Preprints
https://doi.org/10.5194/amt-2022-13
https://doi.org/10.5194/amt-2022-13
 
31 Jan 2022
31 Jan 2022
Status: a revised version of this preprint was accepted for the journal AMT and is expected to appear here in due course.

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

Clare E. Singer1,a, Benjamin Clouser1, Sergey Khaykin2, Martina Krämer3, Francesco Cairo4, Thomas Peter5, Alexey Lykov6, Christian Rolf3, Nicole Spelten3, Simone Brunamonti5,b, and Elisabeth J. Moyer1 Clare E. Singer et al.
  • 1Dept. of the Geophysical Sciences, University of Chicago, Chicago, IL, USA
  • 2LATMOS, UVSQ, Sorbonne Université, CNRS, IPSL, Guyancourt, France
  • 3Forschungszentrum Jülich, Institut für Energie und Klimaforschung (IEK-7), Germany
  • 4National Research Council of Italy, Institute of Atmospheric Sciences and Climate (CNR-ISAC), Rome, Italy
  • 5Institute for Atmospheric and Climate Science, ETH Zürich, Zürich, Switzerland
  • 6Central Aerological Observatory of RosHydroMet, Dolgoprudny, Russian Federation
  • anow at: Dept. of Environmental Science and Engineering, California Institute of Technology, Pasadena, CA, USA
  • bnow at: Empa, Laboratory for Air Pollution/Environmental Technology, Dübendorf, Switzerland

Abstract. 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 differences between ChiWIS and FLASH were only −1.42 % and those between FISH and FLASH only −1.47 %. Agreement between ChiWIS and FLASH for in-cloud conditions is even tighter, at +0.74 %. In general, ChiWIS and FLASH agreed to better than 10 % for 92 % (87 %) of clear-sky (in-cloud) datapoints. Agreement between FISH and FLASH to 10 % occurred in 78 % of clear-sky datapoints. Estimated realized instrumental precision in UTLS conditions was 0.05, 0.1, and 0.2 ppmv for ChiWIS, FISH, and FLASH, 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.

Clare E. Singer et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-13', Anonymous Referee #1, 29 Mar 2022
  • RC2: 'Comment on amt-2022-13', Anonymous Referee #2, 04 Apr 2022
  • RC3: 'Comment on amt-2022-13', Anonymous Referee #3, 08 Apr 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-13', Anonymous Referee #1, 29 Mar 2022
  • RC2: 'Comment on amt-2022-13', Anonymous Referee #2, 04 Apr 2022
  • RC3: 'Comment on amt-2022-13', Anonymous Referee #3, 08 Apr 2022

Clare E. Singer et al.

Clare E. Singer et al.

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Short summary
In situ measurements of water vapor in the upper troposphere are necessary to study cloud formation and hydration of the stratosphere, but challenging due to cold/dry conditions. We compare measurements from three water vapor instruments made during the StratoClim campaign in summer 2017. In clear-sky (clouds), mean differences were < 1.5 % (< 0.8 %). This excellent agreement allows detection of fine-scale structures required to understand the impact of convection on stratospheric water vapor.