A. Richter

Universität Bremen, Bremen, Bremen, Germany

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Publications (549)913.76 Total impact

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    ABSTRACT: The Airborne imaging differential optical absorption spectroscopy (DOAS) instrument for Measurements of Atmospheric Pollution (AirMAP) has been developed for the purpose of trace gas measurements and pollution mapping. The instrument has been characterized and successfully operated from aircraft. Nitrogen dioxide (NO2) columns were retrieved from the AirMAP observations. A major benefit of the push-broom imaging instrument is the spatially continuous, gap-free measurement sequence independent of flight altitude, a valuable characteristic for mapping purposes. This is made possible by the use of a charge coupled device (CCD) frame-transfer detector. A broad field of view across track of around 48° is achieved with wide-angle entrance optics. This leads to a swath width of about the same size as the flight altitude. The use of fibre coupled light intake optics with sorted light fibres allows flexible instrument positioning within the aircraft and retains the very good imaging capabilities. The measurements yield ground spatial resolutions below 100 m depending on flight altitude. The number of viewing directions is chosen from a maximum of 35 individual viewing directions (lines of sight, LOS) represented by 35 individual fibres. The selection is adapted to each situation by averaging according to signal-to-noise or spatial resolution requirements. Observations at 30 m spatial resolution are obtained when flying at 1000 m altitude and making use of all 35 viewing directions. This makes the instrument a suitable tool for mapping trace gas point sources and small-scale variability. The position and aircraft attitude are taken into account for accurate spatial mapping using the Attitude and Heading Reference System of the aircraft. A first demonstration mission using AirMAP was undertaken in June 2011. AirMAP was operated on the AWI Polar-5 aircraft in the framework of the AIRMETH-2011 campaign. During a flight above a medium-sized coal-fired power plant in north-west Germany, AirMAP clearly detected the emission plume downwind from the exhaust stack, with NO2 vertical columns around 2 × 1016 molecules cmg'2 in the plume centre. NO x emissions estimated from the AirMAP observations are consistent with reports in the European Pollutant Release and Transfer Register. Strong spatial gradients and variability in NO2 amounts across and along flight direction are observed, and small-scale enhancements of NO2 above a motorway are detected.
    No preview · Article · Dec 2015 · Atmospheric Measurement Techniques
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    ABSTRACT: In this study, mixing ratios of NO2 (XNO2) and HCHO (XHCHO) in the free troposphere are derived from two Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) data sets collected at Zugspitze (2650 m a.s.l., Germany) and Pico Espejo (4765 m a.s.l., Venezuela). The estimation of NO2 and HCHO mixing ratios is based on the modified geometrical approach, which assumes a single-scattering geometry and a scattering point altitude close to the instrument. Firstly, the horizontal optical path length (hOPL) is obtained from O4 differential slant column densities (DSCDs) in the horizontal (0°) and vertical (90°) viewing directions. Secondly, XNO2 and XHCHO are estimated from the NO2 and HCHO DSCDs at the 0 and 90° viewing directions and averaged along the obtained hOPLs. As the MAX-DOAS instrument was performing measurements in the ultraviolet region, wavelength ranges of 346–372 and 338–357 nm are selected for the DOAS analysis to retrieve NO2 and HCHO DSCDs, respectively. In order to compare the measured O4 DSCDs and moreover to perform some sensitivity tests, the radiative transfer model SCIATRAN with adapted altitude settings for mountainous terrain is operated to simulate synthetic spectra, on which the DOAS analysis is also applied. The overall agreement between measured and synthetic O4 DSCDs is better for the higher Pico Espejo station than for Zugspitze. Further sensitivity analysis shows that a change in surface albedo (from 0.05 to 0.7) can influence the O4 DSCDs, with a larger absolute difference observed for the horizontal viewing direction. Consequently, the hOPL can vary by about 5 % throughout the season, for example when winter snow cover fully disappears in summer. Typical values of hOPLs during clear sky conditions are 19 km (14 km) at Zugspitze and 34 km (26.5 km) at Pico Espejo when using the 346–372 nm (338–357 nm) fitting window. The estimated monthly values of XNO2 (XHCHO), averaged over these hOPLs during clear sky conditions, are in the range of 60–100 ppt (500–950 ppt) at Zugspitze and 8.5–15.5 ppt (255–385 ppt) at Pico Espejo. Interestingly, multi-year averaged monthly means of XNO2 and XHCHO increase towards the end of the dry season at the Pico Espejo site, suggesting that both trace gases are frequently lifted above the boundary layer as a result of South American biomass burning.
