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Article ; Online: OClO as observed by TROPOMI

J. Puķīte / C. Borger / S. Dörner / M. Gu / T. Wagner

Atmospheric Chemistry and Physics, Vol 22, Pp 245-

a comparison with meteorological parameters and polar stratospheric cloud observations

2022 Volume 272

Abstract: Chlorine dioxide (OClO) is a by-product of the ozone-depleting halogen chemistry in the stratosphere. Although it is rapidly photolysed at low solar zenith angles (SZAs), it plays an important role as an indicator of the chlorine activation in polar ... ...

Abstract	Chlorine dioxide (OClO) is a by-product of the ozone-depleting halogen chemistry in the stratosphere. Although it is rapidly photolysed at low solar zenith angles (SZAs), it plays an important role as an indicator of the chlorine activation in polar regions during polar winter and spring at twilight conditions because of the nearly linear dependence of its formation on chlorine oxide (ClO). Here, we compare slant column densities (SCDs) of chlorine dioxide (OClO) retrieved by means of differential optical absorption spectroscopy (DOAS) from spectra measured by the TROPOspheric Monitoring Instrument (TROPOMI) with meteorological data for both Antarctic and Arctic regions for the first three winters in each of the hemispheres (November 2017–October 2020). TROPOMI, a UV–Vis–NIR–SWIR instrument on board of the Sentinel-5P satellite, monitors the Earth's atmosphere in a near-polar orbit at an unprecedented spatial resolution and signal-to-noise ratio and provides daily global coverage at the Equator and thus even more frequent observations at polar regions. The observed OClO SCDs are generally well correlated with the meteorological conditions in the polar winter stratosphere; for example, the chlorine activation signal appears as a sharp gradient in the time series of the OClO SCDs once the temperature drops to values well below the nitric acid trihydrate (NAT) existence temperature ( T NAT ). Also a relation of enhanced OClO values at lee sides of mountains can be observed at the beginning of the winters, indicating a possible effect of lee waves on chlorine activation. The dataset is also compared with CALIPSO Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) polar stratospheric cloud (PSC) observations. In general, OClO SCDs coincide well with CALIOP measurements for which PSCs are detected. Very high OClO levels are observed for the northern hemispheric winter 2019/20, with an extraordinarily long period with a stable polar vortex being even close to the values found for southern hemispheric winters. An ...
Keywords	Physics ; QC1-999 ; Chemistry ; QD1-999
Subject code	551
Language	English
Publishing date	2022-01-01T00:00:00Z
Publisher	Copernicus Publications
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Identification of atmospheric and oceanic teleconnection patterns in a 20-year global data set of the atmospheric water vapour column measured from satellites in the visible spectral range

T. Wagner / S. Beirle / S. Dörner / C. Borger / R. Van Malderen

Atmospheric Chemistry and Physics, Vol 21, Pp 5315-

2021 Volume 5353

Abstract: We used a global long-term (1995–2015) data set of total column water vapour (TCWV) derived from satellite observations to quantify to which extent the temporal patterns of various teleconnections can be identified in this data set. To our knowledge, ... ...

