Folkard Wittrock

Folkard Wittrock
Universität Bremen | Uni Bremen · Institute of Environmental Physics

Dr.

About

252
Publications
29,921
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Introduction
Currently, I'm coordinating a project called MeSmarT (Measurements of shipping emissions in the marine troposphere) to estimate the influence of ship emissions on the chemistry of the atmospheric boundary layer over the North and Baltic Sea. The project has been established in cooperation with the German Bundesamt für Seeschifffahrt und Hydrographie (Federal Maritime and Hydrographic Agency) and the Helmholtz Centre Geesthacht. See also www.mesmart.de
Additional affiliations
January 1995 - present
Universität Bremen
Position
  • Senior Researcher

Publications

Publications (252)
Article
Full-text available
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...
Article
Full-text available
In November 2011, ship-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed within the SHIVA campaign on board RV Sonne in the South China and Sulu Sea. Spectral measurements for a total of eleven days could be used to retrieve tropospheric slant column densities (SCDs) of nitrogen dioxide (NO2) and s...
Article
Full-text available
It is well-known that spectral effects of liquid water are present in absorption (DOAS) measurements above the ocean and insufficiently removed liquid water structures may interfere with trace gas absorptions leading to wrong (sometimes even non-physical) results. Currently available literature cross-sections of liquid water absorption are provided...
Article
Full-text available
Satellite observations from the SCIAMACHY, GOME-2 and OMI spectrometers have been used to retrieve atmospheric columns of glyoxal (CHOCHO) with the DOAS method. High CHOCHO levels were found over regions with large biogenic and pyrogenic emissions, and hot-spots have been identified over areas of anthropogenic activities. This study focuses on the...
Article
Full-text available
Tropospheric BrO was measured by a ground-based remote-sensing spectrometer at Halley in Antarctica in spring 2007, and BrO was measured by satellite-borne remote-sensing spectrometers using similar spectral regions and similar Differential Optical Absorption Spectroscopy (DOAS) analyses. Near-surface BrO was simultaneously measured in situ at Hall...
Article
Full-text available
Inland ships are an important source of NOx, especially for cities along busy waterways. The amount and effect of such emissions depend on the traffic density and NOx emission rates of individual vessels. Ship emission rates are typically derived using in situ land measurements in relation to NOx emission factors (e.g. the number of pollutants emit...
Article
Full-text available
Airborne imaging differential optical absorption spectroscopy (DOAS), ground-based stationary DOAS, and car DOAS measurements were conducted during the S5P-VAL-DE-Ruhr campaign in September 2020. The campaign area is located in the Rhine-Ruhr region of North Rhine-Westphalia, western Germany, which is a pollution hotspot in Europe comprising urban...
Preprint
Full-text available
Airborne imaging differential optical absorption spectroscopy (DOAS), ground-based stationary and car DOAS measurements were conducted during the S5P-VAL-DE-Ruhr campaign in September 2020. The campaign area is located in the Rhine-Ruhr region of North Rhine-Westphalia, Western Germany, which is a pollution hotspot in Europe comprising urban and la...
Preprint
Full-text available
Inland ships are an important source of NOx, especially for cities along busy waterways. The amount and effect of these emissions depends on the traffic density and the NOx emission rates of the individual vessels. Monitoring of ship emissions is usually carried out using in situ instruments on land and often relative NOx emission factors, e.g. the...
Article
Full-text available
This paper reports on ground-based validation of the atmospheric OClO data record produced within the framework of EUMETSAT's Satellite Application Facility on Atmospheric Chemistry Monitoring (AC SAF) using the Global Ozone Monitoring Experiment (GOME)-2A and GOME-2B instrument measurements, covering the 2007–2016 and 2013–2016 periods, respective...
Preprint
Full-text available
This paper reports on ground-based validation of the atmospheric OClO data record produced in the framework of EUMETSAT’s Satellite Application Facility on Atmospheric Chemistry Monitoring (AC SAF) using the GOME2-A and -B instruments over the 2007–2016 and 2013–2016 periods, respectively. OClO slant column densities are compared to correlative mea...
Preprint
Full-text available
Ships are an important source of SO2 and NOx, which are key parameters of air quality. Monitoring of ship emissions is usually carried out using in situ instruments on land, which depend on favourable wind conditions to transport the emitted substances to the measurement site. Remote sensing techniques such as long path DOAS (LP-DOAS) measurements...
Article
Full-text available
This paper reports on consolidated ground-based validation results of the atmospheric NO2 data produced operationally since April 2018 by the TROPOspheric Monitoring Instrument (TROPOMI) on board of the ESA/EU Copernicus Sentinel-5 Precursor (S5P) satellite. Tropospheric, stratospheric, and total NO2 column data from S5P are compared to correlative...
Article
Full-text available
The second Cabauw Intercomparison of Nitrogen Dioxide measuring Instruments (CINDI-2) took place in Cabauw (the Netherlands) in September 2016 with the aim of assessing the consistency of multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of tropospheric species (NO2, HCHO, O3, HONO, CHOCHO and O4). This was achieved th...
Article
Full-text available