    No preview · Article · Nov 2015 · Atmospheric Chemistry and Physics
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    ABSTRACT: Intense, cyclone-like shaped plumes of tropospheric bromine monoxide (BrO) are regularly observed by GOME-2 on board the MetOp-A satellite over Arctic sea ice in polar spring. These plumes are often transported by high latitude cyclones, sometimes over several days despite the short atmospheric lifetime of BrO. However, only few studies have focused on the role of polar weather systems in the development, duration and transport of tropospheric BrO plumes during bromine explosion events. The latter are caused by an autocatalytic chemical chain reaction associated with tropospheric ozone depletion and initiated by the release of bromine from cold brine covered ice or snow to the atmosphere. In this manuscript, a case study investigating a comma-shaped BrO plume which developed over the Beaufort Sea and was observed by GOME-2 for several days is presented. By making combined use of satellite data and numerical models, it is shown that the occurrence of the plume was closely linked to frontal lifting in a polar cyclone and that it most likely resided in the lowest 3 km of the troposphere. In contrast to previous case studies, we demonstrate that the dry conveyor belt, a potentially bromine-rich stratospheric air stream which can complicate interpretation of satellite retrieved tropospheric BrO, is spatially separated from the observed BrO plume. It is concluded that weather conditions associated with the polar cyclone favored the bromine activation cycle and blowing snow production, which may have acted as a bromine source during the bromine explosion event.
    No preview · Article · Sep 2015 · Atmospheric Chemistry and Physics
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    T. Wagner · H. Harder · J. Joiner · P. Laj · A. Richter
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    ABSTRACT: The AMT executive editors received a complaint that the method presented in the paper by Mak et al. (2013) was largely based on an earlier invention by Pieter Tans (see e.g., the paper by Karion et al., 2010), but this earlier invention was not mentioned or referenced in the paper by Mak et al. (2013). For the AMT executive editors it is not possible to make a clear decision in this conflict. Unfortunately, it was also not possible to reach a consensus between the involved parties. This editorial note thus has two aims: 1. to make the readers of the paper by Mak et al. (2013) aware of this conflict;
    Preview · Article · Aug 2015 · Atmospheric Measurement Techniques
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    ABSTRACT: In order to promote the development of the passive DOAS technique the Multi Axis DOAS – Comparison campaign for Aerosols and Trace gases (MAD-CAT) was held at the Max Planck Institute for Chemistry in Mainz, Germany from June to October 2013. During this campaign we present intercomparison results for tropospheric slant column densities (SCDs) of nitrous acid (HONO) retrieved by seven research groups using same baseline DOAS fit parameters. In the intercomparison, the standard deviation (SD) and mean deviation of HONO dSCD for all participants from the reference are quite small, mostly less than ± 0.4 × 1015 molec/cm2 close to the fit error. And for the days with high HONO concentration, the correlation coefficients and slopes of linear regression are close to unity with quite small intercept for low elevation angles (EA). In general good agreement of the HONO dSCD data sets was found. All the participants also analyse the synthetic spectra generated by SCIATRAN model using the baseline fit settings to evaluate the systematic errors of HONO dSCD from their respective fit programs. Furthermore, the optimal estimation algorithms are applied to the Hefei and BIRA HONO dSCDs to retrieve the profiles of HONO volume mixing ratios and compared with simulations from chemical model on some days with relative high HONO concentration.
