a mobile sensor can satisfactorily substitute a profile of stationary sensors. Zusammenfassung