The airborne mass spectrometer AIMS – Part 1: AIMS-H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O for UTLS water vapor measurements

Kaufmann, Stefan H. E.; Voigt, Christiane; Jurkat, Tina; Thornberry, T. D.; Fahey, D. W.; Gao, R. S.; Schlage, Romy; Schäuble, Dominik; Zöger, Martin

doi:10.5194/amt-9-939-2016

Cited by 31 publications

(34 citation statements)

References 47 publications

(44 reference statements)

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“…Detailed descriptions about the measurement strategy and uncertainties in the data processing are discussed in Afchine et al (2017). IWC is derived from the difference between the amount of total enhanced water (H 2 O tot ) and the amount of gas-phase water (H 2 O gas ) (Kaufmann et al, 2016). Due to the enhancement factor (Voigt et al, 2006) at the HALO-TGI, which is about 20-35, the minimum detectable IWC is in the range between 1 and 2000 ppm (1-2000 × 10 −2 mg m −3 ).…”

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confidence: 99%

Comparing airborne and satellite retrievals of cloud optical thickness and particle effective radius using a spectral radiance ratio technique: two case studies for cirrus and deep convective clouds

et al. 2018

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Abstract. Solar radiation reflected by cirrus and deep convective clouds (DCCs) was measured by the Spectral Modular Airborne Radiation Measurement System (SMART) installed on the German High Altitude and Long Range Research Aircraft (HALO) during the Mid-Latitude Cirrus (ML-CIRRUS) and the Aerosol, Cloud, Precipitation, and Radiation Interaction and Dynamic of Convective Clouds System -Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modelling and to the Global Precipitation Measurement (ACRIDICON-CHUVA) campaigns. On particular flights, HALO performed measurements closely collocated with overpasses of the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard the Aqua satellite. A cirrus cloud located above liquid water clouds and a DCC topped by an anvil cirrus are analyzed in this paper. Based on the nadir spectral upward radiance measured above the two clouds, the optical thickness τ and particle effective radius r eff of the cirrus and DCC are retrieved using a radiance ratio technique, which considers the cloud thermodynamic phase, the vertical profile of cloud microphysical properties, the presence of multilayer clouds, and the heterogeneity of the surface albedo. For the cirrus case, the comparison of τ and r eff retrieved on the basis of SMART and MODIS measurements yields a normalized mean absolute deviation of up to 1.2 % for τ and 2.1 % for r eff . For the DCC case, deviations of up to 3.6 % for τ and 6.2 % for r eff are obtained. The larger deviations in the DCC case are mainly attributed to the fast cloud evolution and three-dimensional (3-D) radiative effects. Measurements of spectral upward radiance at near-infrared wavelengths are employed to investigate the vertical profile of r eff in the cirrus. The retrieved values of r eff are compared with corresponding in situ measurements using a vertical weighting method. Compared to the MODIS observations, measurements of SMART provide more information on the vertical distribution of particle sizes, which allow reconstructing the profile of r eff close to the cloud top. The comparison between retrieved and in situ r eff yields a normalized mean absolute deviation, which ranges between 1.5 and 10.3 %, and a robust correlation coefficient of 0.82.

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Comparing airborne and satellite retrievals of cloud optical thickness and particle effective radius using a spectral radiance ratio technique: two case studies for cirrus and deep convective clouds

et al. 2018

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“…The Arctic polar vortex during the winter 2015/2016 has already been subject to a number of studies, most of them directly related to POLSTRACC activities. Overviews of the evolution of the polar vortex are given by Manney and Lawrence (2016), Matthias et al (2016) and Khosrawi et al (2017) including satellite, reanalysis and model perspectives. Concurrently, the authors point out the exceptional strength of the vortex due to reduced planetary wave activity, accompanied by record low temperatures and extensive denitrification, dehydration and chlorine activation.…”

Section: Activities Within the Polstracc Missionmentioning

confidence: 99%

“…This is the consequence of unresolved transport of ozone and counteracting effects from catalytic depletion and stratospheric cooling during climate change, where some transport and chemical processes may not have been implemented into the models in complete detail. In particular, Khosrawi et al (2017) have shown recently that the climate model ECHAM5/MESSy Atmospheric Chemistry (EMAC) underestimates stratospheric downward transport in the polar vortex and potentially inherits uncertainties in chlorine chemistry kinetics. The lack of observations inside the polar LMS may contribute to the enhanced uncertainty.…”

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Chlorine partitioning in the lowermost Arctic vortex during the cold winter 2015/2016

Marsing

Jurkat‐Witschas

Grooß³

et al. 2019

Atmos. Chem. Phys.

