T. von Clarmann

Selection of optimized microwindows for atmospheric spectroscopy.

In atmospheric Fourier transform spectroscopy so-called microwindows are usually analyzed for retrieval of trace constituents rather than the spectrum as a whole. These microwindows, which are sets of consecutive spectral grid points, contain one or more prominent transitions of the target species, whereas it is desirable for the signal of interfering species to be minimum. An objective, quantitative method is presented to optimize the microwindow boundaries with respect to random errors, signal of interfering species, other parameter and systematic errors and to select optimum microwindows with respect to their associated retrieval errors. Case studies for N(2)O microwindows are performed for a spaceborne limb emission experiment to assess the dependence of the optimum microwindow width on the retrieval concept.

Mixing Processes during the Antarctic Vortex Split in September–October 2002 as Inferred from Source Gas and Ozone Distributions from ENVISAT–MIPAS

Abstract In late September 2002, an Antarctic major stratospheric warming occurred, which led to a strong distortion of the southern polar vortex and to a split of its mid- and upper-stratospheric parts. Such an event had never before been observed since the beginning of regular Antarctic stratospheric temperature observations in the 1950s. The split is studied by means of nonoperational level-2 CH4, N2O, CFC-11, and O3 data, retrieved at the Institute for Meteorology and Climate Research Karlsruhe (IMK) from high-resolution atmospheric limb emission spectra from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the European research satellite, Environmental Satellite (ENVISAT). Retrieved horizontal and vertical distributions of CH4 and N2O show good consistency with potential vorticity fields of the European Centre for Medium-Range Weather Forecasts (ECMWF) analysis for the entire period under investigation, even for fine structures such as vortex filaments. Tracer correlatio...

Retrieval of stratospheric O3, HNO3 and ClONO2 profiles from 1992 MIPAS-B limb emission spectra: Method, results, and error analysis

Within the framework of the European Arctic Stratospheric Ozone Experiment, two flights of the balloon-borne MIPAS-B limb emission spectrometer were performed in the Arctic stratosphere from Kiruna, northern Sweden. During the early hours of January 13 and the night from March 14 to March 15, 1992, several limb sequences of infrared spectra were recorded which have permitted the retrieval of vertical profiles of many trace gases relevant for ozone chemistry. In the present work, the retrieval strategy, error estimation strategy, and resulting profiles of O3, HNO3, and ClONO2 are reported. The data analysis procedure, consisting of data preprocessing including calibration, analysis of auxiliary data including temperature profiles and line of sight determination, and retrieval of trace gas profiles, is described in detail. The last is carried out by means of multiparameter nonlinear least squares fitting in combination with onion peeling. An astonishingly high ClONO2 amount of 2.6 ppb by volume at about 19-km altitude was inferred for the March flight. A rigorous error analysis, which takes into account systematic and random errors and their often nonlinear impact on the results, proves the significance of the retrieved trace gas profiles.

Spectroscopic evidence for NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds

Spectroscopic evidence for β-NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds M. Höpfner, B. P. Luo, P. Massoli, F. Cairo, R. Spang, M. Snels, G. Di Donfrancesco, G. Stiller, T. von Clarmann, H. Fischer, and U. Biermann Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung, Karlsruhe, Germany Institut für Atmosphäre und Klima, ETH-Hönggerberg, Zürich, Switzerland Consiglio Nazionale delle Ricerche, Istituto di Scienze dell’Atmosfera e del Clima, Rome, Italy Forschungszentrum Jülich, Institut für Chemie und Dynamik der Geosphäre, Jülich, Germany Ente per le Nuove tecnologie, l’Energie e l’Ambiente, Rome, Italy Max-Planck-Institut für Chemie, Abteilung Atmosphärenchemie, Mainz, Germany now at: Referat für Umweltund Energiepolitik des SPD-Parteivorstandes, Berlin, Germany

A blind test retrieval experiment for infrared limb emission spectrometry

The functionality and characteristics of six different data processors (i.e., retrieval codes in their actual software and hardware environment) for analysis of high-resolution limb emission infrar ...

