Assessment of urban aerosol pollution over Moscow megacity by MAIAC aerosol product

• Main Authors: Zhdanova, Ekaterina Y., Chubarova, Natalia Y., Lyapustin, Alexei I.
• Format: Text
• Language: English
• Published: 2019
• Subjects: Aerosol Robotic Network
• Online Access: https://doi.org/10.5194/amt-2019-325; https://www.atmos-meas-tech-discuss.net/amt-2019-325/

We estimated the distribution of aerosol optical thickness (AOT) with a spatial resolution of 1 km over Moscow megacity using MAIAC aerosol product based on MODIS satellite data (Lyapustin et al., 2018) for the warm period of year (May–September). AERONET (Aerosol Robotic Network)-based validation near the city centre at Moscow_MSU_MO and over Moscow suburbs at Zvenigorod revealed that MAIAC AOT at 470 nm is in agreement with AERONET AOT though underestimated by 0.05–0.1 for AOT < 1 and overestimated for smoke conditions with AOT > 1. The MAIAC AOT biases were almost the same for the Moscow_MSU_MO and Zvenigorod AERONET sites, which indicated that MAIAC effectively removed the effect of the bright urban surface in the city centre. For the ground-based measurements, the annual median AOT difference between Moscow_MO_MSU and Zvenigorod (ΔAOT) varied within −0.002±0.03 with statistically significant positive bias for most years and an average ΔAOT of ~ 0.02. According to MAIAC dataset, ΔAOT varied within ±0.01 and was not statistically significant. The ΔAOT started decreasing recently due to intensive urban development of the territory around Zvenigorod and the decrease of pollutant emissions in Moscow, which is mainly caused by the environmental regulations. According to the MAIAC dataset, the most pronounced spatial AOT difference over the territory of Moscow was observed at 5 % quantile level, where it reached 0.05–0.06 over several locations and could be attributed to the stationary sources of aerosol pollution, for example, power plants, or aerosol pollution from roads. The difference between the maximum and the mean AOT for different quantiles, except the 95 % quantile, within the Moscow region, was about 0.02–0.04 which could be attributed to the local aerosol sources. The application of the MAIAC algorithm over the whole Moscow region has revealed a decreasing AOT trend over the centre of Moscow and an increasing trend over the <q>New</q> Moscow territory which experienced an intensive build-up and agricultural development in the north and the south parts of this district, respectively.