Improving retrieval quality for airborne limb sounders by horizontal regularisation

Ungermann, Jörn

doi:10.5194/amt-6-15-2013

Cited by 17 publications

(20 citation statements)

References 37 publications

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“…This problem can be efficiently solved by quasi Newtontype methods, in our case a truncated conjugate gradientbased trust-region scheme (Ungermann, 2013).…”

Section: Level 2 Processingmentioning

confidence: 99%

Level 2 processing for the imaging Fourier transform spectrometer GLORIA: derivation and validation of temperature and trace gas volume mixing ratios from calibrated dynamics mode spectra

Ungermann¹,

Blank²,

Dick³

et al. 2015

Atmos. Meas. Tech.

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Abstract. The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb imager combining a two-dimensional infrared detector with a Fourier transform spectrometer. It was operated aboard the new German Gulfstream G550 High Altitude LOng Range (HALO) research aircraft during the Transport And Composition in the upper Troposphere/lowermost Stratosphere (TACTS) and Earth System Model Validation (ESMVAL) campaigns in summer 2012. This paper describes the retrieval of temperature and trace gas (H 2 O, O 3 , HNO 3 ) volume mixing ratios from GLORIA dynamics mode spectra that are spectrally sampled every 0.625 cm −1 . A total of 26 integrated spectral windows are employed in a joint fit to retrieve seven targets using consecutively a fast and an accurate tabulated radiative transfer model. Typical diagnostic quantities are provided including effects of uncertainties in the calibration and horizontal resolution along the line of sight. Simultaneous in situ observations by the Basic Halo Measurement and Sensor System (BAHAMAS), the Fast In-situ Stratospheric Hygrometer (FISH), an ozone detector named Fairo, and the Atmospheric chemical Ionization Mass Spectrometer (AIMS) allow a validation of retrieved values for three flights in the upper troposphere/lowermost stratosphere region spanning polar and sub-tropical latitudes. A high correlation is achieved between the remote sensing and the in situ trace gas data, and discrepancies can to a large extent be attributed to differences in the probed air masses caused by different sampling characteristics of the instruments.This 1-D processing of GLORIA dynamics mode spectra provides the basis for future tomographic inversions from circular and linear flight paths to better understand selected dynamical processes of the upper troposphere and lowermost stratosphere.

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“…This problem can be efficiently solved by quasi Newtontype methods, in our case a truncated conjugate gradientbased trust-region scheme (Ungermann, 2013).…”

Section: Level 2 Processingmentioning

confidence: 99%

Level 2 processing for the imaging Fourier transform spectrometer GLORIA: derivation and validation of temperature and trace gas volume mixing ratios from calibrated dynamics mode spectra

Ungermann¹,

Blank²,

Dick³

et al. 2015

Atmos. Meas. Tech.

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“…Ungermann et al (2012) improved this setup by employing a more accurate line-of-sight determination and a finer retrieval grid. In addition, horizontal regularisation was added to lower the impact of stochastic error sources on the results (see Ungermann, 2013).…”

Section: Appendix a Retrievalmentioning

confidence: 99%

Filamentary structure in chemical tracer distributions near the subtropical jet following a wave breaking event