Abstract	We used a global long-term (1995–2015) data set of total column water vapour (TCWV) derived from satellite observations to quantify to which extent the temporal patterns of various teleconnections can be identified in this data set. To our knowledge, such a comprehensive global TCWV data set was rarely used for teleconnection studies. One important property of the TCWV data set is that it is purely based on observational data. We developed a new empirical method to decide whether a teleconnection index is significantly detected in the global data set. We compared our new method to well-established hypothesis tests and found good agreement with the results of our approach. Based on our empirical method more than 40 teleconnection indices were significantly detected in the global TCWV data set derived from satellite observations. In addition to the satellite data we also applied our method to other global data sets derived from ERA-Interim. One important finding is that the spatial patterns obtained for the ERA TCWV data are very similar to the observational TCWV data set indicating a high consistency between the satellite and ERA data. Moreover, similar results are also found for two selections of ERA data (either all data or mainly clear-sky data). This finding indicates that the clear-sky bias of the satellite data set is negligible for the results of this study. However, for some indices, also systematic differences in the spatial patterns between the satellite and model data set were found probably indicating possible shortcomings in the model data. For most “traditional” teleconnection data sets (surface temperature, surface pressure, geopotential heights and meridional winds at different altitudes) a smaller number of significant teleconnection indices was found than for the TCWV data sets, while for zonal winds at different altitudes, the number of significant teleconnection indices (up to > 50) was higher. The strongest teleconnection signals were found in the data sets of tropospheric geopotential heights and surface pressure. In all global data sets, no “other indices” (solar variability, stratospheric AOD or hurricane frequency) were significantly detected. Since many teleconnection indices are strongly correlated, we also applied our method to a set of orthogonalised indices, which represent the dominant independent temporal teleconnection patterns. The number of significantly detected orthogonalised indices (20) was found to be much smaller than for the original indices (42). Based on the orthogonalised indices we derived the global spatial distribution of the cumulative effect of teleconnections. The strongest effect on the TCWV is found in the tropics and high latitudes.
Keywords	Physics ; QC1-999 ; Chemistry ; QD1-999
Subject code	551
Language	English
Publishing date	2021-04-01T00:00:00Z
Publisher	Copernicus Publications
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: SO 2 and BrO emissions of Masaya volcano from 2014 to 2020

F. Dinger / T. Kleinbek / S. Dörner / N. Bobrowski / U. Platt / T. Wagner / M. Ibarra / E. Espinoza

Atmospheric Chemistry and Physics, Vol 21, Pp 9367-

2021 Volume 9404

Abstract: Masaya (Nicaragua, 12.0 ∘ N, 86.2 ∘ W; 635 m a.s.l.) is one of the few volcanoes hosting a lava lake, today. This study has two foci: (1) discussing the state of the art of long-term SO 2 emission flux monitoring with the example of Masaya and (2) the ... ...

