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Similarities and Differences in the Temporal Variability of PM2.5 and AOD Between Urban and Rural Stations in Beijing.
- Source :
- Remote Sensing; Apr2020, Vol. 12 Issue 7, p1193, 1p
- Publication Year :
- 2020
-
Abstract
- Surface particulate matter with an aerodynamic diameter of <2.5 μm (PM<subscript>2.5</subscript>) and column-integrated aerosol optical depth (AOD) exhibits substantial diurnal, daily, and yearly variabilities that are regionally dependent. The diversity of these temporal variabilities in urban and rural areas may imply the inherent mechanisms. A novel time-series analysis tool developed by Facebook, Prophet, is used to investigate the holiday, seasonal, and inter-annual patterns of PM<subscript>2.5</subscript> and AOD at a rural station (RU) and an urban station (UR) in Beijing. PM<subscript>2.5</subscript> shows a coherent decreasing tendency at both stations during 2014–2018, consistent with the implementation of the air pollution action plan at the end of 2013. RU is characterized by similar seasonal variations of AOD and PM<subscript>2.5</subscript>, with the lowest values in winter and the highest in summer, which is opposite that at UR with maximum AOD, but minimum PM<subscript>2.5</subscript> in summer and minimum AOD, but maximum PM<subscript>2.5</subscript> in winter. During the National Day holiday (1–7 October), both AOD and PM<subscript>2.5</subscript> holiday components regularly shift from negative to positive departures, and the turning point generally occurs on October 4. AODs at both stations steadily increase throughout the daytime, which is most striking in winter. A morning rush hour peak of PM<subscript>2.5</subscript> (7:00–9:00 local standard time (LST)) and a second peak at night (23:00 LST) are observed at UR. PM<subscript>2.5</subscript> at RU often reaches minima (maxima) at around 12:00 LST (19:00 LST), about four hours later (earlier) than UR. The ratio of PM<subscript>2.5</subscript> to AOD (η) shows a decreasing tendency at both stations in the last four years, indicating a profound impact of the air quality control program. η at RU always begins to increase about 1–2 h earlier than that at UR during the daytime. Large spatial and temporal variations of η suggest that caution should be observed in the estimation of PM<subscript>2.5</subscript> from AOD. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 20724292
- Volume :
- 12
- Issue :
- 7
- Database :
- Complementary Index
- Journal :
- Remote Sensing
- Publication Type :
- Academic Journal
- Accession number :
- 142836081
- Full Text :
- https://doi.org/10.3390/rs12071193