Aerosol Optical Properties Based on Ground and Satellite Retrievals during a Serious Haze Episode in December 2015 over Beijing

Abstract

An extreme haze event occurred in the Beijing area from 17 to 23 December 2015. Ground-based measurements and satellite observations during this event were used to further our understanding of the formation process of haze pollution and aerosol optical properties. The results suggest that high relative humidity, poor diffusion conditions (low wind speed and stable stratification) and favorable secondary transformation conditions under the hygroscopic growth of aerosol and high emissions led to this serious haze episode. During the haze period, the daily average value was 1.15 and 0.42 for aerosol optical depth (AOD 500nm ) and columnar water-vapor (CWV, in cm), respectively. On 19 December, the correlation coefficient between CWV and AOD 500nm was 0.91, indicating the effect of hygroscopic growth of fine-mode articles. The daily average values for Ångström exponent, fine-mode fraction, aerosol absorption optical depth, and Ångström absorption exponent were 1.19, 0.81, 0.11 and 1.47, respectively, which suggests that fine aerosol particles were dominant in the atmosphere and fine-mode particles were the dominant contributor to atmospheric extinction during the haze period. Moreover, it also reflects that there were more absorbing aerosol particles during the haze period. Compared with other polluted periods with a bimodal distribution, there was an obvious trimodal distribution on 19 December. There were three peaks at radii of about 0.1 µm, 0.5-0.8 µm and 4 µm. Satellite observations show that there was an obvious aerosol layer in the Beijing area during the haze period, concentrated at ground level to within 2 km in the upper layers. The types of aerosol were mainly composed of mixed pollution aerosols.

Large contribution of meteorological factors to inter-decadal changes in regional aerosol optical depth

“…It is worth noting that, in addition to the increased explained proportion of SO 2 and BC, among these meteorological factors, the role of diffusion-related parameters (such as horizontal and vertical wind speed, representing horizontal and vertical diffusion, respectively) seems to be the most prominent. This is consistent with the findings of Gui et al (2019), who found wind speed to be the dominant meteorological driver for decadal changes in fine particulate matter over SC, based on a 19-year record of satellite-retrieved fine particulate matter data (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016).…”

“…For example, using the long-term and high-quality AOD datasets from the Aerosol Robotic Network (AERONET), found that North America and Europe experienced a uniform decrease in AOD from 2000 to 2013. Che et al (2015) estimated the change in AOD based on AOD data at 12 long-term ground-based sites in China from the China Aerosol Remote Sensing Network (CARSNET) and found that AOD showed a downward trend from 2006 to 2009 and an upward trend from 2009 to 2013. Compared with the spatial sparseness of ground-based observations, inferences from satellite-based sensors can provide a global perspective of AOD change, due to their continuous spatial measurements.…”

Study of Persistent Foggy-Hazy Composite Pollution in Winter over Huainan Through Ground-Based and Satellite Measurements

“…Aerosols are solid particles or suspended liquids in the atmosphere that are the result of natural activities [1,2], burning fuels [3,4], and human activities [5,6]. In recent years, atmospheric aerosols have had a major impact on human health [7], ecosystems [8] and geochemical cycles [9].…”

Changes in Haze Trends in the Sichuan-Chongqing Region, China, 1980 to 2016

“…In recent decades, as a result of a remarkable increase in the emissions of primary pollutants caused by the rapid development of China's economy and urbanization, China has frequently suffered from persistent and severe haze events with high concentration of pollutants, which has aroused considerable concern of the society [1][2][3][4][5]. A high loading (or concentration) of aerosol particles concentration during haze days can reduce visibility through directly scattering and absorbing the incident light, which has potentially impact on road traffic and air transportation [6][7][8]. Furthermore, numerous studies have shown that, as a result of the intensification of air pollution (especially fine particulate matter pollution), some potential health risks have been induced, including respiratory 1c), and unfavorable meteorological conditions.…”