The Impact of the Aerosol Direct Radiative Forcing on Deep Convection and Air Quality in the Pearl River Delta Region

Abstract

Literature has reported the remarkable aerosol impact on low-level cloud by direct radiative forcing (DRF). Impacts on middle-upper troposphere cloud are not yet fully understood, even though this knowledge is important for regions with a large spatial heterogeneity of emissions and aerosol concentration. We assess the aerosol DRF and its cloud response in June (with strong convection) in Pearl River Delta region for 2008-2012 at cloud-resolving scale using an air quality-climate coupled model. Aerosols suppress deep convection by increasing atmospheric stability leading to less evaporation from the ground. The relative humidity is reduced in middle-upper troposphere due to induced reduction in both evaporation from the ground and upward motion. The cloud reduction offsets 20% of the aerosol DRF. The weaker vertical mixing further increases surface aerosol concentration by up to 2.90 μg/m 3 . These findings indicate the aerosol DRF impact on deep convection and in turn regional air quality.Plain Language Summary Aerosol may affect regional climate and in turn air quality. While previous research has focused on the aerosol impact on low-level cloud, the impact on middle-upper troposphere needs to be further understood. This study aims to assess the impact of the aerosol direct radiative forcing (DRF) on deep convection and air quality in the Pearl River Delta region where it has a large spatial heterogeneity of emissions and aerosol concentration. We use an air quality-climate coupled model to simulate the aerosol DRF and its cloud response in June (with strong convection) in Pearl River Delta region for 2008-2012. Aerosols suppress deep convection by increasing atmospheric stability leading to less evaporation from the ground. The relative humidity is reduced in middle-upper troposphere due to induced reduction in evaporation from both the ground and upward motion. The cloud reduction offsets 20% of the aerosol DRF. The weaker vertical mixing further increases surface aerosol concentration by up to 2.90 μg/m 3 . Our findings are anticipated to provide important information for regional climate and air-quality forecast.

Assessing the formation and evolution mechanisms of severe haze pollution in Beijing−Tianjin−Hebei region by using process analysis

“…Anthropogenic activities associated with rapidly developed industrialization and urbanization have been leading to a sustained increase in the amounts of atmospheric pollutants, especially in the fast-developing countries (IPCC, 2013). As one of the largest emission sources of aerosols and their precursors, China has been suffering from serious air pollution for years (Lei et al, 2011;Li et al, 2011), with severe haze events frequently occurring in winter, especially over large urban agglomerations, such as the North China Plain (NCP) (Han et al, 2014;Gao et al, 2015), the Yangtze River Delta area (YRD) (Ding et al, 2016;Wang et al, 2016a), the Pearl River Delta area (PRD) (Fan et al, 2015;Liu et al, 2018b), and the Sichuan Basin (SCB) (Zhao et al, 2018;Zhang et al, 2019). During severe haze events, the observed maximum hourly surface-layer PM 2.5 (fine particulate matter with aerodynamic diameter of 2.5 µm or less) concentration exceeded 1000 µg m -3 (Wang et al, 2013b;Sun et al, 2016;Li et al, 2017a), which could significantly influence visibility (Li et al, 2014), radiation budget (Steiner et al, 2013), atmospheric circulation (Jiang et al, 2017), cloud properties (Unger et al, 2009), and even human health (Guo et al, 2017).…”

The Trend Reversal of Dust Aerosol Over East Asia and the North Pacific Ocean Attributed to Large‐Scale Meteorology, Deposition, and Soil Moisture

“…The deserts in the arid and semiarid regions of northwestern China, including the Taklamakan Desert and the Gobi Desert, are some of the largest dust sources in the Eurasian continent (Ding et al, 2005). Dust aerosols not only scatter solar radiation directly but also modify the microphysical properties of clouds and precipitation through indirect radiative effects (Ge et al, 2011;Z. Liu, Yim, et al, 2018;Su et al, 2008;Zhao et al, 2010Zhao et al, , 2011, thereby influencing global weather and the climate system Huang et al, 2006;Li et al, 2016;R.…”

Influence of Black Carbon Aerosol on the Atmospheric Instability

“…Recent studies reveal that the heating efficiency of absorbing aerosol is more in the upper boundary layer compared to lower boundary layer height (Ding et al, ; Wang et al, ). It has been shown by earlier researchers that absorbing aerosols below clouds may increase cloud cover by destabilizing the planetary boundary layer and, on the other hand, it is also probable that it reduces cloud cover by reducing surface fluxes (Feingold et al, ; Liu et al, ). Several studies on aerosols in the last two decades reveal that absorbing aerosols may cause to decrease the atmospheric convective processes (Fan et al, ; Rosenfeld, ; Rosenfeld et al, ).…”