scholarly journals Simultaneous observations by sky radiometer and MAX-DOAS for characterization of biomass burning plumes in central Thailand in January–April 2016

2018 ◽  
Author(s):  
Hitoshi Irie ◽  
Hossain Mohammed Syedul Hoque ◽  
Alessandro Damiani ◽  
Hiroshi Okamoto ◽  
Al Mashroor Fatmi ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Surface Concentration ◽  
Wavelength Dependence ◽  
Optical Absorption Spectroscopy ◽  
Near Surface ◽  
Aerosol Absorption ◽  
Volatile Organic Carbon ◽  
Carbon Aerosols ◽  
Central Thailand

Abstract. The first intensive multi-component ground-based remote sensing observations by sky radiometer and Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) were performed simultaneously at the SKYNET/Phimai site located in central Thailand (15.18° N, 102.56° E) from January to April 2016. The period corresponds to the dry season associated with the intense biomass burning (BB) activity around the site. The near-surface concentration of formaldehyde (HCHO) retrieved from MAX-DOAS was found to be a useful tracer for BB plumes. As the HCHO concentration tripled from 3 to 9 ppbv, the ratio of gaseous glyoxal to HCHO concentrations in daytime decreased from ~ 0.04 to ~ 0.03, responding presumably to the increased contribution of volatile organic carbon emissions from BB. In addition, clear increases in aerosol absorption optical depths (AAODs) retrieved from sky radiometer observations were seen with the HCHO enhancement. At a HCHO of 9 ppbv, AAOD at a wavelength of 340 nm reached as high as ~ 0.15 ± 0.03. The wavelength dependence of AAODs at 340–870 nm was quantified by the absorption Ångström exponent (AAE), providing evidence for the presence of brown carbon aerosols at an AAE of 1.5 ± 0.2. Thus, our multi-component observations around central Thailand are expected to provide unique constraints for understanding physical/chemical/optical properties of BB plumes.

scholarly journals Simultaneous observations by sky radiometer and MAX-DOAS for characterization of biomass burning plumes in central Thailand in January–April 2016

2019 ◽  
Vol 12 (1) ◽  
pp. 599-606 ◽  
Author(s):  
Hitoshi Irie ◽  
Hossain Mohammed Syedul Hoque ◽  
Alessandro Damiani ◽  
Hiroshi Okamoto ◽  
Al Mashroor Fatmi ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Surface Concentration ◽  
Wavelength Dependence ◽  
Optical Absorption Spectroscopy ◽  
Near Surface ◽  
Aerosol Absorption ◽  
Volatile Organic Compound Emissions ◽  
Carbon Aerosols ◽  
Central Thailand

Abstract. The first intensive multicomponent ground-based remote-sensing observations by sky radiometer and multi-axis differential optical absorption spectroscopy (MAX-DOAS) were performed simultaneously at the SKYNET Phimai site located in central Thailand (15.18∘ N, 102.56∘ E) from January to April 2016. The period corresponds to the dry season associated with intense biomass burning (BB) activity around the site. The near-surface concentration of formaldehyde (HCHO) retrieved from MAX-DOAS was found to be a useful tracer for absorption aerosols from BB plumes, when BB was the dominant source of HCHO and absorption aerosols over other sources. As the HCHO concentration tripled from 3 to 9 ppbv, the ratio of gaseous glyoxal to HCHO concentrations in daytime decreased from ∼0.04 to ∼0.03, responding presumably to the increased contribution of volatile organic compound emissions from BB. In addition, clear increases in aerosol absorption optical depths (AAODs) retrieved from sky radiometer observations were seen with the HCHO enhancement. At a HCHO of 9 ppbv, AAOD at a wavelength of 340 nm reached as high as ∼0.15±0.03. The wavelength dependence of AAODs at 340–870 nm was quantified by the absorption Ångström exponent (AAE), providing evidence for the presence of brown carbon aerosols at an AAE of 1.5±0.2. Thus, our multicomponent observations around central Thailand are expected to provide unique constraints for understanding physical–chemical–optical properties of BB plumes.

scholarly journals Satellite-based evidence of wavelength-dependent aerosol absorption in biomass burning smoke inferred from ozone monitoring instrument

2011 ◽  
Vol 11 (3) ◽  
pp. 7291-7319 ◽  
Author(s):  
H. Jethva ◽  
O. Torres
Keyword(s):  
Biomass Burning ◽  
Spectral Dependence ◽  
Central Africa ◽  
Wavelength Dependence ◽  
Carbonaceous Aerosol ◽  
Ozone Monitoring Instrument ◽  
Aerosol Model ◽  
Monitoring Instrument ◽  
Aerosol Absorption ◽  
Ozone Monitoring

