Retrieval and evaluation of tropospheric-aerosol extinction profiles using multi-axis differential optical absorption spectroscopy (MAX-DOAS) measurements over Athens, Greece
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Published:2021-01-29
Issue:1
Volume:14
Page:749-767
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ISSN:1867-8548
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Container-title:Atmospheric Measurement Techniques
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language:en
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Short-container-title:Atmos. Meas. Tech.
Author:
Gratsea Myrto, Bösch TimORCID, Kokkalis Panagiotis, Richter AndreasORCID, Vrekoussis Mihalis, Kazadzis Stelios, Tsekeri Alexandra, Papayannis AlexandrosORCID, Mylonaki MariaORCID, Amiridis VassilisORCID, Mihalopoulos Nikos, Gerasopoulos Evangelos
Abstract
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.
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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