A laser-induced fluorescence instrument for aircraft measurements of sulfur
dioxide in the upper troposphere and lower stratosphere
Andrew W. Rollins1,2,Troy D. Thornberry1,2,Steven J. Ciciora2,Richard J. McLaughlin1,2,Laurel A. Watts1,2,Thomas F. Hanisco3,Esther Baumann4,Fabrizio R. Giorgetta4,Thaopaul V. Bui5,David W. Fahey1,2,and Ru-Shan Gao2Andrew W. Rollins et al.Andrew W. Rollins1,2,Troy D. Thornberry1,2,Steven J. Ciciora2,Richard J. McLaughlin1,2,Laurel A. Watts1,2,Thomas F. Hanisco3,Esther Baumann4,Fabrizio R. Giorgetta4,Thaopaul V. Bui5,David W. Fahey1,2,and Ru-Shan Gao2
Received: 04 May 2016 – Discussion started: 19 May 2016 – Revised: 06 Aug 2016 – Accepted: 25 Aug 2016 – Published: 20 Sep 2016
Abstract. This work describes the development and testing of a new instrument for in situ measurements of sulfur dioxide (SO2) on airborne platforms in the upper troposphere and lower stratosphere (UT–LS). The instrument is based on the laser-induced fluorescence technique and uses the fifth harmonic of a tunable fiber-amplified semiconductor diode laser system at 1084.5 nm to excite SO2 at 216.9 nm. Sensitivity and background checks are achieved in flight by additions of SO2 calibration gas and zero air, respectively. Aircraft demonstration was performed during the NASA Volcano-Plume Investigation Readiness and Gas-Phase and Aerosol Sulfur (VIRGAS) experiment, which was a series of flights using the NASA WB-57F during October 2015 based at Ellington Field and Harlingen, Texas. During these flights, the instrument successfully measured SO2 in the UT–LS at background (non-volcanic) conditions with a precision of 2 ppt at 10 s and an overall uncertainty determined primarily by instrument drifts of ±(16 % + 0.9 ppt).
In situ measurements of SO2 in the tropical UT–LS have been scarce, in part due to limitations of existing instrumentation. Here we present a new laser-induced fluorescence instrument capable of measuring SO2 in the UT–LS region at single part-per-trillion (ppt) mixing ratios and demonstrate it on the NASA WB-57F aircraft up to 19.7 km altitude.
In situ measurements of SO2 in the tropical UT–LS have been scarce, in part due to limitations...