An enhanced HNO3 second maximum in the Antarctic midwinter upper stratosphere 2003

Vertical profiles of stratospheric HNO 3 were retrieved from limb emission spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the Envisat research satellite during the Antarctic winter 2003. A high second maximum of HNO 3 was found around 34 km altitude with abundances up to 14 ppbv HNO 3 during July. Similar high abundances have not been reported in the literature for previous winters, but for the subsequent Arctic winter 2003/2004, after severe perturbations due to solar proton events. The second HNO 3 maximum in the Antarctic stratosphere started to develop in early June 2003, reached peak values during July 2003, and decreased to about 7 ppbv at the end of August while being continuously transported downward before finally forming a single HNO 3 layer over all latitudes in the lower stratosphere together with the out-of-vortex primary HNO 3 maximum. The HNO 3 decrease in August 2003 was correlated with photochemical buildup of other NO v species as ClONO 2 and NO x . From the time scales observed, it can be ruled out that the 2003 long-term HNO 3 enhancements were caused by local gas phase reactions immediately after the solar proton event on 29 May 2003. Instead, HNO 3 was produced by ion cluster chemistry reactions and/or heterogeneous reactions on sulfate aerosols via N 2 O 5 from high amounts of NOy being continuously transported downward from the lower thermosphere during May to August.

Mesospheric and stratospheric NOy produced by energetic particle precipitation during 2002–2012

Global distributions of the six principal reactive nitrogen (NOy) compounds (HNO3, NO2, NO, N2O5, ClONO2, and HNO4) have been derived from midinfrared limb emission spectra taken by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board Envisat during 2002–2012. The obtained data set provides a unique climatological record of NOy in the middle atmosphere. The contribution of NOy produced by energetic particle precipitation (EPP) has been discriminated from that produced by N2O oxidation using a tracer correlation method based on MIPAS CH4 and CO observations. The EPP-NOy distributions, obtained in the vertical range 20–70km, allow to trace odd nitrogen polar winter descent from the mesosphere down to the middle and lower stratosphere, where it contributes to catalytic ozone destruction. Highest EPP-NOy concentrations (up to 1 ppmv) are found in the winter solstice mesosphere, decreasing continuously with time and toward lower altitudes. Springtime peak concentrations of a few parts per billion by volume are observed at 22–25km, demonstrating a regular EPP impact on the entire stratosphere. The interannual variation shows a clear solar cycle signal in consonance with geomagnetic activity variations. A pronounced hemispheric asymmetry of EPP-NOy is observed, with higher concentrations in the Southern Hemisphere (SH) and stronger variability in the Northern Hemisphere (NH). Poleward of 60°, EPP-NOy contributes to the winter NOy column at 20–70km by 10–40% in the SH and 1–30% in the NH. Smaller contributions (0.1–1%) are found at midlatitudes (30°–60°). This study provides the first assessment of EPP-NOy intrusions into the stratosphere based on globally available satellite data on a decadal scale.

NOy partitioning and budget and its correlation with N2O in the Arctic vortex and in summer midlatitudes in 1997

Vertical profiles of the most important species of nocturnal total reactive nitrogen (NO y = NO 2 + HNO 3 + CIONO 2 + 2 N 2 O 5 + HO 2 NO 2 ) together with its source gas N 2 O were retrieved from infrared limb emission spectra measured by the Michelson Interferometer for Passive Atmospheric Sounding, Balloon-borne version (MIPAS-B) instrument inside the late winter arctic vortex from Kiruna (Sweden, 68°N) on 24 March 1997 and in summer midlatitudes from Gap (France, 44°N) on 2 July 1997. The measured data were compared to calculations performed with the three-dimensional chemistry transport model (CTM) Karlsruhe Simulation model of the Middle Atmosphere (KASIMA). The results show that in the late winter arctic vortex most of the available nitrogen and chlorine is in the form of HNO 3 and CIONO 2 , respectively. An anomalous N 2 O-NO y correlation observed in March 1997 appears to be caused to a large extent by quasi-horizontal mixing of air masses across the vortex edge. However, near 20 km some denitrification of ∼1.5 to 2 ppbv NO y could be observed. The N 2 O profile measured in July 1997 indicates remnants of polar vortex air and is not reproduced by the CTM at the same location. However, the profile shapes of the individual compounds of the NO y family as well as the NO x /NO y ratio are reproduced fairly well by the model.

