Reversal of Aerosol Properties in Eastern China with Rapid Decline of Anthropogenic Emissions

Abstract

The clean air actions of the Chinese government since 2013 have led to rapid reduction in anthropogenic emissions during the last five years. In this study, we present a regional-scale insight into the transition of aerosol properties during this special period based on integrated Moderate Resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging Spectroradiometer (MISR), and ground-based AERONET (AErosol RObotic NETwork) observations. As a response, aerosols in eastern China have exhibited notable reversal in both the amount and optical properties. Regional haze pollution with Aerosol Optical Depth (AOD) > 1.0 in northern China declined from more than ~80 days per year to less than ~30 days. While fine-mode particles exhibited a continuous decrease by ~30-40% during the time period of 2013–2018, the levels of coarse aerosols had no regular variations. MISR fraction AOD of different size modes shows that there has been an obvious overall decline in coarse particles over eastern China, but natural sources such as long-range dust transport make a considerable contribution. The Single Scattering Albedo (SSA) increased steadily from 2001 to 2012 by more than ~0.05. In contrast, aerosol absorption has been getting stronger since 2013, with SSA increasing by ~0.03, due to a much larger reduction in sulfate and nitrate. The drastic transition of aerosol properties has greatly changed aerosol radiative forcing (ARF) in eastern China. The negative ARF at the top (TOA) and bottom (BOA) of the atmosphere decreased by ~30 and ~50 W/m2, respectively, in Beijing during the 2001–2012 period. Although aerosol loading continued to decline after 2013, the magnitudes of TOA and BOA ARF have increased by ~10 and ~30 W/m2, respectively, since 2013, due largely to the enhanced aerosol absorption. Our results suggest that more comprehensive observations are needed to improve understanding of the intense climate and environment effects of dramatic aerosol properties in eastern China.

Changes in Clear‐Sky Shortwave Aerosol Direct Radiative Effects Since 2002

“…Since climatological sources of aerosols are used in nondust conditions, any trends in aerosol absorption would not be accounted for in MATCH. This could lead to significant overestimations/underestimations in ADRE trends in regions with large changes in aerosol absorption (Tao et al., 2020).…”

Unmasking the Effects of Aerosols on Greenhouse Warming Over Europe

“…The concentrations of aerosols are in many regions in Asia at the same level or even higher today compared to what the most polluted countries in Europe experienced in the 1980s. Even so, anthropogenic aerosols have started to decline in China during the latest decade (Tao et al., 2020).…”

Long-Term (2005–2017) View of Atmospheric Pollutants in Central China Using Multiple Satellite Observations

“…Other than SO 2 and NO x emissions, trace gases such as ammonia (NH 3 ) and formaldehyde (HCHO) also have important contribution to air pollution in central China. Although satellite products of HCHO and NH 3 are available, their accuracy is much lower compared with NO 2 and SO 2 [27,35]. Despite much smaller variations in emissions than sulfate and nitrate [4], the long-term changes of other major components in PM 2.5 including OC and mineral dust have to be considered in central China.…”

“…However, it should be noted that regional AOD exceeds 0.8 for about more than one quarter of the days during 2005-2014. After the clean air actions taken by the Chinese government in 2013, there has been a rapid decline in particle pollution in eastern China [35]. While there has been a continuous decrease in SO 2 and particle pollutants in central China, the notable increase in NO x indicates a transition from air pollution, i.e., a larger fraction of OC and enhanced O 3 pollution.…”