Abstract	Masaya (Nicaragua, 12.0 ∘ N, 86.2 ∘ W; 635 m a.s.l.) is one of the few volcanoes hosting a lava lake, today. This study has two foci: (1) discussing the state of the art of long-term SO 2 emission flux monitoring with the example of Masaya and (2) the provision and discussion of a continuous data set on volcanic gas data with a large temporal coverage, which is a major extension of the empirical database for studies in volcanology as well as atmospheric bromine chemistry. We present time series of SO 2 emission fluxes and <math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">BrO</mi><mo>/</mo><msub><mi mathvariant="normal">SO</mi><mn mathvariant="normal">2</mn></msub></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="48pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="6b1ff19dbad33dbc3d45406e919bea5c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00001.svg" width="48pt" height="14pt" src="acp-21-9367-2021-ie00001.png"/></svg:svg> molar ratios in the gas plume of Masaya from March 2014 to March 2020 – covering the three time periods (1) before the lava lake appearance, (2) a period of high lava lake activity (November 2015 to May 2018), and (3) after the period of high lava lake activity. For these three time periods, we report average SO 2 emission fluxes of ( 1000±200 ), ( 1000±300 ), and ( 700±200 ) t d −1 and average <math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">BrO</mi><mo>/</mo><msub><mi mathvariant="normal">SO</mi><mn mathvariant="normal">2</mn></msub></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="48pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e30adbcd92590ca9ce606f6a49723a9d"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00002.svg" width="48pt" height="14pt" src="acp-21-9367-2021-ie00002.png"/></svg:svg> molar ratios of <math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">2.9</mn><mo>±</mo><mn mathvariant="normal">1.5</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">5</mn></mrow></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="85pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="831e375d74d8c0d303177f1252004bbd"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00003.svg" width="85pt" height="15pt" src="acp-21-9367-2021-ie00003.png"/></svg:svg> , <math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">4.8</mn><mo>±</mo><mn mathvariant="normal">1.9</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">5</mn></mrow></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="85pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="770134696f9d876c04ec2e8a97853f54"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00004.svg" width="85pt" height="15pt" src="acp-21-9367-2021-ie00004.png"/></svg:svg> , and <math xmlns="http://www.w3.org/1998/Math/MathML" id="M16" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>(</mo><mn mathvariant="normal">5.5</mn><mo>±</mo><mn mathvariant="normal">2.6</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">5</mn></mrow></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="85pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="65ccbd3454413ca5cdea9787a7d0beac"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00005.svg" width="85pt" height="15pt" src="acp-21-9367-2021-ie00005.png"/></svg:svg> . Our SO 2 emission flux retrieval is based on a comprehensive investigation of various aspects of spectroscopic retrievals, the wind conditions, and the plume height. We observed a correlation between the SO 2 emission fluxes and the wind speed in the raw data. We present a partial correction of this artefact by applying dynamic estimates for the plume height as a function of the wind speed. Our retrieved SO 2 emission fluxes are on average a factor of 1.4 larger than former estimates based on the same data. Further, we observed different patterns in the <math xmlns="http://www.w3.org/1998/Math/MathML" id="M20" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">BrO</mi><mo>/</mo><msub><mi mathvariant="normal">SO</mi><mn mathvariant="normal">2</mn></msub></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="48pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="9430ed9c4253e10006c839c470924f64"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00006.svg" width="48pt" height="14pt" src="acp-21-9367-2021-ie00006.png"/></svg:svg> time series: (1) an annual cyclicity with amplitudes between 1.4 and <math xmlns="http://www.w3.org/1998/Math/MathML" id="M21" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">2.5</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">5</mn></mrow></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="51pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="8160105bd78af28c8574c8849ced7339"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00007.svg" width="51pt" height="13pt" src="acp-21-9367-2021-ie00007.png"/></svg:svg> and a weak semi-annual modulation, (2) a step increase by <math xmlns="http://www.w3.org/1998/Math/MathML" id="M22" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">0.7</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">5</mn></mrow></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="51pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="1c5594f7a413bfdd8734d6e11ef1044f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00008.svg" width="51pt" height="13pt" src="acp-21-9367-2021-ie00008.png"/></svg:svg> in late 2015, (3) a linear trend of <math xmlns="http://www.w3.org/1998/Math/MathML" id="M23" display="inline" overflow="scroll" dspmath="mathml"><mrow><mn mathvariant="normal">1.4</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">5</mn></mrow></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="51pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="9bc2f029791fcdea103317942d27ed33"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00009.svg" width="51pt" height="13pt" src="acp-21-9367-2021-ie00009.png"/></svg:svg> per year from November 2015 to March 2018, and (4) a linear trend of <math xmlns="http://www.w3.org/1998/Math/MathML" id="M24" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">0.8</mn><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">5</mn></mrow></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="59pt" height="13pt" class="svg-formula" dspmath="mathimg" md5hash="9eb890aaf64466b550110a6e60c5f0c1"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00010.svg" width="59pt" height="13pt" src="acp-21-9367-2021-ie00010.png"/></svg:svg> per year from June 2018 to March 2020. The step increase in 2015 coincided with the lava lake appearance and was thus most likely caused by a change in the magmatic system. We suggest that the cyclicity might be a manifestation of meteorological cycles. We found an anti-correlation between the <math xmlns="http://www.w3.org/1998/Math/MathML" id="M25" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">BrO</mi><mo>/</mo><msub><mi mathvariant="normal">SO</mi><mn mathvariant="normal">2</mn></msub></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="48pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="7507ad34a1a47c238c3486bfe3773e42"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00011.svg" width="48pt" height="14pt" src="acp-21-9367-2021-ie00011.png"/></svg:svg> molar ratios and the atmospheric water concentration (correlation coefficient of −0.47 ) but, in contrast to that, neither a correlation with the ozone mixing ratio ( +0.21 ) nor systematic dependencies between the <math xmlns="http://www.w3.org/1998/Math/MathML" id="M28" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">BrO</mi><mo>/</mo><msub><mi mathvariant="normal">SO</mi><mn mathvariant="normal">2</mn></msub></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="48pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="81ca8d0618b2f5a1e0f4cc515ca9ed69"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-21-9367-2021-ie00012.svg" width="48pt" height="14pt" src="acp-21-9367-2021-ie00012.png"/></svg:svg> molar ratios and the atmospheric plume age for an age range of 2–20 min after the release from the volcanic edifice. The two latter observations indicate an early stop of the autocatalytic transformation of bromide Br − solved in aerosol particles to atmospheric BrO.
Keywords	Physics ; QC1-999 ; Chemistry ; QD1-999
Language	English
Publishing date	2021-06-01T00:00:00Z
Publisher	Copernicus Publications
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Technical note