Multi-axis differential optical absorption spectroscopy (MAX-DOAS) and direct sun NO2 vertical column network data are used to investigate the accuracy of tropospheric NO2 column measurements of the GOME-2 instrument on the MetOp-A satellite platform and the OMI instrument on Aura. The study is based on 23 MAX-DOAS and 16 direct sun instruments at...
Article
Full-text available
Multi-axis differential optical absorption spectroscopy (MAX-DOAS) and direct sun NO2 vertical column network data are used to investigate the accuracy of tropospheric NO2 column measurements of the GOME-2 instrument on the MetOp-A satellite platform and the OMI instrument on Aura. The study is based on 23 MAX-DOAS and 16 direct sun instruments at...
Presentation
Full-text available
Bessere Erfassung der Emissionen der Binnenschiffe
Preprint
Full-text available
Abstract. This paper reports on consolidated ground-based validation results of the atmospheric NO<sub>2</sub> data produced operationally since April 2018 by the TROPOMI instrument on board of the ESA/EU Copernicus Sentinel-5 Precursor (S5p) satellite. Tropospheric, stratospheric, and total NO<sub>2</sub> column data from S5p are compared to corre...
Article
Full-text available
In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17 d during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, the Netherlands (51.97∘ N, 4.93∘ E). We report on the outcome of the formal semi-blind intercomp...
Article
Full-text available
In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17 d during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, the Netherlands (51.97∘ N, 4.93∘ E). We report on the outcome of the formal semi-blind intercomp...
Preprint
Full-text available
Abstract. MAX-DOAS and direct sun NO<sub>2</sub> vertical column network data are used to investigate the accuracy of tropospheric NO<sub>2</sub> column measurements of the GOME-2 instrument on the MetOP-A satellite platform and the OMI instrument on Aura. The study is based on 23 MAX-DOAS and 16 direct sun instruments at stations distributed world...
Preprint
Full-text available
Abstract. Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a well-established ground-based measurement technique for the detection of aerosols and trace gases particularly in the boundary layer and the lower troposphere: ultraviolet- and visible radiation spectra of skylight are analysed to obtain information on different atmos...
Article
Full-text available
This study describes a novel application of an “onion-peeling” approach to multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of shipping emissions aiming at investigating the strong horizontal inhomogeneities in NO2 over a shipping lane. To monitor ship emissions on the main shipping route towards the port of Hamburg,...
Article
Full-text available
Trace gas maps retrieved from satellite measurements show enhanced levels of the atmospheric volatile organic compounds formaldehyde (HCHO) and glyoxal (CHOCHO) over the Atlantic Ocean. To validate the spatial distribution of this continental outflow, ship-based measurements were taken during the Continental Outflow of Pollutants towards the MArine...
Article
Full-text available
A novel imaging-DOAS (differential optical absorption spectroscopy) instrument IMPACT (Imaging MaPper for AtmospheriC observaTions) is presented combining full-azimuthal pointing (360∘) with a large vertical coverage (∼41∘). Complete panoramic scans are acquired at a temporal resolution of ∼15 min, enabling the retrieval of NO2 vertical profiles ov...
Article
Full-text available
A novel imaging-DOAS instrument (IMPACT) is presented combining full-azimuthal pointing (360°) with a large vertical coverage (~ 40°). Complete panoramic scans are acquired at a temporal resolution of ~ 15 minutes enabling the retrieval of NO2 vertical profiles over the entire panorama around the measurement site. IMPACT showed excellent agreement...
Article
Full-text available
Trace gas maps retrieved from satellite measurements show enhanced levels of the atmospheric volatile organic compounds formaldehyde (HCHO) and glyoxal (CHOCHO) over the Atlantic Ocean. To validate the spatial distribution of this continental outflow, ship-based measurements were taken during the project Continental Outflow of Pollutants towards th...
Article
Full-text available
We present a new MAX-DOAS profiling algorithm for aerosols and trace gases, BOREAS, which utilizes an iterative solution method including Tikhonov regularization and the optimal estimation technique. The aerosol profile retrieval is based on a novel approach in which the absorption depth of O4 is directly used in order to retrieve extinction coeffi...
Article
Full-text available
This study describes a novel application of an onion peeling like approach to MAX-DOAS measurements of shipping emissions aiming at investigating the strong horizontal inhomogeneities in NO2 over a shipping lane. To monitor ship emissions on the main shipping route towards the port of Hamburg, a two-channel (UV and visible) MAX-DOAS instrument was...
Article
Full-text available
We present a new MAX-DOAS profiling algorithm for aerosols and trace gases, BOREAS, which utilizes an iterative solution method including Tikhonov regularization and the optimal estimation technique. Performance tests are separated into two parts. First, we address the general sensitivity of the retrieval on the example of synthetic data calculated...
Article
Full-text available
A 3-year time series of ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of NO2 and SO2 on the island Neuwerk has been analyzed for contributions from shipping emissions. The island is located in the German Bight, close to the main shipping lane (at a distance of 6–7 km) into the river Elbe towards the ha...
Article
Full-text available
