Abstract
The effects of meteorological changes on particulate matter with a diameter of 10 microns or less (PM10, referred to as PM in this study) and aerosol optical depth (AOD) in Seoul were investigated using observational and modeling analysis. AOD satellite data were used, obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS), and PM concentration data were used from in-situ observations. The Modern-Era Retrospective Analysis for Research and Applications (MERRA) and MERRA Version 2 (MERRA-2) were used for meteorological field analysis in modeling and observation data. The results from this investigation show that meteorological effects on PM and AOD were strong in the month of June, revealing a clear decreasing trend in recent decades. The investigation focused on the underlying mechanisms influencing the reduction in PM resulting from meteorological changes during the months of June. The results of this study reveal that decreases in atmospheric stability and humidity induced the aerosol change observed in recent decades. The changes in atmospheric stability and humidity are highly correlated with changes in the intensity of the East Asian summer monsoon (EASM). This suggests that the unstable and drying atmosphere by weakening of the EASM in recent decades has improved PM air quality in Seoul during the summer. The effects of atmospheric stability and humidity were also observed to vary depending on the aerosol species. Humidity only affects hydrophilic aerosols such as sulfate, nitrate, and ammonium, whereas atmospheric stability affects all species of aerosols, including carbonaceous aerosols.
Highlights
Particulate matter with a diameter of 10 microns or less (PM10, referred to as PM in this study) is a representative indicator of air pollution that is known to affect human respiratory health [1] and cause lung cancer [2]
We found that decreasing trends of air temperature gradient index (ATGI) and humidity index (HI) are much smaller than those of the Modern-Era Retrospective Analysis for Research and Applications (MERRA)-2 reanalysis data for 2003–2017, similar to that of PM
We found that that positively correlated all species, including secondary inorganic aerosols waswas positively correlated withwith all species, including both both secondary inorganic aerosols (SIA; (SIA; sulfate, nitrate, ammonium aerosols) and organic aerosols, include organic and black sulfate, nitrate, and and ammonium aerosols) and organic aerosols, whichwhich include organic and black carbon
Summary
Particulate matter with a diameter of 10 microns or less (PM10 , referred to as PM in this study) is a representative indicator of air pollution that is known to affect human respiratory health [1] and cause lung cancer [2]. Few studies have investigated the effect of the East Asian summer monsoon (EASM) on the PM level in East Asia and suggested that strong EASM decreases aerosol concentration in eastern China through precipitation and wind change [35,36,37,38]. These studies focus on the relation between EASM and PM, but not on the long-term changes in PM owing to variations in meteorological fields. In this study, we investigate the long-term variation of the meteorological effect on aerosol concentration in the Seoul Metropolitan Area during the month of June, when AOD is highest, using station observations, satellite data, reanalysis dataset, and model simulation results
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