Showing papers by "James Walega published in 1991"

Compact measurement system for the simultaneous determination of NO, NO2, NOy, and O3 using a small aircraft

Abstract: A high performance measurement system based upon NO/03 chemiluminescence has been developed for simultaneous measurements of the title species using smaller aircraft such as the NCAR Sabreliner. NO is determined directly, NO2 Is converted to NO by broad-band photolysis, NOy i5converted to NO using gold-catalysed reduction in the presence of CO, and 03 5 determined using excess NO as the reagent. The system is capable of measurements of the odd nitrogen species at levels below 10 pptv. A description of the instrument and its application to some flights within a thunderstorm are presented. INTRODUCTION An Important fraction of the tropospheric concentration of 03 IS currently believed to result from photochemical production In situ.' Active odd nitrogen NOx (N0 + NO2) and CO orhydrocarbons are essential for 03 formation but in many regions of the troposphere this photochemical production is limited by the availability of NOx. Thus an understanding of the budget of tropospheric 03 or Its possible trends relies upon detailed knowledge of the sources, sinks,