Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2017-308
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
05 May 2017
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Analyzing trace gas filaments in the Ex-UTLS by 4D-variational assimilation of airborne tomographic retrievals
Annika Vogel1,2, Jörn Ungermann3, and Hendrik Elbern1,2 1Rhenish Institute for Environmental Research at the University of Cologne, Germany
2Institute for Energy and Climate Research - Troposphere (IEK-8), Forschungszentrum Jülich, Germany
3Institute for Energy and Climate Research - Stratosphere (IEK-7), Forschungszentrum Jülich, German
Abstract. This case study explores the potential for chemical state analysis at extratropical upper tropospheric – lower stratospheric (Ex-UTLS) height levels with airborne limb-images, assimilated into an advanced spatio-temporal system. The investigation is motivated by the limited capability of both, nadir- and limb-viewing satellite sensors to resolve highly filamented structures, delineated by sharp trace gas gradients on small horizontal and vertical scales. The EURAD-IM (EURopean Air pollution Dispersion – Inverse Model) is applied as assimilation system and designed to extend the flight path confined retrievals from GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) to both, larger areas and detailed vertical structures by a tomographic flight pattern. Related potential and limitations of the method are studied with the following features applied: (i) airborne limb-imaging observations of the Ex-UTLS, (ii) spatio-temporal extension by 4-dimensional variational data assimilation, (iii) correlation between ozone and potential vorticity (PV) as an indicator of airmasses and (iv) anisotropic and inhomogeneous horizontal background error correlations in the Ex-UTLS, spreading information towards unobserved regions along PV isopleths. This setup demonstrated substantial improvements to basic approaches in exploring new data on the spatial extend and alignment of airmasses down to small-scale filaments in the Ex-UTLS. Tomographic observations provide detailed insight for reconstructing filamentary foldings along airmass boundaries above the tropopause during this case study.

Citation: Vogel, A., Ungermann, J., and Elbern, H.: Analyzing trace gas filaments in the Ex-UTLS by 4D-variational assimilation of airborne tomographic retrievals, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-308, in review, 2017.
Annika Vogel et al.
Annika Vogel et al.
Annika Vogel et al.

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Short summary
The potential for chemical state analysis at tropopause heights was investigated by combining airborne tomographic observations with a chemical data-assimilation system in form of a case study. Related developments include the use of potential vorticity for ozone initialization and flow-dependent horizontal correlations. This setup demonstrated substantial improvements in terms of spatial extend and alignment of atmospheric structures down to filamentary foldings along airmass boundaries.
The potential for chemical state analysis at tropopause heights was investigated by combining...
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