The differential optical absorption spectroscopy (DOAS) method is a well-known remote sensing technique that is nowadays widely used for measurements of atmospheric trace gases, creating the need for harmonization and characterization efforts. In this study, an intercomparison exercise of DOAS retrieval codes from 17 international groups is present...
Article
Full-text available
Long-range transport followed by deposition of black carbon on glaciers of Tibet is one of the key issues of climate research as it induces changes on radiative forcing and subsequently impacting the melting of glaciers. The transport mechanism, however, is not well understood. In this study, we use short-lived reactive aromatics as proxies to diag...
Article
Full-text available
A three-year time series of ground-based MAX-DOAS measurements of NO2 and SO2 on the island Neuwerk has been analyzed for contributions from shipping emissions. The island is located in the German Bight, close to the main shipping lane into the river Elbe towards the harbor of Hamburg. Measurements of individual ship plumes as well as of background...
Article
Full-text available
The Differential Optical Absorption Spectroscopy (DOAS) method is a well-known remote sensing technique that is nowadays widely used for measurements of atmospheric trace gases, creating the need for harmonization and characterization efforts. In this study, an intercomparison exercise of DOAS retrieval codes from 17 international groups is present...
Poster
Full-text available
Over the last years, ground-based MAXDOAS measurements have played an increasing role for the ground truthing of space-nadir observations of air quality relevant trace gases such as NO2 and HCHO. Current MAXDOAS network data however lack harmonization in terms of data acquisition, data processing and data reporting. This issue is addressed as part...
Article
Full-text available
Long-range transport and subsequent deposition of black carbon on glaciers of Tibet is one of the key issues of climate research inducing changes on radiative forcing and subsequently impacting on the melting of glaciers. The transport mechanism, however, is not well understood. In this study, we use short-lived reactive aromatics as proxies to dia...
Article
Slant column (SC) densities of nitrogen dioxide (NO2), formaldehyde (HCHO), glyoxal (CHOCHO) and oxygen dimer (O4) were successfully retrieved for the first time in Athens, by using spectral measurements from a ground-based multi-azimuth Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) system. The data span the period from October...
Article
Full-text available
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 geomet...
Article
Full-text available
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 geomet...
Article
Full-text available
In 1997 the International Maritime Organisation (IMO) adopted MARPOL Annex VI to prevent air pollution by shipping emissions. It regulates, among other issues, the sulfur content in shipping fuels, which is transformed into the air pollutant sulfur dioxide (SO2) during combustion. Within designated Sulfur Emission Control Areas (SECA), the sulfur c...
Conference Paper
Full-text available
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 n...
Article
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 pop...
Conference Paper
Full-text available
Total and tropospheric NO 2 columns have been operationally retrieved from the GOME-2/MetOp instruments since the first MetOp platform was put in orbit in October 2006. GOME-2 NO 2 data products are retrieved in three main steps: (1) a DOAS spectral analysis yielding the total column amount of NO 2 along the slant optical path, (2) an estimation of...
Article
Full-text available
Satellite observations from the SCIAMACHY, GOME-2, and OMI spectrometers have been used to retrieve atmospheric columns of glyoxal (CHOCHO) with the DOAS method. High CHOCHO levels are found over regions with large biogenic and pyrogenic emissions, and hot-spots have been identified over areas of anthropogenic activities. This study focuses on the...
Article
Full-text available
Glyoxal is an important intermediate species formed by the oxidation of common biogenic and anthropogenic volatile organic compounds such as isoprene, toluene and acetylene. Although glyoxal has been shown to play an important role in urban and forested environments, its role in the open ocean environment is still not well understood, with only a f...
Article
Full-text available
It is well-known that spectral effects of liquid water are present in absorption (DOAS) measurements above the ocean and insufficiently removed liquid water structures may interfere with trace gas absorptions leading to wrong (sometimes even non-physical) results. Currently available literature cross-sections of liquid water absorption are provided...
Article
Full-text available
Record breaking loss of ozone (O3) in the Arctic stratosphere has been reported in winter–spring 2010/2011. We examine in detail the composition and transformations occurring in the Arctic polar vortex using total column and vertical profile data products for O3, bromine oxide (BrO), nitrogen dioxide (NO2), chlorine dioxide (OClO), and polar strato...
Conference Paper
Since the establishment of the SCIAMACHY Quality Working Group (SQWG) in a joint inter-agency ESA-DLR-NSO effort in late 2006, the ESA operational Level 2 processor was significantly improved w.r.t. data quality and the product list was substantially enhanced with new parameters. Current operational Level 2 products correspond to version 5. Meanwhi...
Article
Full-text available
Record breaking losses of ozone (O3) in the Arctic stratosphere have been reported in winter and spring 2011. Trace gas amounts and polar stratospheric cloud (PSC) distributions retrieved using differential optical absorption spectroscopy (DOAS) and scattering theory applied to the measurements of radiance and irradiance by satellite-born and groun...