scholarly journals Retrieval and evaluation of tropospheric aerosol extinction profiles using MAX-DOAS measurements over Athens, Greece

2020 ◽  
Author(s):  
Myrto Gratsea ◽  
Tim Bösch ◽  
Panos Kokkalis ◽  
Andreas Richter ◽  
Mihalis Vrekoussis ◽  
...  
Keyword(s):  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Aerosol Extinction ◽  
The Sun ◽  
Tropospheric Aerosol ◽  
Lidar Measurements ◽  
Vertical Distributions ◽  
Term Basis ◽  
Photometric Measurements ◽  
First Time

Abstract. In this study, we report on the retrieval of aerosol extinction profiles from ground-based scattered sunlight multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements, carried out at Athens, Greece. It is the first time that aerosol profiles are retrieved from MAX-DOAS measurements in Athens. The reported aerosol vertical distributions at 477 nm are derived from the oxygen dimer (O4) differential slant column density observations at different elevation angles by applying the BOREAS retrieval algorithm. Four case studies have been selected for validation purposes; the retrieved aerosol profiles and the corresponding aerosol optical depths (AODs) from the MAX-DOAS are compared with lidar extinction profiles and with sun photometric measurements (AERONET observations), respectively. Despite the different approach of each method regarding the retrieval of the aerosol information, the comparison with the lidar measurements at 532 nm reveals a very good agreement in terms of vertical distribution, with r > 0.85 in all cases. The AODs from the MAX-DOAS and the sun-photometer (the latter at 500 nm) show a satisfactory correlation (with r ≈ 0.6 in three out of the four cases). The comparison indicates that the MAX-DOAS systematically underestimates the AOD in the cases of large particles (small Ångström exponent) and for measurements at small relative azimuthal angles between the viewing direction and the Sun. Better agreement is achieved in the morning, at large relative azimuthal angles. Overall, the aerosol profiles retrieved from MAX-DOAS measurements are of good quality; thus, new perspectives are opened up for assessing urban aerosol pollution on a long term-basis in Athens from continuous and uninterrupted MAX-DOAS measurements.

scholarly journals Retrieval and evaluation of tropospheric-aerosol extinction profiles using multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements over Athens, Greece

2021 ◽  
Vol 14 (1) ◽  
pp. 749-767
Author(s):  
Myrto Gratsea ◽  
Tim Bösch ◽  
Panagiotis Kokkalis ◽  
Andreas Richter ◽  
Mihalis Vrekoussis ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Optimal Estimation ◽  
Differential Optical Absorption Spectroscopy ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Aerosol Extinction ◽  
The Sun ◽  
Tropospheric Aerosol ◽  
Vertical Distributions

Abstract. In this study, we report on the retrieval of aerosol extinction profiles from ground-based scattered sunlight multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements, carried out at Athens, Greece. It is the first time that aerosol profiles are retrieved from MAX-DOAS measurements in Athens. The reported aerosol vertical distributions at 477 nm are derived from the oxygen dimer (O4) differential-slant-column-density observations at different elevation angles by applying the BRemen Optimal estimation REtrieval for Aerosol and trace gaseS (BOREAS) retrieval algorithm. Four case studies have been selected for validation purposes; the retrieved aerosol profiles and the corresponding aerosol optical depths (AODs) from the MAX-DOAS are compared with lidar extinction profiles and with sun-photometric measurements (Aerosol Robotic Network, AERONET, observations), respectively. Despite the different approach of each method regarding the retrieval of the aerosol information, the comparison with the lidar measurements at 532 nm reveals a very good agreement in terms of vertical distribution, with r>0.90 in all cases. The AODs from the MAX-DOAS and the sun photometer (the latter at 500 nm) show a satisfactory correlation (with 0.45 < r < 0.7 in three out of the four cases). The comparison indicates that the MAX-DOAS systematically underestimates the AOD in the cases of large particles (small Ångström exponent) and for measurements at small relative azimuthal angles between the viewing direction and the sun. Better agreement is achieved in the morning, at large relative azimuthal angles. Overall, the aerosol profiles retrieved from MAX-DOAS measurements are of good quality; thus, new perspectives are opened up for assessing urban aerosol pollution on a long-term basis in Athens from continuous and uninterrupted MAX-DOAS measurements.

