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Synonyms: 
Harvard Lyman-α Photofragment Fluorescence Hygrometer
Harvard Water Vapor
Harvard H2O

Harvard and NOAA teams working on their instruments.

MACPEX team members discussing an instrument.

Integrating and Testing Instrument for WB-57

Performing electrical tests on MACPEX Instrument

Presenting Harvard Instrument during TRR

Working on Harvard Instrument

Harvard Lyman-α Photofragment Fluorescence Hygrometer

The Harvard Water Vapor (HWV) instrument combines two independent measurement methods for the simultaneous in situ detection of ambient water vapor mixing ratios in a single duct. This dual axis instrument combines the heritage of the Harvard Lyman-α photo-fragment fluorescence instrument (LyA) with the newly designed tunable diode laser direct absorption instrument (HHH). The Lyman-α detection axis functions as a benchmark measurement, and provides a requisite link to the long measurement history of Harvard Lyman-α aboard NASA’s WB-57 and ER-2 aircraft [Weinstock et al., 1994; Hintsa et al., 1999; Weinstock et al., 2009]. The inclusion of HHH provides a second high precision measurement that is more robust than LyA to changes in its measurement sensitivity [Smith et al., in preparation]. The simultaneous utilization of radically different measurement techniques facilitates the identification, diagnosis, and constraint of systematic errors both in the laboratory and in flight. As such, it constitutes a significant step toward resolving the controversy surrounding water vapor measurements in the upper troposphere and lower stratosphere.

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