The chemical composition of RF discharges in methane

In dieser Arbeit wurde die chemische Zusammensetzung reaktiver Radiofrequenz- Plasmen (13.56 MHZ) mit Methan als Quellegas untersucht mittels Infrarot- Absorptionsspektroskopie mit Diodenlasern. Der experimentelle Schwerpunkt lag in der Bestimmung der Dichten von fünf für die Plasmachemie besonders wichtigen Molekülen als Funktionen von den externen Parametern (wie Leistung, Durchfluss und Kopplungsmechanismus). Zusätzlich wurde ein System aus stark vereinfachten Ratengleichungen aufgestellt. Durch Fitten der gemessenen Dichten in Abhängigkeit von der eingekoppelten Leistung oder während der Ein- und Ausschaltvorgänge konnten Informationen über die Ratenkoeffizienten gewonnen werden. Außerdem konnte die Elektronentemperatur unter der Annahme einer Elektronenenergieverteilungsfunktion (Maxwell oder Druyvesteyn) abgeschätzt werden

BROADBAND OZONE ABSORPTION CROSS SECTIONS IN NEAR UV - NEAR IR

Author Institution: Institute of Environmental Physics, University of Bremen, GermanyThe global monitoring of the ozone concentration using both satellite borne and ground based instruments plays a key role in the determination of the long-term trends for the stratospheric ozone layer and air quality related studies. The requirement to measure small changes in stratospheric and tropospheric ozone places strong demands on the accuracy of the ozone absorption cross-sections used in retrievals of the spectra delivered by remote sensing spectrometers. We report on the new dataset, which uniquely combines spectral resolution as high as 0.02 nm with a broad spectral coverage from 220 nm to 1100 nm for convenient use in various current and future projects. The new dataset enables the accurate convolution with the slit functions of all currently relevant ground based and satellite based remote sensing instruments. The absolute accuracy of about three percent or better for most of the spectral range, and wavelength accuracy better than 0.005 nm, has been achieved at eleven temperatures from 195 to 293K. New dataset includes regions poorly covered so far. In overlapping regions comparison of the new ozone cross-sections with the previously available datasets shows good agreement within the uncertainty limits. We provide analysis of the consistency of our dataset and report on the impact of the new data on the ozone retrievals based on tests performed by different groups. We believe that the new cross-sections have inherited and combined the advantages over the previous datasets to the maximum possible extent. New dataset is available for scientific community. We hope that groups working on the ozone observations will find new dataset useful on a long-term basis

Impact of ozone cross-section choice on WFDOAS total ozone retrieval applied to GOME, SCIAMACHY, and GOME-2 (1995-present)

Technical Note Issue 2 (January 2011) with updates from November 2013. A contribution to ACSO http://igaco-o3.fmi.fi/ACSO/. In this technical note we investigate how the choice of ozone cross-sections impact the WFDOAS (Weighting Function Differential Optical Absorption Spectroscopy) total ozone retrieval (Coldewey-Egbers et al., 2005) for the satellite instruments GOME, GOME-2, and SCIAMACHY

NEW HIGH RESOLUTION OZONE ABSORPTION CROSS SECTIONS

Author Institution: Institute for Environmental Physics, University of Bremen, Otto-Hahn Allee 1, D-28359 Bremen, GermanyWe report on the work devoted to the up-to-date measurements of the ozone absorption cross-sections. The main goal of the project is to produce a consolidated and consistent set of high resolution cross-sections for different temperatures. The work is inspired by the more than two decades (1995 - 2020) of the global ozone observations, which are planned to be carried out using current and future atmospheric chemistry instruments (GOME, GOME-2, SCIAMACHY, SAGE II, etc). New laboratory measurements provide ozone cross-section in the spectral range 230 1000 nm at a spectral resolution of 0.02 nm with absolute intensity accuracy of at least 2 percents, and wavelength accuracy better than 0.001 nm in the temperature range 193-293 K in 10 K steps. A lot of attention is paid to the accuracy of determining the temperature of the ozone flow and absolute calibration of relative spectra. We provide analysis and comparison of the previously available ozone cross-sections databases versus our new dataset and report on the impact of the new data on the ozone retrievals. New cross-sections dataset will improve significantly the ozone data quality and time series as required for climate, air quality, and stratospheric ozone trend studies. Updated ozone cross-sections will be available for reprocessing with satellite spectrometers and to the scientific community as well. Release of the new dataset is planned for the summer 2011