scholarly journals The global 3-D distribution of tropospheric aerosols as characterized by CALIOP

2013 ◽  
Vol 13 (6) ◽  
pp. 3345-3361 ◽  
Author(s):  
D. M. Winker ◽  
J. L. Tackett ◽  
B. J. Getzewich ◽  
Z. Liu ◽  
M. A. Vaughan ◽  
...  
Keyword(s):  
Lower Troposphere ◽  
Aerosol Extinction ◽  
Transport Pathways ◽  
3 Dimensional ◽  
Clear Sky ◽  
Tropospheric Aerosol ◽  
Vertical Distributions ◽  
Dimensional Distribution ◽  
Level 3 ◽  
Sky Conditions

Abstract. The CALIOP lidar, carried on the CALIPSO satellite, has been acquiring global atmospheric profiles since June 2006. This dataset now offers the opportunity to characterize the global 3-D distribution of aerosol as well as seasonal and interannual variations, and confront aerosol models with observations in a way that has not been possible before. With that goal in mind, a monthly global gridded dataset of daytime and nighttime aerosol extinction profiles has been constructed, available as a Level 3 aerosol product. Averaged aerosol profiles for cloud-free and all-sky conditions are reported separately. This 6-yr dataset characterizes the global 3-dimensional distribution of tropospheric aerosol. Vertical distributions are seen to vary with season, as both source strengths and transport mechanisms vary. In most regions, clear-sky and all-sky mean aerosol profiles are found to be quite similar, implying a lack of correlation between high semi-transparent cloud and aerosol in the lower troposphere. An initial evaluation of the accuracy of the aerosol extinction profiles is presented. Detection limitations and the representivity of aerosol profiles in the upper troposphere are of particular concern. While results are preliminary, we present evidence that the monthly-mean CALIOP aerosol profiles provide quantitative characterization of elevated aerosol layers in major transport pathways. Aerosol extinction in the free troposphere in clean conditions, where the true aerosol extinction is typically 0.001 km−1 or less, is generally underestimated, however. The work described here forms an initial global 3-D aerosol climatology which we plan to extend and improve over time.

scholarly journals Observations of the summertime atmospheric pollutants vertical distributions and the corresponding ozone production in Shanghai, China

2017 ◽  
Author(s):  
Chengzhi Xing ◽  
Cheng Liu ◽  
Shanshan Wang ◽  
Ka Lok Chan ◽  
Yang Gao ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Pearson Correlation ◽  
A Priori ◽  
Lower Troposphere ◽  
Sensitivity Study ◽  
Atmospheric Pollutants ◽  
Ozone Production ◽  
Optical Absorption Spectroscopy ◽  
Lidar Measurements ◽  
Vertical Distributions

Abstract. Ground based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) and lidar measurements were performed in Shanghai, China during May 2016 to investigate the summertime atmospheric pollutants vertical distribution. In this study, vertical profiles of aerosol extinction coefficient, nitrogen dioxide (NO2) and formaldehyde (HCHO) concentrations were retrieved from MAX-DOAS measurement using the Heidelberg Profile (HeiPro) algorithm, while vertical distribution of ozone (O3) was obtained from an ozone lidar. Sensitivity study of the MAX-DOAS aerosol profile retrieval shows that the a priori aerosol profile shape has significant influences on the aerosol profile retrieval. Aerosol profiles retrieved from MAX-DOAS measurements with Gaussian a priori demonstrate the best agreements with simultaneous lidar measurements and vehicle-based tethered-balloon observations among all a priori aerosol profiles. MAX-DOAS measured tropospheric NO2Vertical Column Densities (VCDs) show a good agreement with OMI satellite observations with Pearson correlation coefficient (R) of 0.95. In addition, measurements of the O3 vertical distribution indicate that the ozone productions do not only occur at surface level but also at higher altitudes (about 1.1 km). Planetary boundary layer (PBL) height, horizontal and vertical wind fields information were integrated to discuss the ozone formation at upper altitudes. The results reveal that enhanced ozone concentrations at ground and upper altitudes are not directly related to horizontal and vertical transportations. Similar patterns of O3 and HCHO vertical distributions were observed during this campaign, which implies that the ozone productions near to the surface and at higher altitudes are mainly influenced by the abundance of volatile organic compounds (VOCs) in the lower troposphere.

