Abstract
In recent years, large-area heavy haze pollution cases occur frequently in eastern China, especially evident in Beijing-Tianjin-Hebei and the surrounding regions. In order to operationally monitor the process of larger regional heavy haze events, a type of quantitative method based on satellite remote sensing and numerical simulations was first established and applied in multiple heavy haze processes in the research area. First, this study proposed the operational haze aerosol optical depth (HOD) method by combining Terra, Aqua satellite and WRF-NAQPM numerical simulation in haze days. Second, based on the coupled HOD data, we proposed the quantitative method for obtaining the process and severity degree for larger regional heavy haze events. Finally, this study used the method applying it to several typical heavy pollution events which occurred in Beijing-Tianjin-Hebei and its three surrounding provinces in the winter season from 1 November 2015 to 4 January 2016. The validation for HOD retrieval results showed that the couple HOD from this study have good accuracy, the linear correlation coefficient between retrieval HOD and the AERONET Beijing station data reached over 0.8, and the linear correlation coefficient between the retrieval HOD and the regional ground monitoring station PM2.5 data reached over 0.7. The applied results showed that the method in this study is feasible to reflect the whole process of heavy haze events. Analysis of the typical heavy haze pollution events showed that the set of quantitative haze judging method in this study was consistent with the meteorological conditions in haze days also verifying that the method for haze inversion and the process analysis is reliable.
Highlights
Beijing-Tianjin-Hebei and the surrounding provinces are the regions with the heaviest haze pollution in eastern China which seriously influences the air quality and poses hard threats to the physical health of the public, drawing extensive attention domestic and overseas [1,2]
Analysis of the typical heavy haze pollution events showed that the set of quantitative haze judging method in this study was consistent with the meteorological conditions in haze days verifying that the method for haze inversion and the process analysis is reliable
The method mainly relies on haze aerosol optical depth (HOD) retrieved from satellite retrieval in non-cloudy areas, when some areas are covered by clouds, use the PM2.5 data from numerical simulations method to obtain HOD to fill in, so the HOD data of the whole area can be got
Summary
Beijing-Tianjin-Hebei and the surrounding provinces are the regions with the heaviest haze pollution in eastern China which seriously influences the air quality and poses hard threats to the physical health of the public, drawing extensive attention domestic and overseas [1,2]. Air Pollution Prevention and Control Action Plan promulgated by the State Council in September 2013 [3,4]. The so-called grey-haze [5,6], is defined by the World Meteorological Organization in meteorological phenomena as large amounts of tiny dry particles suspended in the air, which are hardly visible for the naked eye, and make the sky become turbid, causing the visibility to drop down to 5 km or even lower [7]. The large amounts of tiny dry particles are often composed of fine particulate. Atmosphere 2017, 8, 222 matter PM2.5 (PM with diameters ≤ 2.5 μm), which is an index of one of the major pollutants as stipulated in the ambient air quality standard (AAQS) of China [8]. The haze is essentially a kind of atmospheric pollution phenomenon caused mainly by fine particulate matter [9,10,11,12,13,14], the haze and heavy haze pollution process is mainly the fine particulate matters pollution process, and the monitoring of haze process is the monitoring of the fine particulate matters pollution process.
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