X. Tian / Y. Wang / S. Beirle / P. Xie / T. Wagner / J. Xu / A. Li / S. Dörner / B. Ren / X. Li

Atmospheric Chemistry and Physics, Vol 21, Pp 12867-

Evaluation of profile retrievals of aerosols and trace gases for MAX-DOAS measurements under different aerosol scenarios based on radiative transfer simulations

2021 Volume 12894

Abstract: Ground-based Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a state-of-the-art remote sensing technique for deriving vertical profiles of trace gases and aerosols. However, MAX-DOAS profile inversions under aerosol pollution ... ...

Abstract	Ground-based Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) is a state-of-the-art remote sensing technique for deriving vertical profiles of trace gases and aerosols. However, MAX-DOAS profile inversions under aerosol pollution scenarios are challenging because of the complex radiative transfer and limited information content of the measurements. In this study, the performances of two inversion algorithms were evaluated for various aerosol pollution scenarios based on synthetic slant column densities (SCDs) derived from radiative transfer simulations. Compared to previous studies, in our study, much larger ranges of aerosol optical depth (AOD) and NO 2 vertical column densities (VCDs) are covered. One inversion algorithm is based on optimal estimation; the other uses a parameterized approach. In this analysis, three types of profile shapes for aerosols and NO 2 were considered: exponential, Boltzmann, and Gaussian. First, the systematic deviations of the retrieved aerosol profiles from the input profiles were investigated. For most cases, the AODs of the retrieved profiles were found to be systematically lower than the input values, and the deviations increased with increasing AOD. In particular for the optimal estimation algorithm and for high AOD, these findings are consistent with the results in previous studies. The assumed single scattering albedo (SSA) and asymmetry parameter (AP) have a systematic influence on the aerosol retrieval. However, for most cases the influence of the assumed SSA and AP on the retrieval results are rather small (compared to other uncertainties). For the optimal estimation algorithm, the agreement with the input values can be improved by optimizing the covariance matrix of the a priori uncertainties. Second, the aerosol effects on the NO 2 profile retrieval were tested. Here, especially for the optimal estimation algorithm, a systematic dependence on the NO 2 VCD was found, with a strong relative overestimation of the retrieved results for low NO 2 VCDs and an ...
Keywords	Physics ; QC1-999 ; Chemistry ; QD1-999
Subject code	290
Language	English
Publishing date	2021-08-01T00:00:00Z
Publisher	Copernicus Publications
Document type	Article ; Online
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Article ; Online: Long-term MAX-DOAS measurements of NO 2 , HCHO, and aerosols and evaluation of corresponding satellite data products over Mohali in the Indo-Gangetic Plain

V. Kumar / S. Beirle / S. Dörner / A. K. Mishra / S. Donner / Y. Wang / V. Sinha / T. Wagner

Atmospheric Chemistry and Physics, Vol 20, Pp 14183-

2020 Volume 14235

Abstract: We present comprehensive long-term ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of aerosols, nitrogen dioxide (NO 2 ), and formaldehyde (HCHO) from Mohali (30.667 ∘ N, 76.739 ∘ E; ∼310 m above mean sea ... ...