scholarly journals Airborne DOAS measurements in Arctic: vertical distributions of aerosol extinction coefficient and NO<sub>2</sub> concentration

2011 ◽  
Vol 11 (5) ◽  
pp. 13525-13574
Author(s):  
A. Merlaud ◽  
M. Van Roozendael ◽  
N. Theys ◽  
C. Fayt ◽  
C. Hermans ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Marine Boundary Layer ◽  
Scattered Light ◽  
Optical Absorption Spectroscopy ◽  
North Coast ◽  
Aerosol Extinction ◽  
Back Trajectories ◽  
The North ◽  
Source Regions ◽  
Vertical Distributions

Abstract. We report airborne differential optical absorption spectroscopy (DOAS) measurements of aerosol extinction and NO2 tropospheric profiles performed off the North coast of Norway in April 2008. The DOAS instrument was installed on the Safire ATR-42 aircraft during the POLARCAT-France spring campaign and recorded scattered light spectra in near-limb geometry using a scanning telescope. We use O4 slant column measurements to derive the aerosol extinction at 360 nm. Regularization is based on the maximum a posteriori solution, for which we compare a linear and a logarithmic approach. The latter inherently constrains the solution to positive values and yields aerosol extinction profiles more consistent with independently measured size distributions. Two soundings are presented, performed on 8 April 2008 above 71° N, 22° E and on 9 April 2008 above 70° N, 17.8° E. The first profile shows aerosol extinction and NO2 in the marine boundary layer with respective values of 0.04±0.005 km−1 and 1.9±0.3 × 109 molec cm−3. A second extinction layer of 0.01±0.003 km−1 is found at 4 km altitude. During the second sounding, clouds prevented us to retrieve profile parts under 3 km altitude but a layer with enhanced extinction (0.025±0.005 km−1) and NO2 (1.95±0.2 × 109 molec cm−3) is clearly detected at 4 km altitude. From CO and ozone in-situ measurements complemented by back-trajectories, we interpret the measurements in the free troposphere as, for the first sounding, a mix between stratospheric and polluted air from Northern Europe and for the second sounding, polluted air from Central Europe containing NO2. Considering the boundary layer measurements of the first flight, modeled source regions indicate closer sources, especially the Kola Peninsula smelters, which can explain the NO2 enhancement not correlated with a CO increase at the same altitude.

scholarly journals MAX-DOAS retrieval of aerosol extinction properties in Madrid, Spain

2016 ◽  
Author(s):  
Shanshan Wang ◽  
Carlos A. Cuevas ◽  
Udo Frieß ◽  
Alfonso Saiz-Lopez
Keyword(s):  
Saharan Dust ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Back Trajectory ◽  
Aerosol Extinction ◽  
Inversion Algorithm ◽  
Back Trajectory Analysis ◽  
Particle Layer ◽  
Level Of Agreement

Abstract. Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were performed in the urban environment of Madrid, Spain, from March to September in 2015. The O4 absorption in the UV was used to retrieve the aerosol extinction profile by an inversion algorithm. The results show a good agreement between the hourly retrieved aerosol optical depth (AOD) and the correlative Aerosol Robotic Network (AERONET) product, with a correlation coefficient of R = 0.87. Higher AODs are found in the summer season due to the more frequent occurrence of Saharan dust intrusions. The surface aerosol extinction coefficient as retrieved by the MAX-DOAS measurements was also compared to in situ PM2.5 concentrations. The level of agreement between both measurements indicates that the MAX-DOAS retrieval has the ability to characterize the extinction by particle near the surface. The retrieval algorithm was also used to study a case of severe dust intrusion on 12 May 2015. The capability of the MAX-DOAS retrieval to recognize the dust event including an elevated particle layer is investigated along with air mass back trajectory analysis.