    Full-text · Conference Paper · Jul 2015
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    ABSTRACT: The MACC III (Modelling Atmospheric Composition and Climate, www.copernicus‐atmosphere.eu) project is establishing the core global and regional atmospheric environmental service delivered as a component of the European Earth observation programme Copernicus. The global MACC near-­‐real time (NRT) service provides daily analyses and forecasts of trace gas and aerosol concentrations. This document contains verification results for the upgrade of the NRT service planned for July 2015. The new model configuration (the e-suite) is operated in parallel to the operational NRT service (the o-­‐suite) for several months. For more details about the validation approaches and references we refer to the NRT validation reports of MACC-­‐II. Below the main results are summarised from a comparison of the performance of the new e-suite run (g9rr, period October 2014 -­‐ May 2015), the operational run (o‐suite) and independent bservations.
    Full-text · Technical Report · Jun 2015

  • No preview · Article · Jun 2015
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    ABSTRACT: The MACC III (Monitoring Atmospheric Composition and Climate III, http://www.copernicus-­atmosphere.eu) project is establishing the core global and regional atmospheric environmental service delivered as a component of the European Earth observation programme Copernicus. The MACC global near-real time (NRT) service provides daily analyses and forecasts of trace gas and aerosol concentrations. This document presents the validation statistics and system evolution of the MACC NRT service for the period until 1 March 2015. This document is updated every 3 months.
    Full-text · Technical Report · May 2015
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    ABSTRACT: Daily global analyses and 5-day forecasts are generated in the context of the European Monitoring Atmospheric Composition and Climate (MACC) project using an extended version of the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). The IFS now includes modules for chemistry, deposition and emission of reactive gases, aerosols, and greenhouse gases, and the 4-dimensional variational data assimilation scheme makes use of multiple satellite observations of atmospheric composition in addition to meteorological observations. This paper describes the data assimilation setup of the new Composition-IFS (C-IFS) with respect to reactive gases and validates analysis fields of ozone (O3), carbon monoxide (CO), and nitrogen dioxide (NO2) for the year 2008 against independent observations and a control run without data assimilation. The largest improvement in CO by assimilation of Measurements of Pollution in the Troposphere (MOPITT) CO columns is seen in the lower troposphere of the Northern Hemisphere (NH) extratropics during winter, and during the South African biomass-burning season. The assimilation of several O3 total column and stratospheric profile retrievals greatly improves the total column, stratospheric and upper tropospheric O3 analysis fields relative to the control run. The impact on lower tropospheric ozone, which comes from the residual of the total column and stratospheric profile O3 data, is smaller, but nevertheless there is some improvement particularly in the NH during winter and spring. The impact of the assimilation of tropospheric NO2 columns from the Ozone Monitoring Instrument (OMI) is small because of the short lifetime of NO2, suggesting that NO2 observations would be better used to adjust emissions instead of initial conditions. The results further indicate that the quality of the tropospheric analyses and of the stratospheric ozone analysis obtained with the C-IFS system has improved compared to the previous "coupled" model system of MACC.
    Full-text · Article · May 2015 · ATMOSPHERIC CHEMISTRY AND PHYSICS
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    ABSTRACT: In 1997 the International Maritime Organisation (IMO) adopted MARPOL Annex VI to prevent air pollution by shipping emissions. It regulates, among others, the sulphur content in shipping fuels which transforms into the air pollutant sulphur dioxide (SO2) during combustion. Within designated Sulphur Emission Control Areas (SECA), the sulphur content was limited to 1%, and on 1 January 2015, this limit was further reduced to 0.1%. Here we present the setup and measurement results of a permanent ship emission monitoring site near Hamburg harbour in the North Sea SECA. Trace gas measurements are conducted with in-situ instruments and a data set from September 2014 to January 2015 is presented. By combining measurements of carbon dioxide (CO2) and SO2 with ship position data, it is possible to deduce the sulphur fuel content of individual ships passing the measurement station, and thus, facilitating monitoring compliance of ships with the IMO regulations. While compliance is almost 100% for the 2014 data, it decreases only very little in 2015 to 95.4% despite the much stricter limit. We analysed more than 1400 ship plumes in total and for months with favourable conditions up to 40% of all ships entering and leaving Hamburg harbour could be checked for their sulphur fuel content.