Abstract	We present comprehensive long-term ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements of aerosols, nitrogen dioxide (NO 2 ), and formaldehyde (HCHO) from Mohali (30.667 ∘ N, 76.739 ∘ E; ∼310 m above mean sea level), located in the densely populated Indo-Gangetic Plain (IGP) of India. We investigate the temporal variation in tropospheric columns, surface volume mixing ratio (VMR), and vertical profiles of aerosols, NO 2 , and HCHO and identify factors driving their ambient levels and distributions for the period from January 2013 to June 2017. We observed mean aerosol optical depth (AOD) at 360 nm, tropospheric NO 2 vertical column density (VCD), and tropospheric HCHO VCD for the measurement period to be 0.63 ± 0.51, (6.7 ± 4.1) × 10 15 , and (12.1 ± 7.5) × 10 15 molecules cm −2 , respectively. Concerning the tropospheric NO 2 VCDs, Mohali was found to be less polluted than urban and suburban locations of China and western countries, but comparable HCHO VCDs were observed. For the more than 4 years of measurements during which the region around the measurement location underwent significant urban development, we did not observe obvious annual trends in AOD, NO 2 , and HCHO. High tropospheric NO 2 VCDs were observed in periods with enhanced biomass and biofuel combustion (e.g. agricultural residue burning and domestic burning for heating). Highest tropospheric HCHO VCDs were observed in agricultural residue burning periods with favourable meteorological conditions for photochemical formation, which in previous studies have shown an implication for high ambient ozone also over the IGP. Highest AOD is observed in the monsoon season, indicating possible hygroscopic growth of the aerosol particles. Most of the NO 2 is located close to the surface, whereas significant HCHO is present at higher altitudes up to 600 m during summer indicating active photochemistry at high altitudes. The vertical distribution of aerosol, NO 2 , and HCHO follows the change in boundary layer height ...
Keywords	Physics ; QC1-999 ; Chemistry ; QD1-999
Subject code	333 ; 511
Language	English
Publishing date	2020-11-01T00:00:00Z
Publisher	Copernicus Publications
Document type	Article ; Online
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Article ; Online: NO x lifetimes and emissions of cities and power plants in polluted background estimated by satellite observations

F. Liu / S. Beirle / Q. Zhang / S. Dörner / K. He / T. Wagner

Atmospheric Chemistry and Physics, Vol 16, Pp 5283-

2016 Volume 5298

Abstract: We present a new method to quantify NO x emissions and corresponding atmospheric lifetimes from OMI NO 2 observations together with ECMWF wind fields without further model input for sources located in a polluted background. NO 2 patterns under calm wind ... ...

Abstract	We present a new method to quantify NO x emissions and corresponding atmospheric lifetimes from OMI NO 2 observations together with ECMWF wind fields without further model input for sources located in a polluted background. NO 2 patterns under calm wind conditions are used as proxy for the spatial patterns of NO x emissions, and the effective atmospheric NO x lifetime is determined from the change of spatial patterns measured at larger wind speeds. Emissions are subsequently derived from the NO 2 mass above the background, integrated around the source of interest. Lifetimes and emissions are estimated for 17 power plants and 53 cities located in non-mountainous regions across China and the USA. The derived lifetimes for the ozone season (May–September) are 3.8 ± 1.0 h (mean ± standard deviation) with a range of 1.8 to 7.5 h. The derived NO x emissions show generally good agreement with bottom-up inventories for power plants and cities. Regional inventory shows better agreement with top-down estimates for Chinese cities compared to global inventory, most likely due to different downscaling approaches adopted in the two inventories.
Keywords	Physics ; QC1-999 ; Chemistry ; QD1-999
Subject code	290
Language	English
Publishing date	2016-04-01T00:00:00Z
Publisher	Copernicus Publications
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Article ; Online: MAX-DOAS measurements of NO 2 , SO 2 , HCHO, and BrO at the Mt. Waliguan WMO GAW global baseline station in the Tibetan Plateau

J. Ma / S. Dörner / S. Donner / J. Jin / S. Cheng / J. Guo / Z. Zhang / J. Wang / P. Liu / G. Zhang / J. Pukite / J. Lampel / T. Wagner

Atmospheric Chemistry and Physics, Vol 20, Pp 6973-

2020 Volume 6990

Abstract: Mt. Waliguan Observatory (WLG) is a World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) global baseline station in China. WLG is located at the northeastern part of the Tibetan Plateau (36 ∘ 17 ′ N, 100 ∘ 54 ′ E, 3816 m a.s.l.) and is ... ...