scholarly journals MAX-DOAS retrieval of aerosol extinction properties in Madrid, Spain

2016 ◽  
Vol 9 (10) ◽  
pp. 5089-5101 ◽  
Author(s):  
Shanshan Wang ◽  
Carlos A. Cuevas ◽  
Udo Frieß ◽  
Alfonso Saiz-Lopez
Keyword(s):  
Saharan Dust ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Back Trajectory ◽  
Aerosol Extinction ◽  
Inversion Algorithm ◽  
Back Trajectory Analysis ◽  
Particle Layer ◽  
Level Of Agreement

Abstract. Multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements were performed in the urban environment of Madrid, Spain, from March to September 2015. The O4 absorption in the ultraviolet (UV) spectral region was used to retrieve the aerosol extinction profile using an inversion algorithm. The results show a good agreement between the hourly retrieved aerosol optical depth (AOD) and the correlative Aerosol Robotic Network (AERONET) product, with a correlation coefficient of R =  0.87. Higher AODs are found in the summer season due to the more frequent occurrence of Saharan dust intrusions. The surface aerosol extinction coefficient as retrieved by the MAX-DOAS measurements was also compared to in situ PM2.5 concentrations. The level of agreement between both measurements indicates that the MAX-DOAS retrieval has the ability to characterize the extinction of aerosol particles near the surface. The retrieval algorithm was also used to study a case of severe dust intrusion on 12 May 2015. The capability of the MAX-DOAS retrieval to recognize the dust event including an elevated particle layer is investigated along with air mass back-trajectory analysis.

scholarly journals Multiple wavelength retrieval of tropospheric aerosol optical properties from MAXDOAS measurements in Beijing

2010 ◽  
Vol 3 (4) ◽  
pp. 863-878 ◽  
Author(s):  
K. Clémer ◽  
M. Van Roozendael ◽  
C. Fayt ◽  
F. Hendrick ◽  
C. Hermans ◽  
...  
Keyword(s):  
Real Time ◽  
Optimal Estimation ◽  
Retrieval Algorithm ◽  
Aerosol Extinction ◽  
Vertical Profiles ◽  
Atmospheric Conditions ◽  
Multiple Wavelength ◽  
Tropospheric Aerosol ◽  
Wide Range ◽  
On Line

Abstract. We report on the retrieval of aerosol extinction profiles at four wavelengths from ground-based multi-axis differential absorption spectroscopy (MAXDOAS) measurements performed in Beijing, China. Measurements were made over a 10-month time period (June 2008 to April 2009) using a newly developed MAXDOAS instrument. A retrieval algorithm, based on an on-line implementation of the radiative transfer code LIDORT and the optimal estimation technique, has been designed to provide near real time information on aerosol extinction vertical profiles. The algorithm was applied to O4 measurements at four wavelengths (360, 477, 577, and 630 nm). The total aerosol optical depths (AODs) calculated from the retrieved profiles exhibit higher values in spring and summer and lower values in autumn and winter. Comparison of the retrieved total AODs with values from a co-located CIMEL sunphotometer revealed a good correlation. The best results are obtained for the UV region with a correlation coefficient (R) of 0.91 and a slope of the linear regression fit of 1.1. At the longest wavelength, R drops down to 0.67 and the slope increases to 1.5. The results confirm that good quality O4 slant column measurements are essential for the success of the retrievals. A method is presented to determine a correction factor to account for systematic errors. It is demonstrated that the algorithm is capable of reliably retrieving aerosol extinction profiles for a wide range of atmospheric conditions (total AODs at 360 nm ranging from about 0.1 to 3). The results open up new perspectives for the extension of the algorithm for the near real time retrieval of trace gas vertical profiles.

scholarly journals Eight-component retrievals from ground-based MAX-DOAS observations