    Full-text · Article · Apr 2015 · Atmospheric Chemistry and Physics

  • No preview · Article · Apr 2015
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    ABSTRACT: A representation of atmospheric chemistry has been included in the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). The new chemistry modules complement the aerosol modules of the IFS for atmospheric composition, which is named C-IFS. C-IFS for chemistry supersedes a coupled system in which chemical transport model (CTM) Model for OZone and Related chemical Tracers 3 was two-way coupled to the IFS (IFS-MOZART). This paper contains a description of the new on-line implementation, an evaluation with observations and a comparison of the performance of C-IFS with MOZART and with a re-analysis of atmospheric composition produced by IFS-MOZART within the Monitoring Atmospheric Composition and Climate (MACC) project. The chemical mechanism of C-IFS is an extended version of the Carbon Bond 2005 (CB05) chemical mechanism as implemented in CTM Transport Model 5 (TM5). CB05 describes tropospheric chemistry with 54 species and 126 reactions. Wet deposition and lightning nitrogen monoxide (NO) emissions are modelled in C-IFS using the detailed input of the IFS physics package. A 1 year simulation by C-IFS, MOZART and the MACC re-analysis is evaluated against ozonesondes, carbon monoxide (CO) aircraft profiles, European surface observations of ozone (O3), CO, sulfur dioxide (SO2) and nitrogen dioxide (NO2) as well as satellite retrievals of CO, tropospheric NO2 and formaldehyde. Anthropogenic emissions from the MACC/CityZen (MACCity) inventory and biomass burning emissions from the Global Fire Assimilation System (GFAS) data set were used in the simulations by both C-IFS and MOZART. C-IFS (CB05) showed an improved performance with respect to MOZART for CO, upper tropospheric O3, and wintertime SO2, and was of a similar accuracy for other evaluated species. C-IFS (CB05) is about 10 times more computationally efficient than IFS-MOZART.
    Full-text · Article · Apr 2015 · Geoscientific Model Development
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    ABSTRACT: The MACC III (Monitoring Atmospheric Composition and Climate III, http://www.copernicus-atmosphere.eu) project is establishing the core global and regional atmospheric environmental service delivered as a component of the European Earth observation programme Copernicus. The MACC global near-real time (NRT) service provides daily analyses and forecasts of trace gas and aerosol concentrations. This document presents the validation statistics and system evolution of the MACC NRT service for the period until 1 December 2014. This document is updated every 3 months.
    Full-text · Technical Report · Mar 2015
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    ABSTRACT: Monitoring Atmospheric Composition and Climate (MACC/MACCII) currently represents the European Union's Copernicus Atmosphere Monitoring Service (CAMS) (http://www.copernicus.eu), which will become fully operational in the course of 2015. The global near-real-time MACC model production run for aerosol and reactive gases provides daily analyses and 5 day forecasts of atmospheric composition fields. It is the only assimilation system world-wide that is operational to produce global analyses and forecasts of reactive gases and aerosol fields. We have investigated the ability of the MACC analysis system to simulate tropospheric concentrations of reactive gases (CO, O3, and NO2) covering the period between 2009 and 2012. A validation was performed based on CO and O3 surface observations from the Global Atmosphere Watch (GAW) network, O3 surface observations from the European Monitoring and Evaluation Programme (EMEP) and furthermore, NO2 tropospheric columns derived from the satellite sensors SCIAMACHY and GOME-2, and CO total columns derived from the satellite sensor MOPITT. The MACC system proved capable of reproducing reactive gas concentrations in consistent quality, however, with a seasonally dependent bias compared to surface and satellite observations: for northern hemispheric surface O3 mixing ratios, positive biases appear during the warm seasons and negative biases during the cold parts of the years, with monthly Modified Normalised Mean Biases (MNMBs) ranging between −30 and 30% at the surface. Model biases are likely to result from difficulties in the simulation of vertical mixing at night and deficiencies in the model's dry deposition parameterization. Observed tropospheric columns of NO2 and CO could be reproduced correctly during the warm seasons, but are mostly underestimated by the model during the cold seasons, when anthropogenic emissions are at a highest, especially over the US, Europe and Asia. Monthly MNMBs of the satellite data evaluation range between −110 and 40% for NO2 and at most −20% for CO, over the investigated regions. The underestimation is likely to result from a combination of errors concerning the dry deposition parameterization and certain limitations in the current emission inventories, together with an insufficiently established seasonality in the emissions.
