An improved fast-response vacuum-UV resonance fluorescence CO instrument

The fast-response resonance fluorescence instrument for the airborne measur ement of carbon monoxide described by Gerbig er al. [1996] was modified by implementing an improved optical filter with more efficient optics and an o ptimized resonance lamp. Besides reductions in size and weight, the new ins trument achieves a sensitivity 10 times higher, a lower background (65 ppb compared with 250 ppb), and a faster time response (<0.1s) than the origina l instrument. The precision is +/-1.5 ppb at an atmospheric mixing ratio of 100 ppb CO, and the detection limit is 3 ppb (2 sigma) for an integration time of 1 s. First results from the North Atlantic Regional Aerosol Charact erization Experiment (ACE-2) campaign during July 1997, when the new instru ment was deployed aboard the U.K. Meteorological Office C-130 aircraft, are used to demonstrate the performance of the new instrument.