A new method to determine the aerosol optical properties from multiple-wavelength O<sub>4</sub> absorptions by MAX-DOAS observation

Abstract

Ground-based multi-axis differential optical absorption spectroscopy (MAX-DOAS) observation was carried out from November 2016 to February 2017 in Beijing, China, to measure the O 4 absorptions in UV and visible bands and further to illustrate its relationship with aerosol optical properties (AOPs) under different weather types. According to relative humidity, visibility, and PM 2.5 , we classified the observation periods into clear, light-haze, haze, heavy-haze, fog, and rainy weather conditions. There are obvious differences for measured AOPs under different weather conditions, especially scattering coefficient (σ sca ) and absorption coefficient (σ sca ). It was also found that both the O 4 differential slant column densities (DSCDs) at the UV and visible bands varied in the order of clear days > lighthaze days > haze days > heavy-haze days > fog days. The correlation coefficients (R 2 ) between O 4 DSCDs at 360.8 and 477.1 nm mainly varied in the order of clear days > light-haze days > haze days > heavy-haze days. Based on the statistics of O 4 DSCDs at an elevation angle 1 • with the corresponding linear regression between UV and visible bands of segmental periods, the relationships between O 4 DSCDs and AOPs were established. It should mainly be clear or light-haze days when the correlation slope is greater than 1.0, with a correlation coefficient (R 2 ) greater than 0.9, and O 4 DSCDs mainly greater than 2.5 × 10 43 molec. cm −2 . Meanwhile, σ sca and σ abs are less than 45 and 12 Mm −1 , respectively. For haze or heavy-haze days, the correlation slope is less than 0.6, with an R 2 less than 0.8, and O 4 DSCDs mainly less than 1.3 × 10 43 molec. cm −2 , under which σ sca and σ abs are mainly located at 200-900 and 20-60 Mm −1 . Additionally, the determination method was well validated based on another MAX-DOAS measurement at Gucheng from 19 to 27 November 2016. For more precise and accurate inversion of AOPs, more detailed look-up tables for O 4 multiple-wavelength absorptions need to be developed. Since the ground surface AOPs were determined using MAX-DOAS observation at a 1 • elevation in this study, we hope to highlight the potential of retrieved vertical spatially resolved AOPs being expected when multiple elevation angles of MAX-DOAS observation are used together.Published by Copernicus Publications on behalf of the European Geosciences Union.

Elevated dust layers inhibit dissipation of heavy anthropogenic surface air pollution

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Improved Anthropogenic SO2 Retrieval from High-Spatial-Resolution Satellite and its Application during the COVID-19 Pandemic

“…Although, due to different instruments and retrieval algorithms, there are some biases between different products. , After removing local biases, the corrected SO 2 observations from different satellites show similar values . Compared with conventional ground-based measurements, satellite remote sensing can measure tropospheric pollutants in a larger area. − We can use products measured by a satellite to estimate SO 2 emissions, track the SO 2 transmission, and evaluate the efficiency of emission reduction policies. , Satellite products can also identify the source of SO 2 emissions and fill gaps in the existing inventories . The combination of satellite-based emissions and conventional inventories improves the consistency of observations and models …”

“…13,14 After removing local biases, the corrected SO 2 observations from different satellites show similar values. 14 Compared with conventional ground-based measurements, 15 satellite remote sensing can measure tropospheric pollutants in a larger area. 16−19 We can use products measured by a satellite to estimate SO 2 emissions, track the SO 2 transmission, and evaluate the efficiency of emission reduction policies.…”

Observations by Ground-Based MAX-DOAS of the Vertical Characters of Winter Pollution and the Influencing Factors of HONO Generation in Shanghai, China

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