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

Abstract

Abstract. We estimated the distribution of aerosol optical thickness (AOT) with a spatial resolution of 1 km over the Moscow megacity using the MAIAC aerosol product based on MODIS satellite data (Lyapustin et al., 2018) for the warm period of the year (May–September, 2001–2017). AERONET (Aerosol Robotic Network)-based validation of satellite estimates near the city centre at Moscow_MSU_MO and over the Moscow suburbs at Zvenigorod revealed that MAIAC AOT at 0.47 µm 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 the MAIAC algorithm effectively removed the effect of the bright urban surface in the city centre. For the ground-based measurements, the difference between annual median AOT at Moscow_MO_MSU and Zvenigorod (ΔAOT) varied within −0.002 to +0.03, with statistically significant positive bias for most years, and an average ΔAOT was about 0.02. According to the MAIAC dataset, the 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 in pollutant emissions in Moscow, which is mainly caused by the environmental regulations. According to the MAIAC dataset, the most pronounced spatial AOT differences over the territory of Moscow were observed at the 5 % quantile level, where they reached 0.05–0.06 over several locations and could be attributed to the stationary sources of aerosol pollution, for example, large areas of construction sites, aerosol pollution from roads and highways, or agriculture activities. The differences between the maximum and the mean AOT for different quantiles, except the 95 % quantile, within the Moscow region, were 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 “New” Moscow territory which experienced an intensive build-up and agricultural development.

Columnar and surface urban aerosol in Moscow megacity according to measurements and simulations with COSMO-ART model

“…We showed that the columnar aerosol characteristics during the 420 intensive spring campaigns on the whole are close to those during the warm period of the year. However, AODs are slightly smaller compared with the average values for these months over the 2001-2020 period, which is in the agreement with the observed negative AOD trend in Moscow megacity (Zhdanova et a., 2020, Chubarova et al, 2016. A reduction in fine mode AOD fraction may be associated with a decrease in the emissions of urban aerosol precursor gases in recent years (Zhdanova et al, 2020).…”

“…The April-May period of 2018-2019 is 225 characterized by slightly lower AOD500, which is in an agreement with a negative AOD500 trend in Moscow in recent years (Zhdanova et al,2020;Chubarova et al, 2016). The lower fraction of fine mode aerosol (64% compared to 71-73%) may also indicate the decrease in the formation of secondary aerosol due to the effective reduction of urban gas precursor emissions in Moscow (Zhdanova et al, 2020). However, in general, the aerosol conditions in April and May of 2018-2019 correspond to those during warm period with a slightly reduced AOD500 and its fine mode fraction, which corresponds to the observed 230 trends of purification of the Moscow atmosphere in recent years.…”

“…The summer AOD500 maximum is associated with the active formation of submicron aerosol with fine mode AOD500 fraction higher 80%. The April-May period of 2018-2019 is 225 characterized by slightly lower AOD500, which is in an agreement with a negative AOD500 trend in Moscow in recent years (Zhdanova et al,2020;Chubarova et al, 2016). The lower fraction of fine mode aerosol (64% compared to 71-73%) may also indicate the decrease in the formation of secondary aerosol due to the effective reduction of urban gas precursor emissions in Moscow (Zhdanova et al, 2020).…”

Overview: Recent advances on the understanding of the Northern Eurasian environments and of the urban air quality in China - Pan Eurasian Experiment (PEEX) program perspective

“…In the complex situation of the plurality of emissions, an important research task remains in the Moscow megacity environment for the assessment of the air quality and potential sources through aerosol composition analyses. Moscow aerosol pollution has been studied using a special AeroRadCity-2018 experiment (Chubarova et al, 2019) and satellite data with the application of new MAIAC/MODIS aerosol algorithm with a 1-km resolution (Zhdanova et al, 2020). An advanced source apportionment for this environment was performed using combined Fourier-transform infrared spectroscopy data and statistical principal component analysis (Popovicheva et al, 2020b).…”

Spatiotemporal Variations of Aerosol Optical Depth in the Atmosphere over Baikal Region Based on MODIS Data

“…The main and most studied optical characteristic of aerosols is the aerosol optical depth (AOD) of the atmosphere. Many authors [1][2][3][4][5][6][7] have analyzed the interannual variations and seasonal variability of different parameters of the atmospheric transparency over Russia. In [4], the results of long-term studies (1995-2017) of the physical properties and chemical composition of atmospheric aerosols in the Baikal region in three sites are considered.…”