Abstract	Mt. Waliguan Observatory (WLG) is a World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) global baseline station in China. WLG is located at the northeastern part of the Tibetan Plateau (36 ∘ 17 ′ N, 100 ∘ 54 ′ E, 3816 m a.s.l.) and is representative of the pristine atmosphere over the Eurasian continent. We made long-term ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements at WLG during the period 2012–2015. In this study, we retrieve the differential slant column densities (dSCDs) and estimate the tropospheric background mixing ratios of different trace gases, including NO 2 , SO 2 , HCHO, and BrO, using the measured spectra at WLG. Averaging of 10 original spectra is found to be an “optimum option” for reducing both the statistical error of the spectral retrieval and systematic errors in the analysis. The dSCDs of NO 2 , SO 2 , HCHO, and BrO under clear-sky and low-aerosol-load conditions are extracted from measured spectra at different elevation angles at WLG. By performing radiative transfer simulations with the model TRACY-2, we establish approximate relationships between the trace gas dSCDs at 1 ∘ elevation angle and the corresponding average tropospheric background volume mixing ratios. Mixing ratios of these trace gases in the lower troposphere over WLG are estimated to be in a range of about 7 ppt (January) to 100 ppt (May) for NO 2 , below 0.5 ppb for SO 2 , between 0.4 and 0.9 ppb for HCHO, and lower than 0.3 ppt for BrO. The chemical box model simulations constrained by the NO 2 concentration from our MAX-DOAS measurements show that there is a little net ozone loss ( −0.8 ppb d −1 ) for the free-tropospheric conditions and a little net ozone production (0.3 ppb d −1 ) for the boundary layer conditions over WLG during summertime. Our study provides valuable information and data sets for further investigating tropospheric chemistry in the background atmosphere and its links to anthropogenic activities.
Keywords	Physics ; QC1-999 ; Chemistry ; QD1-999
Subject code	333
Language	English
Publishing date	2020-06-01T00:00:00Z
Publisher	Copernicus Publications
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Article ; Online: Cloud detection and classification based on MAX-DOAS observations

T. Wagner / A. Apituley / S. Beirle / S. Dörner / U. Friess / J. Remmers / R. Shaiganfar

Atmospheric Measurement Techniques, Vol 7, Iss 5, Pp 1289-

2014 Volume 1320

Abstract: Multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations of aerosols and trace gases can be strongly influenced by clouds. Thus, it is important to identify clouds and characterise their properties. In this study we investigate the ...

Abstract	Multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations of aerosols and trace gases can be strongly influenced by clouds. Thus, it is important to identify clouds and characterise their properties. In this study we investigate the effects of clouds on several quantities which can be derived from MAX-DOAS observations, like radiance, the colour index (radiance ratio at two selected wavelengths), the absorption of the oxygen dimer O 4 and the fraction of inelastically scattered light (Ring effect). To identify clouds, these quantities can be either compared to their corresponding clear-sky reference values, or their dependencies on time or viewing direction can be analysed. From the investigation of the temporal variability the influence of clouds can be identified even for individual measurements. Based on our investigations we developed a cloud classification scheme, which can be applied in a flexible way to MAX-DOAS or zenith DOAS observations: in its simplest version, zenith observations of the colour index are used to identify the presence of clouds (or high aerosol load). In more sophisticated versions, other quantities and viewing directions are also considered, which allows subclassifications like, e.g., thin or thick clouds, or fog. We applied our cloud classification scheme to MAX-DOAS observations during the Cabauw intercomparison campaign of Nitrogen Dioxide measuring instruments (CINDI) campaign in the Netherlands in summer 2009 and found very good agreement with sky images taken from the ground and backscatter profiles from a lidar.
Keywords	Meteorology. Climatology ; QC851-999 ; Physics ; QC1-999 ; Science ; Q ; Environmental engineering ; TA170-171 ; Earthwork. Foundations ; TA715-787
Subject code	520
Language	English
Publishing date	2014-05-01T00:00:00Z
Publisher	Copernicus Publications
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Estimating the volcanic emission rate and atmospheric lifetime of SO 2 from space