Abstract. We provide satellite-based evidence of the spectral dependence of absorption in biomass burning aerosols over South America using near-UV measurements made by Ozone Monitoring Instrument (OMI) during 2005–2007. Currently, OMAERUV aerosol algorithm characterizes carbonaceous aerosol as "gray" aerosol, meaning no wavelength dependence in aerosol absorption. With this assumption, OMI-derived aerosol optical depth (AOD) is found to be over-estimated significantly compared to that of AERONET at several sites during intense biomass burning events (August–September). The assumption on height of aerosols and other parameters seem to be reasonable and unable to explain large discrepancy in the retrieval. The specific ground-based studies have revealed strong spectral dependence in aerosol absorption in the near-UV region that indicates the presence of organic carbon. A new set of OMI aerosol retrieval with assumed wavelength-dependent aerosol absorption in the near-UV region (Absorption Angstrom Exponent λ−2.5 to −3.0) provided much improved retrieval of AOD with significantly reduced bias. Also, the new retrieval of single-scattering albedo is in better agreement with those of AERONET within the uncertainties (Δω=±0.03). The new smoke aerosol model was also found to be valid over the biomass burning region of central Africa and northern India. Together with suggesting vast improvement in the retrieval of aerosol properties from OMI, present study demonstrates the near-UV capabilities of OMI in separating aerosols containing organics from pure black carbon through OMI-AERONET integrated measurements.

scholarly journals Four years of ground-based MAX-DOAS observations of HONO and NO<sub>2</sub> in the Beijing area

2013 ◽  
Vol 13 (4) ◽  
pp. 10621-10660 ◽  
Author(s):  
F. Hendrick ◽  
J.-F. Müller ◽  
K. Clémer ◽  
M. De Mazière ◽  
C. Fayt ◽  
...  
Keyword(s):  
Seasonal Cycle ◽  
Surface Concentration ◽  
Early Morning ◽  
Optical Absorption Spectroscopy ◽  
Oh Radicals ◽  
Beijing City ◽  
City Center ◽  
Data Set ◽  
Near Surface ◽  
Local Noon

Abstract. Ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of nitrous acid (HONO) and its precursor NO2 (nitrogen dioxide) have been performed daily in Beijing city center (39.98° N, 116.38° E) from July 2008 to April 2009 and at the suburban site of Xianghe (39.75° N, 116.96° E) located ~ 60 km east of Beijing from March 2010 to December 2012. This extensive data set allowed for the first time the investigation of the seasonal cycle of HONO as well as its diurnal variation in and in the vicinity of a megacity. Our study was focused on the HONO and NO2 near-surface concentrations (0–200 m layer) and total vertical column densities (VCDs) retrieved by applying the Optimal Estimation Method to the MAX-DOAS observations. Monthly averaged HONO near-surface concentrations at local noon display a strong seasonal cycle with a maximum in late fall/winter (~ 0.8 and 0.7 ppb at Beijing and Xianghe, respectively) and a minimum in summer (~ 0.1 ppb at Beijing and 0.03 ppb at Xianghe). The seasonal cycles of HONO and NO2 appear to be highly correlated, with correlation coefficients in the 0.7–0.9 and 0.5–0.8 ranges at Beijing and Xianghe, respectively. The stronger correlation of HONO with NO2 and also with aerosols observed in Beijing suggests possibly larger role of NO2 conversion into HONO in the Beijing city center than at Xianghe. The observed diurnal cycle of HONO near-surface concentration shows a maximum in the early morning (about 1 ppb at both sites) likely resulting from night-time accumulation, followed by a decrease to values of about 0.1–0.4 ppb around local noon. The HONO/NO2 ratio shows a similar pattern with a maximum in the early morning (values up to 0.08) and a decrease to ~ 0.01–0.02 around local noon. The seasonal and diurnal cycles of the HONO near-surface concentration are found to be similar in shape and in relative amplitude to the corresponding cycles of the HONO total VCD and are therefore likely mainly driven by the balance between HONO sources and the photolytic sink, whereas dilution effects appear to play only a minor role. The estimation of OH radical production from HONO and O3 photolysis based on retrieved HONO near-surface concentrations and calculated photolysis rates indicate that HONO is by far the largest source of OH radicals in winter as well as in the early morning at all seasons, while the contribution of O3 dominates in summer from mid-morning until mid-afternoon.