Optical and microphysical parameters of the Mt. Pinatubo aerosol as determined from MIPAS-B mid-IR limb emission spectra

High-resolution mid-IR limb emission spectra were recorded during a flight of the Michelson interferometer for passive atmospheric sounding, balloon-borne version (MIPAS-B) from Kiruna, northern Sweden (68°N) on March 14/15, 1992. These spectra are affected by the Mt. Pinatubo stratospheric aerosol, which caused an enhanced continuum emission, especially in spectra of low tangent altitudes. Aerosol extinction coefficients were retrieved from MIPAS-B spectra at approximately 60 spectral positions in the 750–980 cm−1 and 1180–1380 cm−1 spectral ranges. Retrieved aerosol extinction coefficients range from 6×10−4 km−1 to 3×10−3 km−1 in tangent altitudes 11.3 km and 14.5 km and from 5×10−5 km−1 to 1×10−3 km−1 in 16.1 km. Their distinct spectral shape indicates the presence of H2SO4-H2O droplets. Compositions and size distribution parameters were retrieved by least squares fitting of Mie-generated spectral extinction coefficients to the ones derived from the spectra. Estimated spectral single-scattering albedos between 0.08 and 0.3 indicate the significance of thermal multiple scattering. Multiple-scattering corrections led to an increase of spectral extinction coefficients by 5–50% with highest changes at lowest tangent altitudes. Accordingly, estimated volume densities have increased by 4–20% to values of 3.66, 2.85, and 0.93 μm3 cm−3 for tangent altitudes 11.3, 14.5, and 16.1 km, respectively. Retrieved H2SO4 weights of 66–70% are in good agreement with values derived from stratospheric temperatures and water vapor partial pressures. Estimated surface densities are systematically low in comparison with in situ size distribution measurements. This finding is explained by the underestimation of small particles by the use of a monomodal size distribution in the analysis. Retrieved effective radii of up to 0.8 μm were found to be consistent with the temporal evolution of the Mt. Pinatubo aerosol.

SPARC Data Initiative: A comparison of ozone climatologies from international satellite limb sounders

A comprehensive quality assessment of the ozone products from 18 limb-viewing satellite instruments is provided by means of a detailed intercomparison. The ozone climatologies in form of monthly zonal mean time series covering the upper troposphere to lower mesosphere are obtained from LIMS, SAGE I/II/III, UARS-MLS, HALOE, POAM II/III, SMR, OSIRIS, MIPAS, GOMOS, SCIAMACHY, ACE-FTS, ACE-MAESTRO, Aura-MLS, HIRDLS, and SMILES within 1978–2010. The intercomparisons focus on mean biases of annual zonal mean fields, interannual variability, and seasonal cycles. Additionally, the physical consistency of the data is tested through diagnostics of the quasi-biennial oscillation and Antarctic ozone hole. The comprehensive evaluations reveal that the uncertainty in our knowledge of the atmospheric ozone mean state is smallest in the tropical and midlatitude middle stratosphere with a 1σ multi-instrument spread of less than ±5%. While the overall agreement among the climatological data sets is very good for large parts of the stratosphere, individual discrepancies have been identified, including unrealistic month-to-month fluctuations, large biases in particular atmospheric regions, or inconsistencies in the seasonal cycle. Notable differences between the data sets exist in the tropical lower stratosphere (with a spread of ±30%) and at high latitudes (±15%). In particular, large relative differences are identified in the Antarctic during the time of the ozone hole, with a spread between the monthly zonal mean fields of ±50%. The evaluations provide guidance on what data sets are the most reliable for applications such as studies of ozone variability, model-measurement comparisons, detection of long-term trends, and data-merging activities.