A new non-resonant laser-induced fluorescence instrument for the airborne in situ measurement of formaldehyde

Abstract

Abstract. A new in situ instrument for gas-phase formaldehyde (HCHO), COmpact Formaldehyde FluorescencE Experiment (COFFEE), is presented. COFFEE utilizes nonresonant laser-induced fluorescence (NR-LIF) to measure HCHO, with 300 mW of 40 kHz 355 nm laser output exciting multiple HCHO absorption features. The resulting HCHO fluorescence is collected at 5 ns resolution, and the fluorescence time profile is fit to yield the ambient HCHO mixing ratio. Typical 1σ precision at ∼ 0 pptv HCHO is 150 pptv for 1 s data. The compact instrument was designed to operate with minimal in-flight operator interaction and infrequent maintenance (1-2 times per year). COFFEE fits in the wing pod of the Alpha Jet stationed at the NASA Ames Research Center and has successfully collected HCHO data on 27 flights through 2017 March. The frequent flights, combined with a potentially long-term data set, makes the Alpha Jet a promising platform for validation of satellite-based column HCHO.

Intercomparison of lidar, aircraft, and surface ozone measurements in the San Joaquin Valley during the California Baseline Ozone Transport Study (CABOTS)

“…The Alpha Jet carried an external wing pod with a modified commercial UV absorption monitor (2B Technologies Inc., model 205) to measure O 3 (Ryoo et al, 2017;Yates et al, 2013Yates et al, , 2015 and a (Picarro model 2301 m) cavity ringdown analyzer to measure CO 2 , CH 4 , and H 2 O . A second wing pod carried a nonresonant laserinduced fluorescence instrument to measure formaldehyde (CH 2 O) (St. Clair et al, 2017). The pod mounting kept the residence times of the sample inlets to less than 2 s. The air-craft is also equipped with GPS and inertial navigation systems to provide altitude and position information, and the NASA Ames-developed meteorological measurement systems to provide highly accurate pressure, temperature, and 3-D wind data.…”

A new laser-based and ultra-portable gas sensor for indoor and outdoor formaldehyde (HCHO) monitoring

“…During a HCHO multi-hour intercomparison performed at NASA Goddard in November 2017, the Aeris sensor was operated in HDO mode in the laboratory and compared against two NASA LIF instruments: NASA ISAF (In Situ Airborne Formaldehyde; Cazorla et al, 2015) and NASA CAFE (Compact Airborne Formaldehyde Experiment; operating principle described in St. Clair et al, 2017, 2019.…”

CAFE: a new, improved non-resonant laser-induced fluorescence instrument for airborne in situ measurement of formaldehyde

“…2, item K). The optical filters for the two detection axes differ from each other and from the filters 25 described in St. Clair et al, 2017.…”

“…The primary motivation for the change in filters from St. Clair et al, 2017 was the realization that H2O Raman signal, at high [H2O], adversely affected data processing as discussed in the Supplement (Fig.…”

“…The different techniques offer trade-offs between cost, instrument size, sampling time resolution, and sensitivity. A new approach, non-resonant LIF (NR-LIF), was recently developed to provide a more compact, lower cost instrument with simpler operation than typical HCHO LIF instruments (St. Clair et al, 2017). The NR-LIF approach trades the wavelength-tunable excitation laser traditionally 10 used in HCHO LIF for a fixed wavelength 355 nm laser that excites multiple HCHO absorption features.…”