scholarly journals Photoacoustic and nephelometric spectroscopy of aerosol optical properties with a supercontinuum light source

2013 ◽  
Vol 6 (12) ◽  
pp. 3501-3513 ◽  
Author(s):  
N. Sharma ◽  
I. J. Arnold ◽  
H. Moosmüller ◽  
W. P. Arnott ◽  
C. Mazzoleni
Keyword(s):  
Optical Properties ◽  
Light Source ◽  
Wavelength Dependence ◽  
Common Salt ◽  
Design Development ◽  
Aerosol Optical Properties ◽  
Scattering Coefficients ◽  
Aerosol Absorption ◽  
Multi Wavelength

Abstract. A novel multi-wavelength photoacoustic-nephelometer spectrometer (SC-PNS) has been developed for the optical characterization of atmospheric aerosol particles. This instrument integrates a white light supercontinuum laser with photoacoustic and nephelometric spectroscopy to measure aerosol absorption and scattering coefficients at five wavelength bands (centered at 417, 475, 542, 607, and 675 nm). These wavelength bands are selected from the continuous spectrum of the laser (ranging from 400–2200 nm) using a set of optical interference filters. Absorption and scattering measurements on laboratory-generated aerosol samples were performed sequentially at each wavelength band. To test the instrument we measured the wavelength dependence of absorption and scattering coefficients of kerosene soot and common salt aerosols. Results were favorably compared to those obtained with a commercial 3-wavelength photoacoustic and nephelometer instrument demonstrating the utility of the SC light source for studies of aerosol optical properties at selected wavelengths. Here, we discuss instrument design, development, calibration, performance and experimental results.

scholarly journals Horizontal distribution of tropospheric NO<sub>2</sub> and aerosols derived by dual-scan multi-wavelength MAX-DOAS measurements in Uccle, Belgium

2021 ◽  
Author(s):  
Ermioni Dimitropoulou ◽  
Francois Hendrick ◽  
Martina Michaela Friedrich ◽  
Frederik Tack ◽  
Gaia Pinardi ◽  
...  
Keyword(s):  
A Priori ◽  
Elevation Angle ◽  
Optimal Estimation ◽  
Horizontal Distribution ◽  
Optical Absorption Spectroscopy ◽  
Azimuthal Direction ◽  
Vertical Column ◽  
Near Surface ◽  
Multi Wavelength

Abstract. Dual-scan ground-based Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of tropospheric nitrogen dioxide (NO2) and aerosols have been carried out in Uccle (50.8° N, 4.35° E; Brussels region, Belgium) for two years, from March 2018 to February 2020. The MAX-DOAS instrument has been operating in both UV and Visible wavelength ranges in a dual-scan configuration consisting of two sub-modes: (1) an elevation scan in a fixed viewing azimuthal direction and (2) an azimuthal scan in a fixed low elevation angle (2°). By analyzing the O4 and NO2 dSCDs at six different wavelength intervals along every azimuthal direction and by applying a new Optimal-Estimation-based inversion approach, the horizontal distribution of the NO2 near-surface concentrations and vertical column densities (VCDs) and the aerosols near-surface extinction coefficient are retrieved along ten azimuthal directions. The retrieved horizontal NO2 concentration profiles allow the identification of the main NO2 hotspots in the Brussels area. Correlative comparisons of the retrieved horizontal NO2 distribution have been conducted with airborne, mobile, and satellite datasets, and overall a good agreement is found. The comparison with TROPOMI observations reveals that the characterization of the horizontal distribution of tropospheric NO2 VCDs by ground-based measurements, the appropriate sampling of TROPOMI pixels, and an adequate a priori NO2 profile shape in TROPOMI retrievals lead to a better consistency between satellite and ground-based datasets.

scholarly journals Intercomparison of aerosol extinction profiles retrieved from MAX-DOAS measurements

2016 ◽  
Author(s):  
U. Frieß ◽  
H. Klein Baltink ◽  
S. Beirle ◽  
K. Clèmer ◽  
F. Hendrick ◽  
...  
Keyword(s):  
Optimal Estimation ◽  
Optical Absorption Spectroscopy ◽  
Measuring Instruments ◽  
Aerosol Extinction ◽  
Vertical Profiles ◽  
Near Surface ◽  
Aerosol Absorption ◽  
Sun Photometer ◽  
Absorption Measurements

