A laser-induced fluorescence instrument for aircraft measurements of sulfur dioxide in the upper troposphere and lower stratosphere

Abstract

Abstract. This work describes the development and testing of a new instrument for in situ measurements of sulfur dioxide (SO 2 ) 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 SO 2 at 216.9 nm. Sensitivity and background checks are achieved in flight by additions of SO 2 calibration gas and zero air, respectively. Aircraft demonstration was performed during the NASA VolcanoPlume 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 SO 2 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).

The role of sulfur dioxide in stratospheric aerosol formation evaluated by using in situ measurements in the tropical lower stratosphere

“…An in situ instrument based on a laser‐induced fluorescence (LIF) technique was used in this study to achieve the desired sensitivity for SO 2 mixing ratios on the order of 1 part per trillion (pptv, 10 −12 number mixing ratio) and to afford operation onboard the NASA WB‐57F high‐altitude research aircraft [ Rollins et al , ]. The instrument excites SO 2 by using a tunable laser near 216.9 nm and detects the resulting red‐shifted fluorescence at 240–400 nm.…”

Flight Deployment of a High‐Resolution Time‐of‐Flight Chemical Ionization Mass Spectrometer: Observations of Reactive Halogen and Nitrogen Oxide Species

“…SO 2 is removed from the atmosphere primarily by homogeneous and heterogeneous oxidation with a characteristic lifetime of one to two days (Langner & Rodhe, 1991;Wojcik & Chang, 1997) to form sulfuric acid (H 2 SO 4 ) and sulfate (SO 4 2À ), therefore, contributing to new particle formation (Sipila et al, 2010) as well as the acidity of precipitation (Hegg & Hobbs, 1981) and aerosols (Weber et al, 2016). SO 2 as well has been measured extensively by mass spectrometry (Huey et al, 1995Jurkat et al, 2010;Kim et al, 2007;Miake-Lye et al, 1998;Mohler et al, 1992;Seeley et al, 1997;Slusher et al, 2004;Speidel et al, 2007;Thornton et al, 2002) but is most commonly measured utilizing fluorescence (Luke, 1997;Matsumi et al, 2005;Okabe et al, 1973;Rollins et al, 2016;Schwarz et al, 1974;Simeonsson et al, 2012).…”

Single-photon laser-induced fluorescence detection of nitric oxide at sub-parts per trillion mixing ratios

“…Since the pulse-pair resolution is greater than the signal lifetime the system will at most count one fluorescent photon per laser shot and therefore at very high signal levels the observed count rate will start to deviate from a linear response to the rate at which photons strike the photocathode. However, as discussed previously (Wennberg et al, 1994;Rollins et al, 2016) under the conditions of a known maximum count rate (320 kHz) the observed count rate can be corrected exactly to match the true signal rate and thereby significantly increase the dynamic range without loss of accuracy. At the present typical signal rates (∼ 10 counts s −1 pptv −1 ), errors associated with saturation would not be encountered for NO less than 100 ppbv.…”

“…The laser and optical detection system used here are based on that originally described by Rollins et al (2016) for measurements of sulfur dioxide. Subsequent to that work, important changes have been made to the design of the fiber laser system, and therefore a complete description is provided here.…”