    Full-text · Article · Mar 2015 · Atmospheric Chemistry and Physics
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    ABSTRACT: Daily global analyses and 5 day forecasts are generated in the context of the European Monitoring Atmospheric Composition and Climate (MACC) project using an extended version of the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF). IFS now includes modules for chemistry, deposition and emission of reactive gases, aerosols, and greenhouse gases, and the 4-dimensional variational data assimilation scheme makes use of multiple satellite observations of atmospheric composition in addition to meteorological observations. This paper describes the data assimilation setup of the new Composition-IFS (C-IFS) with respect to reactive gases and validates analysis fields of ozone (O3), carbon monoxide (CO), and nitrogen dioxide (NO2) for the year 2008 against independent observations and a control run without data assimilation. The largest improvement in CO by assimilation of MOPITT CO columns is seen in the lower troposphere of the Northern Hemisphere (NH) Extratropics during winter, and during the South African biomass burning season. The assimilation of several O3 total column and stratospheric profile retrievals greatly improves the total column, stratospheric and upper tropospheric O3 analysis fields relative to the control run. The impact on lower tropospheric ozone, which comes from the residual of the total column and stratospheric profile O3 data, is smaller, but nevertheless there is some improvement particularly in the NH during winter and spring. The impact of the assimilation of OMI tropospheric NO2 columns is small because of the short lifetime of NO2, suggesting that NO2 observations would be better used to adjust emissions instead of initial conditions. The results further indicate that the quality of the tropospheric analyses and of the stratospheric ozone analysis obtained with the C-IFS system has improved compared to the previous "coupled" model system of MACC.
    Full-text · Article · Feb 2015 · Atmospheric Chemistry and Physics
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    ABSTRACT: The European MACC (Monitoring Atmospheric Composition and Climate) project is preparing the operational Copernicus Atmosphere Monitoring Service (CAMS), one of the services of the European Copernicus Programme on Earth observation and environmental services. MACC uses data assimilation to combine in-situ and remote sensing observations with global and regional models of atmospheric reactive gases, aerosols and greenhouse gases, and is based on the Integrated Forecast System of the ECMWF. The global component of the MACC service has a dedicated validation activity to document the quality of the atmospheric composition products. In this paper we discuss the approach to validation that has been developed over the past three years. Topics discussed are the validation requirements, the operational aspects, the measurement data sets used, the structure of the validation reports, the models and assimilation systems validated, the procedure to introduce new upgrades, and the scoring methods. One specific target of the MACC system concerns forecasting special events with high pollution concentrations. Such events receive extra attention in the validation process. Finally, a summary is provided of the results from the validation of the latest set of daily global analysis and forecast products from the MACC system reported in November 2014.
