A broadband cavity enhanced absorption spectrometer for aircraftmeasurements of glyoxal, methylglyoxal, nitrous acid, nitrogen dioxide, andwater vapor

摘要

We describe a two-channel broadband cavity enhanced absorption spectrometer?(BBCEAS)for aircraft measurements of glyoxal (CHOCHO), methylglyoxal(CH₃COCHO), nitrous acid (HONO), nitrogen dioxide (NO₂), and water(H₂O). The instrument spans 361–389 and 438–468 nm, using twolight-emitting diodes?(LEDs) and a single grating spectrometer with acharge-coupled device?(CCD) detector. Robust performance is achieved using acustom optical mounting system, high-power LEDs with electronic on/offmodulation, high-reflectivity cavity mirrors, and materials that minimizeanalyte surface losses. We have successfully deployed this instrument duringtwo aircraft and two ground-based field campaigns to date. The demonstratedprecision (2σ) for retrievals of CHOCHO, HONO and NO₂ are 34,350, and 80 parts per trillion (pptv) in 5 s. The accuracy is 5.8,9.0, and 5.0 %, limited mainly by the available absorption crosssections.