2011 ◽  
Vol 4 (6) ◽  
pp. 1027-1044 ◽  
Author(s):  
H. Irie ◽  
H. Takashima ◽  
Y. Kanaya ◽  
K. F. Boersma ◽  
L. Gast ◽  
...  
Keyword(s):  
Transport Model ◽  
Satellite Observations ◽  
Optical Absorption Spectroscopy ◽  
Retrieval Algorithm ◽  
Measuring Instruments ◽  
Data Sets ◽  
Aerosol Extinction ◽  
Chemical Transport Model ◽  
Model Calculations ◽  
Mean Values

Abstract. We attempt for the first time to retrieve lower-tropospheric vertical profile information for 8 quantities from ground-based Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) observations. The components retrieved are the aerosol extinction coefficients at two wavelengths, 357 and 476 nm, and NO2, HCHO, CHOCHO, H2O, SO2, and O3 volume mixing ratios. A Japanese MAX-DOAS profile retrieval algorithm, version 1 (JM1), is applied to observations performed at Cabauw, the Netherlands (51.97° N, 4.93° E), in June–July 2009 during the Cabauw Intercomparison campaign of Nitrogen Dioxide measuring Instruments (CINDI). Of the retrieved profiles, we focus here on the lowest-layer data (mean values at altitudes 0–1 km), where the sensitivity is usually highest owing to the longest light path. In support of the capability of the multi-component retrievals, we find reasonable overall agreement with independent data sets, including a regional chemical transport model (CHIMERE) and in situ observations performed near the surface (2–3 m) and at the 200-m height level of the tall tower in Cabauw. Plumes of enhanced HCHO and SO2 were likely affected by biogenic and ship emissions, respectively, and an improvement in their emission strengths is suggested for better agreement between CHIMERE simulations and MAX-DOAS observations. Analysis of air mass factors indicates that the horizontal spatial representativeness of MAX-DOAS observations is about 3–15 km (depending mainly on aerosol extinction), comparable to or better than the spatial resolution of current UV-visible satellite observations and model calculations. These demonstrate that MAX-DOAS provides multi-component data useful for the evaluation of satellite observations and model calculations and can play an important role in bridging different data sets having different spatial resolutions.

scholarly journals The global 3-D distribution of tropospheric aerosols as characterized by CALIOP

2012 ◽  
Vol 12 (9) ◽  
pp. 24847-24893 ◽  
Author(s):  
D. M. Winker ◽  
J. L. Tackett ◽  
B. J. Getzewich ◽  
Z. Liu ◽  
M. A. Vaughan ◽  
...  
Keyword(s):  
Lower Troposphere ◽  
Aerosol Extinction ◽  
Upper Troposphere ◽  
3 Dimensional ◽  
Clear Sky ◽  
Tropospheric Aerosol ◽  
Vertical Distributions ◽  
Dimensional Distribution ◽  
Sky Conditions ◽  
Seasonal And Interannual Variations

Abstract. The CALIOP lidar, carried on the CALIPSO satellite, has been acquiring global atmospheric profiles since June 2006. This dataset now offers the opportunity to characterize the global 3-D distribution of aerosol as well as seasonal and interannual variations, and confront aerosol models with observations in a way that has not been possible before. With that goal in mind, a monthly global gridded dataset of daytime and nighttime aerosol extinction profiles has been constructed. Averaged aerosol profiles for cloud-free and all-sky conditions are reported separately. This 6-yr dataset characterizes the global 3-dimensional distribution of tropospheric aerosol. Vertical distributions are seen to vary with season, as both source strengths and transport mechanisms vary. In most regions, clear-sky and all-sky mean aerosol profiles are found to be quite similar, implying a lack of correlation between high semi-transparent cloud and aerosol in the lower troposphere. An initial evaluation of the accuracy of the aerosol extinction profiles is presented. Detection limitations and the representivity of aerosol profiles in the upper troposphere are of particular concern. While results are preliminary, we present evidence that the monthly-mean gridded CALIOP aerosol profiles are representative for aerosol extinction greater than about 0.001 km−1 and up to an altitude of 4–6 km in most cases. The work described here forms an initial global 3-D aerosol climatology which hopefully will be extended and improved over time.

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