CAMEX-4 NOAA Lyman-alpha Hygrometer

Total water is measured in situ as vapor with a Lyman-a hygrometer. The ambient sample flows through a closed cell at a high rate to minimize the effect of trapped water. Lyman-a light (121.6 nm) photodissociates water to produce an excited OH radical. The fluorescence from this radical at 309 nm is detected with a phototube and counting system. At aircraft pressures, the fluorescence signal is quenched by air; this gives a signal that is proportional to mixing ratio. The Lyman-alpha hygrometer flew on the NASA ER-2 during CAMEX-4.

(START DATE: 2001-08-16 STOP DATE: 2001-09-25)

NASA Information Contact: Michael Goodman, Global Hydrology and Climate Center
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