TEMPERATURE DEPENDENT OZONE ABSORPTION CROSS SECTIONS FOR SATTELITE SPECTROMETERS: NEW LABORATORY MEASUREMENTS

Author Institution: Institute For Environmental Physics, University of Bremen, Otto-Hahn Allee 1, D-28359 Bremen, GermanyWe report on the work devoted to the up-to-date measurements of the ozone absorption cross-sections. The main goal of the project is to produce a consolidated and consistent set of high resolution cross-sections for satellite spectrometers series that allows a derivation of the harmonized long term data set. It is expected that five atmospheric chemistry instruments will provide two or more decades (1995 - 2020) of ozone observations. Information from different sensors has to be combined for a consistent long-term data record, since the lifetime of individual satellite missions is limited. The harmonization of cross-sections is strongly supported by new experimental work. New laboratory measurements of ozone cross-section are underway that will improve a) absolute scaling of cross-sections, b) temperature dependence of cross-sections and c) wavelength calibration. We take advantage of a Fourier transform spectrometer and Echelle spectrophotometer to extend the dynamic range of the system (covering several orders of magnitude in cross-sections from UV up to the near IR). Measurements cover the spectral range 220 - 1000 nm at a spectral resolution of 0.02 nm in UV/VIS with absolute intensity accuracy of at least 2 percents, and wavelength accuracy better than 0.001 nm in the temperature range 193-293 K in 10 K steps. A lot of attention is paid to the accuracy of determining the temperature of the ozone flow and new methods for absolute calibration of relative spectra. New cross-sections dataset will improve significantly the ozone data quality and time series as required for climate, air quality, and stratospheric ozone trend studies. Updated ozone cross-sections will be available for reprocessing with satellite spectrometers and to the scientific community as well

LINE BROADENING PARAMETERS OF METHANE AT 6000 CM−1^{-1}

Author Institution: Insitute of Environmental Physics, University of Bremen, Germany; Earth Observation Science Group, University of Leicester, UKBeing one of the most important greenhouse gases, methane (CH$_4$) is also modified by anthropogenic activity. Nowadays, it can be monitored globally from space on the long-term scale using combinations of different remote sensing instruments. The critical point for the retrieval algorithms is the knowledge of the spectroscopic parameters. Although a significant amount of spectroscopic data on CH$_4$ is available, the information on the line parameters in mid infrared (MIR) spectral region is inadequate for accurate remote sensing applications and there is a need for improved spectroscopic line parameters. We report on the improved spectroscopic line parameters for CH$_4$ in the spectral regions used by SCIAMACHY and TANSO instruments around 6000 cm$^{-1}$. New data were obtained using high resolution absorption spectra of CH$_4$, perturbed by oxygen, nitrogen and air. Spectra were measured using Fourier transform spectrometer in a broad range of total pressures from 2 to 1000 mbar and temperatures down to 196 K. Calculations of broadening parameters were performed using Reference Forward Model assuming Voigt line profile within international collaboration between the Molecular Spectroscopy Laboratory in IUP Bremen, and Earth Observation Science Group, University of Leicester, UK. Accuracy of the new data matches the level of the demands of modern datasets and remote sensing. The new data were compared with the data included in the latest HITRAN edition and other published works. Before release for the general scientific community, the new data was tested on the TANSO and SCIAMACHY retrievals

Absorption cross-sections of Ozone in the ultraviolet and visible spectral regions – Status report 2015

International audienceThe activity “Absorption Cross-Sections of Ozone” (ACSO) started in 2008 as a joint initiative of the International Ozone Commission (IO3C), the World Meteorological Organization (WMO) and the IGACO (“Integrated Global Atmospheric Chemistry Observations”) O3/UV subgroup to study, evaluate, and recommend the most suitable ozone absorption cross-section laboratory data to be used in atmospheric ozone measurements. The evaluation was basically restricted to ozone absorption cross-sections in the UV range with particular focus on the Huggins band. Up until now, the data of Bass and Paur published in 1985 (BP, 1985) are still officially recommended for such measurements. During the last decade it became obvious that BP (1985) cross-section data have deficits for use in advanced space-borne ozone measurements. At the same time, it was recognized that the origin of systematic differences in ground-based measurements of ozone required further investigation, in particular whether the BP (1985) cross-section data might contribute to these differences.In ACSO, different sets of laboratory ozone absorption cross-section data (including their dependence on temperature) of the group of Reims (France) and , 1992, 1995, abbreviated as BDM, 1995) and those of [8], and [7], (abbreviated as SER, 2014) were examined for use in atmospheric ozone measurements in the Huggins band.In conclusion, ACSO recommends:- The spectroscopic data of BP (1985) should no longer be used for retrieval of atmospheric ozone measurements.- For retrieval of ground-based instruments of total ozone and ozone profile measurements by the Umkehr method performed by Brewer and Dobson instruments data of SER (2014) are recommended to be used. When SER (2014) is used, the difference between total ozone measurements of Brewer and Dobson instruments are very small and the difference between Dobson measurements at AD and CD wavelength pairs are diminished.- For ground-based Light Detection and Ranging (LIDAR) measurements the use of BDM (1995) or SER (2014) is recommended.- For satellite retrieval the presently widely used data of BDM (1995) should be used because SER (2014) seems less suitable for retrievals that use wavelengths close to 300 nm due to a deficiency in the signal-to-noise ratio in the SER (2014) dataset