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On the Accuracy of In Situ Water Vapor Measurements in the Troposphere and Lower Stratosphere with the Harvard Lyman-Alpha HygrometerIn an effort to better constrain atmospheric water vapor mixing ratios and to understand the discrepancies between different measurements of water vapor in the stratosphere and troposphere, we have carefully examined data from the Harvard Lyman-alpha photofragment fluorescence hygrometer, which has flown on the NASA ER-2 aircraft from 1992 through 1998. The instrument is calibrated in the laboratory before and after each deployment, and the calibration is checked by direct absorption measurements in the troposphere. On certain flights, the ER-2 flew level tracks during which water vapor varied by up to 80 ppmv, under nearly constant atmospheric conditions. These flights provide a stringent test of our calibration via direct absorption and indicate agreement to within 3%. During the 1997 Photochemistry of Ozone Loss in the Arctic Region In Summer (POLARIS) mission, our Lyman-alpha instrument was compared with a new diode laser hygrometer from the Jet Propulsion Laboratory. Overall agreement was 5% during the June/July deployment and 1% for potential temperatures of 490 to 540 K. The accuracy of our instrument is shown to be +/-5 %, with an additional offset of at most 0.1 ppmv. Data from this instrument, combined with simultaneous measurements of CH4, and H2, are therefore ideal for studies of the hydrogen budget of the lower stratosphere.
Document ID
20010062627
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Hintsa, Eric J.
(Harvard Univ. Cambridge, MA United States)
Weinstock, Elliot M.
(Harvard Univ. Cambridge, MA United States)
Anderson, James G.
(Harvard Univ. Cambridge, MA United States)
May, Randy D.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Hurst, Dale F.
(National Oceanic and Atmospheric Administration Boulder, CO United States)
Date Acquired
August 20, 2013
Publication Date
April 20, 1999
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 104
Issue: D7
ISSN: 0148-0227
Subject Category
Geophysics
Report/Patent Number
Paper-1998JD100110
Funding Number(s)
CONTRACT_GRANT: NCC2-913
Distribution Limits
Public
Copyright
Other

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