S. Beirle / C. Hörmann / M. Penning de Vries / S. Dörner / C. Kern / T. Wagner

Atmospheric Chemistry and Physics, Vol 14, Iss 16, Pp 8309-

a case study for Kīlauea volcano, Hawai`i

2014 Volume 8322

Abstract: We present an analysis of SO 2 column densities derived from GOME-2 satellite measurements for the Kīlauea volcano (Hawai`i) for 2007–2012. During a period of enhanced degassing activity in March–November 2008, monthly mean SO 2 emission rates and ... ...

Abstract	We present an analysis of SO 2 column densities derived from GOME-2 satellite measurements for the Kīlauea volcano (Hawai`i) for 2007–2012. During a period of enhanced degassing activity in March–November 2008, monthly mean SO 2 emission rates and effective SO 2 lifetimes are determined simultaneously from the observed downwind plume evolution and meteorological wind fields, without further model input. Kīlauea is particularly suited for quantitative investigations from satellite observations owing to the absence of interfering sources, the clearly defined downwind plumes caused by steady trade winds, and generally low cloud fractions. For March–November 2008, the effective SO 2 lifetime is 1–2 days, and Kīlauea SO 2 emission rates are 9–21 kt day −1 , which is about 3 times higher than initially reported from ground-based monitoring systems.
Keywords	Physics ; QC1-999 ; Chemistry ; QD1-999
Language	English
Publishing date	2014-08-01T00:00:00Z
Publisher	Copernicus Publications
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: MAX-DOAS observations of the total atmospheric water vapour column and comparison with independent observations

T. Wagner / M. O. Andreae / S. Beirle / S. Dörner / K. Mies / R. Shaiganfar

Atmospheric Measurement Techniques, Vol 6, Iss 1, Pp 131-

2013 Volume 149

Abstract: We developed an algorithm for the retrieval of the atmospheric water vapour column from Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations in the yellow and red spectral range. The retrieval is based on the so-called ... ...

Abstract	We developed an algorithm for the retrieval of the atmospheric water vapour column from Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations in the yellow and red spectral range. The retrieval is based on the so-called geometric approximation and does not depend on explicit a priori information for individual observations, extensive radiative transfer simulations, or the construction of large look-up tables. Disturbances of the radiative transfer due to aerosols and clouds are simply corrected using the simultaneously measured absorptions of the oxygen dimer, O 4 . We applied our algorithm to MAX-DOAS observations made at the Max Planck Institute for Chemistry in Mainz, Germany, from March to August 2011, and compared the results to independent observations. Good agreement with Aerosol Robotic Network (AERONET) and European Centre for Medium-Range Weather Forecasting (ECMWF) H 2 O vertical column densities (VCDs) is found, while the agreement with satellite observations is less good, most probably caused by the shielding effect of clouds for the satellite observations. Good agreement is also found with near-surface in situ observations, and it was possible to derive average daily H 2 O scale heights (between 1.5 km and 3 km). MAX-DOAS measurements use cheap and simple instrumentation and can be run automatically. One important advantage of our algorithm is that the H 2 O VCD can be retrieved even under cloudy conditions (except clouds with very high optical thickness).
Keywords	Meteorology. Climatology ; QC851-999 ; Physics ; QC1-999 ; Science ; Q ; DOAJ:Meteorology and Climatology ; DOAJ:Earth and Environmental Sciences ; Environmental engineering ; TA170-171 ; Earthwork. Foundations ; TA715-787
Subject code	520
Language	English
Publishing date	2013-01-01T00:00:00Z
Publisher	Copernicus Publications
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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