Abstract. A first direct intercomparison of aerosol vertical profiles from Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations, performed during the Cabauw Intercomparison Campaign of Nitrogen Dioxide measuring Instruments (CINDI) in summer 2009, is presented. Five out of 14 participants of the CINDI campaign reported aerosol extinction profiles and aerosol optical thickness (AOT) as deduced from observations of differential slant column densities of the oxygen collision complex (O4) at different elevation angles. Aerosol vertical profiles and AOT are compared to backscatter profiles from a ceilometer instrument and to sun photometer measurements, respectively. Furthermore, the near-surface aerosol extinction coefficient is compared to in-situ measurements of a humidity controlled nephelometer and dry aerosol absorption measurements. The participants of this intercomparison exercise use different approaches for the retrieval of aerosol information, including the retrieval of the full vertical profile using optimal estimation and a parametrised approach with a prescribed profile shape. Despite these large conceptual differences, and also differences in the wavelength of the observed O4 absorption band, good agreement in terms of the vertical structure of aerosols within the boundary layer is achieved between the aerosol extinction profiles retrieved by the different groups and the backscatter profiles observed by the ceilometer instrument. AOT from MAX-DOAS and sun photometer show a good correlation (R > 0.8), but all participants systematically underestimate the AOT. Substantial differences between the near-surface aerosol extinction from MAX-DOAS and from the humidified nephelometer remain largely unresolved.

scholarly journals Intercomparison of aerosol extinction profiles retrieved from MAX-DOAS measurements

2016 ◽  
Vol 9 (7) ◽  
pp. 3205-3222 ◽  
Author(s):  
U. Frieß ◽  
H. Klein Baltink ◽  
S. Beirle ◽  
K. Clémer ◽  
F. Hendrick ◽  
...  
Keyword(s):  
Optimal Estimation ◽  
Optical Absorption Spectroscopy ◽  
Measuring Instruments ◽  
Aerosol Extinction ◽  
Vertical Profiles ◽  
Near Surface ◽  
Aerosol Absorption ◽  
Sun Photometer ◽  
Absorption Measurements

Abstract. A first direct intercomparison of aerosol vertical profiles from Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations, performed during the Cabauw Intercomparison Campaign of Nitrogen Dioxide measuring Instruments (CINDI) in summer 2009, is presented. Five out of 14 participants of the CINDI campaign reported aerosol extinction profiles and aerosol optical thickness (AOT) as deduced from observations of differential slant column densities of the oxygen collision complex (O4) at different elevation angles. Aerosol extinction vertical profiles and AOT are compared to backscatter profiles from a ceilometer instrument and to sun photometer measurements, respectively. Furthermore, the near-surface aerosol extinction coefficient is compared to in situ measurements of a humidity-controlled nephelometer and dry aerosol absorption measurements. The participants of this intercomparison exercise use different approaches for the retrieval of aerosol information, including the retrieval of the full vertical profile using optimal estimation and a parametrised approach with a prescribed profile shape. Despite these large conceptual differences, and also differences in the wavelength of the observed O4 absorption band, good agreement in terms of the vertical structure of aerosols within the boundary layer is achieved between the aerosol extinction profiles retrieved by the different groups and the backscatter profiles observed by the ceilometer instrument. AOTs from MAX-DOAS and sun photometer show a good correlation (R>0.8), but all participants systematically underestimate the AOT. Substantial differences between the near-surface aerosol extinction from MAX-DOAS and from the humidified nephelometer remain largely unresolved.

scholarly journals Photoacoustic and nephelometric spectroscopy of aerosol optical properties with a supercontinuum light source

2013 ◽  
Vol 6 (4) ◽  
pp. 6293-6327 ◽  
Author(s):  
N. Sharma ◽  
I. J. Arnold ◽  
H. Moosmüller ◽  
W. P. Arnott ◽  
C. Mazzoleni
Keyword(s):  
Optical Properties ◽  
Light Source ◽  
Wavelength Dependence ◽  
Common Salt ◽  
Design Development ◽  
Aerosol Optical Properties ◽  
Scattering Coefficients ◽  
Aerosol Absorption ◽  
Multi Wavelength

Abstract. A novel multi-wavelength photoacoustic-nephelometer spectrometer (SC-PNS) has been developed for the optical characterization of atmospheric aerosol particles. This instrument integrates a white light supercontinuum laser with photoacoustic and nephelometric spectroscopy to measure aerosol absorption and scattering coefficients at five wavelength bands (centered at 417, 475, 542, 607, and 675 nm). These wavelength bands were selected from the continuous spectrum of the laser (ranging from 400–2200 nm) using a set of optical interference filters. Absorption and scattering measurements on laboratory-generated aerosol samples were performed sequentially at each wavelength band. To test the instrument we measured the wavelength dependence of absorption and scattering coefficients of kerosene soot and common salt aerosols. Results were favorably compared to those obtained with a commercial 3-wavelength photoacoustic and nephelometer instrument demonstrating the utility of the SC light source for studies of aerosol optical properties at selected wavelengths. Here, we discuss instrument design, development, calibration, performance and experimental results.