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Activated chlorine compounds in the polar winter stratosphere drive catalytic cycles that deplete ozone and methane, whose abundances are highly relevant to the evolution of global climate. The present work introduces a novel dataset of in situ measurements of relevant chlorine species in the lowermost Arctic stratosphere from the aircraft mission POLSTRACC-GW-LCYCLE-SALSA during winter 2015/2016. The major stages of chemical evolution of the lower polar vortex are presented in a consistent series of high-resolution mass spectrometric observations of HCl and ClONO 2 . Simultaneous measurements of CFC-12 are used to derive total inorganic chlorine (Cl y ) and active chlorine (ClO x ). The new data highlight an altitude dependence of the pathway for chlorine deactivation in the lowermost vortex with HCl dominating below the 380 K isentropic surface and ClONO 2 prevailing above. Further, we show that the Chemical Lagrangian Model of the Stratosphere (CLaMS) is generally able to reproduce the chemical evolution of the lower polar vortex chlorine budget, except for a bias in HCl concentrations. The model is used to relate local measurements to the vortex-wide evolution. The results are aimed at fostering our understanding of the climate impact of chlorine chemistry, providing new observational data to complement satellite data and assess model performance in the climatesensitive upper troposphere and lower stratosphere region.

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“…As a consequence, novel concepts and instruments (e.g. Thornberry et al, 2013;Kaufmann et al, 2014;Kaufmann et al, 2016;Buchholz et al, 2017) and improved techniques for inflight (Rollins et al, 2011) and ground calibration (Meyer et al, 2015) were developed to improve the accuracy of H 2 O measurements.…”

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confidence: 99%

Intercomparison of mid-latitude tropospheric and lower stratospheric water vapor measurements and comparison to ECMWF humidity data

Kaufmann¹,

Voigt²,

Heller³

et al. 2018

Preprint

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Abstract. Accurate measurement of water vapor in the climate sensitive region near the tropopause turned out to be very challenging. Unexplained systematic discrepancies between measurements at low water vapor mixing ratios made by different instruments on airborne platforms have limited our ability to adequately address a number relevant scientific questions on the humidity distribution, cloud formation and climate impact in that region. Therefore, during the past decade, the scientific community has undertaken substantial efforts to understand these discrepancies and improve the quality of 20 water vapor measurements. This study presents a comprehensive intercomparison of airborne state-of-the-art in situ hygrometers deployed onboard the DLR (German Aerospace Center) research aircraft HALO during the Mid-Latitude CIRRUS (ML-CIRRUS) campaign conducted in 2014 over central Europe. The instrument intercomparison shows that the hygrometer measurements agree within their combined accuracy (±10 to 15%, depending on the humidity regime), total mean values even agree within 2.5%. However, systematic differences on the order of 10% and up to a maximum of 15% are 25 found for mixing ratios below 10 parts per million (ppm) H 2 O. A comparison of relative humidity within cirrus clouds does not indicate a systematic instrument bias in either water vapor or temperature measurements in the upper troposphere.Furthermore, in situ measurements are compared to model data from the European Centre for Medium-Range Weather Forecasts (ECMWF) which are interpolated along the ML-CIRRUS flight tracks. We find a mean agreement within ±10% throughout the troposphere and a significant wet bias in the model on the order of 100% to 150% in the stratosphere close to 30 the tropopause. Consistent with previous studies, this analysis indicates that the model deficit is mainly caused by a blurred humidity gradient at tropopause altitudes.Atmos. Chem. Phys. Discuss., https://doi

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The airborne mass spectrometer AIMS – Part 1: AIMS-H<sub>2</sub>O for UTLS water vapor measurements

Cited by 31 publications

References 47 publications

Comparing airborne and satellite retrievals of cloud optical thickness and particle effective radius using a spectral radiance ratio technique: two case studies for cirrus and deep convective clouds

Comparing airborne and satellite retrievals of cloud optical thickness and particle effective radius using a spectral radiance ratio technique: two case studies for cirrus and deep convective clouds

Chlorine partitioning in the lowermost Arctic vortex during the cold winter 2015/2016

Intercomparison of mid-latitude tropospheric and lower stratospheric water vapor measurements and comparison to ECMWF humidity data

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