    Full-text · Article · Feb 2015 · Geoscientific Model Development Discussions
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    ABSTRACT: Measurements by the Ozone Monitoring Instrument (OMI) on board the Aura satellite have been used to retrieve global maps of glyoxal (CHOCHO) columns by applying the Differential Optical Absorption Spectroscopy (DOAS) method. Large amounts of glyoxal are found over regions with high biogenic emissions and vegetation fires, as well as over highly populated areas with large anthropogenic emissions. This paper focuses on investigating the link between CHOCHO columns and biogenic emissions during 2005-2012. The largest correlations are observed over the Southeastern US and the North of Africa, where large vegetation areas are found. Moreover, negative correlation are found over African regions where large fire events occur.
    No preview · Article · Jan 2015
  • Stefan F. Schreier · Andreas Richter · John P. Burrows
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    ABSTRACT: Vegetation fires across the globe, either started by lightning strikes or caused by humans, have various impacts on Earth systems such as the atmosphere and biosphere. A simple statistical approach to estimate emission factors (EFs) of NOx, based on the empirical relationship between satellite-observed tropospheric NO2 vertical columns (TVC NO2) and fire radiative power (FRP), is presented. The great advantage of the method is the partitioning of different NOx emission sourcesand the application to various biomes and regions. The estimated NOx EFs are 1.83, 1.48, 2.96, and 0.72 g kg-1 for tropical forest, savanna and grassland, crop residue, and boreal forest, respectively. There is overall agreement between the satellitederived EFs and comparable values reported in the literature, suggesting that the assumptions made in the approach are reasonable. However, a substantial discrepancy is found for savanna and grassland, which is the most frequently burned land cover type on Earth. Possible implications of these differences for fire emission inventories are discussed.
    No preview · Article · Jan 2015
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    ABSTRACT: Ozone depletion events in the polar troposphere have been linked to extremely high concentrations of bromine, known as bromine explosion events (BEE). However, the optimum meteorological conditions for the occurrence of these events remain uncertain. On 4-5 April 2011, a combination of both blowing snow and a stable shallow boundary layer was observed during a BEE at Eureka, Canada (86.4°W, 80.1°N). Measurements made by a Multi-Axis Differential Optical Absorption Spectroscopy spectrometer were used to retrieve BrO profiles and partial columns. During this event, the near-surface BrO volume mixing ratio increased to ~20parts per trillion by volume, while ozone was depleted to ~1ppbv from the surface to 700m. Back trajectories and Global Ozone Monitoring Experiment-2 satellite tropospheric BrO columns confirmed that this event originated from a bromine explosion over the Beaufort Sea. From 30 to 31 March, meteorological data showed high wind speeds (24m/s) and elevated boundary layer heights (~800m) over the Beaufort Sea. Long-distance transportation (~1800km over 5days) to Eureka indicated strong recycling of BrO within the bromine plume. This event was generally captured by a global chemistry-climate model when a sea-salt bromine source from blowing snow was included. A model sensitivity study indicated that the surface BrO at Eureka was controlled by both local photochemistry and boundary layer dynamics. Comparison of the model results with both ground-based and satellite measurements confirmed that the BEE observed at Eureka was triggered by transport of enhanced BrO from the Beaufort Sea followed by local production/recycling under stable atmospheric shallow boundary layer conditions.
    No preview · Article · Jan 2015 · Journal of Geophysical Research Atmospheres
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    Full-text · Technical Report · Dec 2014

Publication Stats

11k Citations
913.76 Total Impact Points

Institutions

  • 1970-2015
    • Universität Bremen
      • Institut für Umweltphysik (IUP)
      Bremen, Bremen, Germany
  • 2011
    • University of Toronto
      • Department of Physics
      Toronto, Ontario, Canada
  • 2008
    • Norwegian Institute for Air Research
      Kristiania (historical), Oslo County, Norway
  • 2007
    • German Aerospace Center (DLR)
      • Remote Sensing Technology Institute (IMF)
      Köln, North Rhine-Westphalia, Germany
  • 2004
    • Universität Heidelberg
      • Institute of Environmental Physics
      Heidelburg, Baden-Württemberg, Germany