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The airborne mass spectrometer AIMS – Part 1: AIMS-H2O for UTLS water vapor measurements

Kaufmann, Stefan and Voigt, Christiane and Jurkat, Tina and Thornberry, Troy and Fahey, David W. and Gao, Ru-Shan and Schlage, Romy and Schäuble, Dominik and Zöger, Martin (2016) The airborne mass spectrometer AIMS – Part 1: AIMS-H2O for UTLS water vapor measurements. Atmospheric Measurement Techniques (AMT) (9), pp. 939-953. Copernicus Publications. DOI: 10.5194/amt-9-939-2016 ISSN 1867-1381

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Official URL: http://www.atmos-meas-tech.net/9/939/2016/

Abstract

In the upper troposphere and lower stratosphere (UTLS), the accurate quantification of low water vapor concentrations has presented a significant measurement challenge. The instrumental uncertainties are passed on to estimates of H2O transport, cloud formation and the role of H2O in the UTLS energy budget and resulting effects on surface temperatures. To address the uncertainty in UTLS H2O determination, the airborne mass spectrometer AIMS-H2O, with in-flight calibration, has been developed for fast and accurate airborne water vapor measurements. We present a new setup to measure water vapor by direct ionization of ambient air. Air is sampled via a backward facing inlet that includes a bypass flow to assure short residence times (< 0.2 s) in the inlet line, which allows the instrument to achieve a time resolution of  ∼ 4 Hz, limited by the sampling frequency of the mass spectrometer. From the main inlet flow, a smaller flow is extracted into the novel pressure-controlled gas discharge ion source of the mass spectrometer. The air is directed through the gas discharge region where ion–molecule reactions lead to the production of hydronium ion clusters, H3O+(H2O)n (n = 0, 1, 2), in a complex reaction scheme similar to the reactions in the D-region of the ionosphere. These ions are counted to quantify the ambient water vapor mixing ratio. The instrument is calibrated during flight using a new calibration source based on the catalytic reaction of H2 and O2 on a Pt surface to generate a calibration standard with well-defined and stable H2O mixing ratios. In order to increase data quality over a range of mixing ratios, two data evaluation methods are presented for lower and higher H2O mixing ratios respectively, using either only the H3O+(H2O) ions or the ratio of all water vapor dependent ions to the total ion current. Altogether, a range of water vapor mixing ratios from 1 to 500 parts per million by volume (ppmv) can be covered with an accuracy between 7 and 15 %. AIMS-H2O was deployed on two DLR research aircraft, the Falcon during CONCERT (CONtrail and Cirrus ExpeRimenT) in 2011, and HALO during ML-CIRRUS (Mid-Latitude CIRRUS) in 2014. The comparison of AIMS-H2O with the SHARC tunable diode laser hygrometer during ML-CIRRUS shows a correlation near to 1 in the range between 10 and 500 ppmv for the entire campaign.

Item URL in elib:https://elib.dlr.de/105394/
Document Type:Article
Title:The airborne mass spectrometer AIMS – Part 1: AIMS-H2O for UTLS water vapor measurements
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Kaufmann, StefanDLR, IPAUNSPECIFIED
Voigt, ChristianeDLR, IPAUNSPECIFIED
Jurkat, TinaDLR, IPAUNSPECIFIED
Thornberry, TroyNOAA, Boulder, CO, USAUNSPECIFIED
Fahey, David W.NOAA, Boulder, CO, USAUNSPECIFIED
Gao, Ru-ShanNOAA, Boulder, CO, USAUNSPECIFIED
Schlage, RomyDLR, IPAUNSPECIFIED
Schäuble, DominikDLR, IPAUNSPECIFIED
Zöger, MartinDLR, FXUNSPECIFIED
Date:7 March 2016
Journal or Publication Title:Atmospheric Measurement Techniques (AMT)
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
DOI :10.5194/amt-9-939-2016
Page Range:pp. 939-953
Publisher:Copernicus Publications
ISSN:1867-1381
Status:Published
Keywords:mass spectrometry, water vapor, airborne measurements
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Erdbeobachtung
DLR - Research theme (Project):R - Project Climatic relevance of atmospheric tracer gases, aerosols and clouds
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Trace Species
Flugexperimente
Deposited By: Kaufmann, Stefan
Deposited On:26 Jul 2016 09:26
Last Modified:08 Mar 2018 18:10

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