scholarly journals Four years of ground-based MAX-DOAS observations of HONO and NO<sub>2</sub> in the Beijing area

2014 ◽  
Vol 14 (2) ◽  
pp. 765-781 ◽  
Author(s):  
F. Hendrick ◽  
J.-F. Müller ◽  
K. Clémer ◽  
P. Wang ◽  
M. De Mazière ◽  
...  
Keyword(s):  
Seasonal Cycle ◽  
Estimation Method ◽  
Surface Concentration ◽  
Early Morning ◽  
City Centre ◽  
Optical Absorption Spectroscopy ◽  
Oh Radicals ◽  
Beijing City ◽  
Near Surface ◽  
Local Noon

Abstract. Ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements of nitrous acid (HONO) and its precursor NO2 (nitrogen dioxide) as well as aerosols have been performed daily in Beijing city centre (39.98° N, 116.38° E) from July 2008 to April 2009 and at the suburban site of Xianghe (39.75° N, 116.96° E) located ~60 km east of Beijing from March 2010 to December 2012. This extensive dataset allowed for the first time the investigation of the seasonal cycle of HONO as well as its diurnal variation in and in the vicinity of a megacity. Our study was focused on the HONO and NO2 near-surface concentrations (0–200 m layer) and total vertical column densities (VCDs) and also aerosol optical depths (AODs) and extinction coefficients retrieved by applying the Optimal Estimation Method to the MAX-DOAS observations. Monthly averaged HONO near-surface concentrations at local noon display a strong seasonal cycle with a maximum in late fall/winter (~0.8 and 0.7 ppb at Beijing and Xianghe, respectively) and a minimum in summer (~0.1 ppb at Beijing and 0.03 ppb at Xianghe). The seasonal cycles of HONO and NO2 appear to be highly correlated, with correlation coefficients in the 0.7–0.9 and 0.5–0.8 ranges at Beijing and Xianghe, respectively. The stronger correlation of HONO with NO2 and also with aerosols observed in Beijing suggests possibly larger role of NO2 conversion into HONO in the Beijing city center than at Xianghe. The observed diurnal cycle of HONO near-surface concentration shows a maximum in the early morning (about 1 ppb at both sites) likely resulting from night-time accumulation, followed by a decrease to values of about 0.1–0.4 ppb around local noon. The HONO / NO2 ratio shows a similar pattern with a maximum in the early morning (values up to 0.08) and a decrease to ~0.01–0.02 around local noon. The seasonal and diurnal cycles of the HONO near-surface concentration are found to be similar in shape and in relative amplitude to the corresponding cycles of the HONO total VCD and are therefore likely driven mainly by the balance between HONO sources and the photolytic sink, whereas dilution effects appear to play only a minor role. The estimation of OH radical production from HONO and O3 photolysis based on retrieved HONO near-surface concentrations and calculated photolysis rates indicate that in the 0–200 m altitude range, HONO is by far the largest source of OH radicals in winter as well as in the early morning at all seasons, while the contribution of O3 dominates in summer from mid-morning until mid-afternoon.

Comparison of Ion-Milling Techniques For Cross-Sectional TEM of Semiconductors

1985 ◽  
Vol 43 ◽  
pp. 166-167
Author(s):  
Julia T. Luck ◽  
C. W. Boggs ◽  
S. J. Pennycook
Keyword(s):  
Analytical Techniques ◽  
Sample Surface ◽  
Ion Milling ◽  
Cross Sectional ◽  
Reliable Technique ◽  
Near Surface ◽  
Transmission Electron ◽  
Thin Region ◽  
Transient Thermal

The use of cross-sectional Transmission Electron Microscopy (TEM) has become invaluable for the characterization of the near-surface regions of semiconductors following ion-implantation and/or transient thermal processing. A fast and reliable technique is required which produces a large thin region while preserving the original sample surface. New analytical techniques, particularly the direct imaging of dopant distributions, also require good thickness uniformity. Two methods of ion milling are commonly used, and are compared below. The older method involves milling with a single gun from each side in turn, whereas a newer method uses two guns to mill from both sides simultaneously.

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