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AbstractIn this study, particulate matter (PM) variation has been analyzed to address the dearth of scientific research on air pollution in a coastal city from south India. Mean PM2.5 and PM10 concentrations were 61.6 ± 26.4 and 87.3 ± 35.4 μg/m3. The highest (lowest) seasonal concentration was observed during winter (monsoon). Increase in PM from September to February is attributed to low relative humidity, biomass burning in nearby paddy fields, and continental air mass from the east and north-easterly direction. The mean PM2.5/PM10 ratio was 0.71, with the seasonal ratio ranging between 0.64 (summer) and 0.76 (monsoon), indicating the dominance of anthropogenic PM fraction. PM exhibited typical characteristic of the urban region, i.e., a two-peak diurnal trend during all seasons except monsoon. PM10 (PM2.5) concentrations decreased by ∼7–24.2% (∼11–21%) on the weekends, with the highest reduction in winter seasons. Regarding correlation analysis among PM, CO, and ozone; a negative correlation between PM10 and O3 and a positive correlation between PM and CO was observed. Wind speed and PM10 showed a positive quadratic linear, whereas wind speed and PM2.5 showed a negative linear relationship. The primary sources of particulate matter in Kannur town are motor vehicle emissions, dust from construction work in surrounding zones, and nearby industrial units. [ABSTRACT FROM AUTHOR]

Given the advantages of remote sensing, an increasing number of satellite aerosol optical depths (AOD) have been utilized to evaluate near-ground PM2.5. However, the spatiotemporal relationship between AODs and PM2.5 still lacks a comprehensive investigation, especially in some regions with severe pollution within China. Here, we investigated the spatiotemporal relationships between several satellite AODs and the near-surface PM2.5 concentration across China and its 14 representative regions during 2016–2018 using the correlation coefficient (R), the PM2.5/AOD ratio (η), the geo-detector (q), and the different aerosol-dominated regimes. The results showed that the MODIS AOD from the Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm strongly correlates with PM2.5 (R > 0.6) in China, particularly in the Chengyu (CY), Beijing-Tianjin-Hebei (BTH), and Yangtze River Delta (YRD) regions. The close correlations (R = 0.7) exist between PM2.5 and MODIS and VIIRS AOD from the deep blue (DB) algorithm in the CY, BTH, and YRD regions. Under the key aerosols affecting China (e.g., sulfate and dust), there is a strong correlation (R > 0.5) between the PM2.5 and MODIS and VIIRS AODs from the MAIAC and DB algorithms, with the higher concentration of ground-level PM2.5 per unit of these AODs (η > 130). The MAIAC AOD (Terra/Aqua) can better explain the spatial distribution (q > 0.4) of PM2.5 than those of AODs from the dark target (DT) and DB algorithms applied to the MODIS over China and its specific regions across seasons. The performance of the Advanced Himawari Imager (AHI) AOD (R > 0.5, q > 0.3) was close to that of the MAIAC AOD during the spring and summer; however, it was far less than the MAIAC AOD in the autumn and winter seasons. The investigation provides instructions for estimating the near-surface PM2.5 concentration based on AOD in different regions of China. [ABSTRACT FROM AUTHOR]

High-Mountain Asia (HMA) is a global hotspot of stratospheric intrusion, and elevated surface ozone were observed at ground monitoring sites. Still, links between the variability of surface ozone and stratospheric intrusion at regional scale remain unclear. This study synthesized ground measurements of surface ozone over the HMA and analyzed their seasonal variations. The monthly mean surface ozone concentrations peaked earlier in the south in April and later in the north in July over the HMA. The migration of monthly surface ozone peaks was coupled with the synchronous movement of tropopause folding and westerly jet that created a conducive conditions for stratospheric ozone intrusion. Such intrusion contributed ~65% of surface ozone at three typical sites across the HMA. We demonstrated that surface ozone over the HMA is mainly controlled by stratospheric intrusion, which warrants a proper consideration in understanding atmospheric chemistry and impacts of ozone over this highland region and beyond. [ABSTRACT FROM AUTHOR]

The Pan-Third Pole (PTP) owns complex geography and demographic features where aerosol roles and their impact cannot be neglected as it jeopardizes both the environment and human health. Therefore, we analyzed spatio-temporal aerosol concentration, the influence of meteorological conditions, and underlying aerosol transport mechanisms over the PTP by leveraging observation, satellite dataset, and model outputs. The observation and model simulation result showed that aerosol concentrations exceeded the world health organization (WHO) and China guideline values in most of the locations. This study revealed distinctive seasonality with the highest and lowest aerosol concentrations during the winter and summer seasons, respectively, which could be favored by meteorological conditions and emissions from biomass burning. In response to higher aerosol concentrations, the maximum aerosol optical depth (AOD) values were observed over the major hotspot regions however, interestingly summer high (AOD > 0.8) was observed over the Indo Gangetic Plain (IGP) in South Asia. The columnar aerosol profile indicated that the higher aerosol concentrations were limited within 1-2 km elevation over the densely populated regions over South Asia and Eastern China. However, the significant aerosols concentrations found to be extended as high as 10 km could potentially be driven by the deep convection process and summer monsoon activities. Regionally, the integrated aerosol transport (IAT) for black carbon (BC) and organic carbon (OC) was found to be maximum over SA. Noticeable OC IAT anomaly (~5 times > annual mean) found during spring that was linked with the biomass burning events. Yet, the dust transportation was found to be originated from the arid land and deserts that prolonged especially during summer followed by spring seasons. This study highlights the driver mechanism in aerosol seasonality, transport mechanism, and further motivates the additional assessment into potential dynamic relation between aerosol species, aerosol atmospheric river, and its societal impact. [ABSTRACT FROM AUTHOR]