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Intercomparison of upper tropospheric and lower stratospheric water vapor measurements over the Asian Summer Monsoon during the StratoClim campaign

Singer, Clare E. and Clouser, Benjamin W. and Khaykin, Sergey M. and Krämer, Martina and Cairo, Francesco and Peter, Thomas and Lykov, Alexey and Rolf, Christian and Spelten, Nicole and Afchine, Armin and Brunamonti, Simone and Moyer, Elisabeth J. (2022) Intercomparison of upper tropospheric and lower stratospheric water vapor measurements over the Asian Summer Monsoon during the StratoClim campaign. Atmospheric Measurement Techniques, 15 (16). pp. 4767-4783. ISSN 1867-8548. doi:10.5194/amt-15-4767-2022.

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In situ measurements in the climatically important upper troposphere–lower stratosphere (UTLS) are critical for understanding controls on cloud formation, the entry of water into the stratosphere, and hydration–dehydration of the tropical tropopause layer. Accurate in situ measurement of water vapor in the UTLS however is difficult because of low water vapor concentrations (<5 ppmv) and a challenging low temperature–pressure environment. The StratoClim campaign out of Kathmandu, Nepal, in July and August 2017, which made the first high-altitude aircraft measurements in the Asian Summer Monsoon (ASM), also provided an opportunity to intercompare three in situ hygrometers mounted on the M-55 Geophysica: ChiWIS (Chicago Water Isotope Spectrometer), FISH (Fast In situ Stratospheric Hygrometer), and FLASH (Fluorescent Lyman-α Stratospheric Hygrometer). Instrument agreement was very good, suggesting no intrinsic technique-dependent biases: ChiWIS measures by mid-infrared laser absorption spectroscopy and FISH and FLASH by Lyman-α induced fluorescence. In clear-sky UTLS conditions (H2O<10 ppmv), mean and standard deviations of differences in paired observations between ChiWIS and FLASH were only (-1.4±5.9) % and those between FISH and FLASH only (-1.5±8.0) %. Agreement between ChiWIS and FLASH for in-cloud conditions is even tighter, at (+0.7±7.6) %. Estimated realized instrumental precision in UTLS conditions was 0.05, 0.2, and 0.1 ppmv for ChiWIS, FLASH, and FISH, respectively. This level of accuracy and precision allows the confident detection of fine-scale spatial structures in UTLS water vapor required for understanding the role of convection and the ASM in the stratospheric water vapor budget.

Item Type:Article
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URLURL TypeDescription Article
Singer, Clare E.0000-0002-1708-0997
Khaykin, Sergey M.0000-0002-5466-1096
Krämer, Martina0000-0002-2888-1722
Rolf, Christian0000-0001-5329-0054
Afchine, Armin0000-0002-7669-8295
Additional Information:Acknowledgements. We gratefully thank the StratoClim coordination team and the Myasishchev Design Bureau for successfully conducting the field campaign. We also thank the three anonymous referees for their constructive remarks. Financial support. This research has been supported by the Seventh Framework Programme (STRATOCLIM (grant no. 603557)) and NSF grant no. 1743753 to Elisabeth J. Moyer. Clare E. Singer was additionally supported by a UChicago Summer Undergraduate Research Fellowship.
Funding AgencyGrant Number
Seventh Framework Programme603557
University of ChicagoSummer Undergraduate Research Fellowship
Issue or Number:16
Record Number:CaltechAUTHORS:20220829-467858200
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116618
Deposited By: Donna Wrublewski
Deposited On:22 Sep 2022 19:22
Last Modified:22 Sep 2022 19:22

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