et al. 2013

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Abstract. This paper presents a set of observations and analyses of trace gas cross sections in the extratropical upper troposphere/lower stratosphere (UTLS). The spatially highly resolved (≈0.5 km vertically and 12.5 km horizontally) cross sections of ozone (O 3 ), nitric acid (HNO 3 ), and peroxyacetyl nitrate (PAN), retrieved from the measurements of the CRISTA-NF infrared limb sounder flown on the Russian M55-Geophysica, revealed intricate layer structures in the region of the subtropical tropopause break. The chemical structure in this region shows an intertwined stratosphere and troposphere. The observed filaments in all discussed trace gases are of a spatial scale of less than 0.8 km vertically and about 200 km horizontally across the jet stream. Backward trajectory calculations confirm that the observed filaments are the result of a breaking Rossby wave in the preceding days. An analysis of the trace gas relationships between PAN and O 3 identifies four distinct groups of air mass: polluted subtropical tropospheric air, clean tropical upper-tropospheric air, the lowermost stratospheric air, and air from the deep stratosphere. The tracer relationships further allow the identification of tropospheric, stratospheric, and the transitional air mass made of a mixture of UT and LS air. Mapping of these air mass types onto the geo-spatial location in the cross sections reveals a highly structured extratropical transition layer (ExTL). Finally, the ratio between the measured reactive nitrogen species (HNO 3 + PAN + ClONO 2 ) and O 3 is analysed to estimate the influence of tropospheric pollution on the extratropical UTLS.In combination, these diagnostics provide the first example of a multi-species two-dimensional picture of the inhomogeneous distribution of chemical species within the UTLS region. Since Rossby wave breaking occurs frequently in the region of the tropopause break, these observed fine-scale filaments are likely ubiquitous in the region. The implications of the layered structure for chemistry and radiation need to be examined, and the representation of this structure in chemistry-climate models is discussed.

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“…The retrieval technique and validation against measurements by other instruments is described in detail by Weigel et al (2010) and Ungermann et al (2012). The derivation of the trace gas cross-sections was since improved by means of cross-section retrievals to further reduce the effect of stochastic errors such as a remaining line-ofsight uncertainty (Ungermann, 2013).…”

Section: Crista-nf Observationsmentioning

confidence: 99%

Observations of filamentary structures near the vortex edge in the Arctic winter lower stratosphere

Kalicinsky

Grooß²,

Günther³

et al. 2013

Atmos. Chem. Phys.

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Abstract. The CRISTA-NF (Cryogenic Infrared Spectrometers and Telescope for the Atmosphere -New Frontiers) instrument is an airborne infrared limb sounder operated aboard the Russian research aircraft M55-Geophysica. The instrument successfully participated in a large Arctic aircraft campaign within the RECONCILE (Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions) project in Kiruna (Sweden) from January to March 2010. This paper concentrates on the measurements taken during one flight of the campaign, which took place on 2 March in the vicinity of the polar vortex. We present two-dimensional cross-sections of derived volume mixing ratios for the trace gases CFC-11, O 3 , and ClONO 2 with an unprecedented vertical resolution of about 500 to 600 m for a large part of the observed altitude range (≈ 6-19 km) and a dense horizontal sampling along flight direction of ≈ 15 km. The trace gas distributions show several structures, for example a part of the polar vortex and a vortex filament, which can be identified by means of O 3 -CFC-11 tracer-tracer correlations.The observations made during this flight are interpreted using the chemistry and transport model CLaMS (Chemical Lagrangian Model of the Stratosphere). Comparisons of the observations with the model results are used to assess the performance of the model with respect to advection, mixing, and the chemistry in the polar vortex. These comparisons confirm the capability of CLaMS to reproduce even very small-scale structures in the atmosphere, which partly have a vertical extent of only 1 km. Based on the good agreement between simulation and observation, we use artificial (passive) tracers, which represent different air mass origins (e.g. vortex, tropics), to further analyse the CRISTA-NF observations in terms of the composition of air mass origins. These passive tracers clearly illustrate the observation of filamentary structures that include tropical air masses. A characteristic of the Arctic winter 2009/10 was a sudden stratospheric warming in December that led to a split of the polar vortex. The vortex re-established at the end of December. Our passive tracer simulations suggest that large parts of the re-established vortex consisted to about 45 % of high-and mid-latitude air.

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Improving retrieval quality for airborne limb sounders by horizontal regularisation

Cited by 17 publications

References 37 publications

Level 2 processing for the imaging Fourier transform spectrometer GLORIA: derivation and validation of temperature and trace gas volume mixing ratios from calibrated dynamics mode spectra

Level 2 processing for the imaging Fourier transform spectrometer GLORIA: derivation and validation of temperature and trace gas volume mixing ratios from calibrated dynamics mode spectra

Filamentary structure in chemical tracer distributions near the subtropical jet following a wave breaking event

Observations of filamentary structures near the vortex edge in the Arctic winter lower stratosphere

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