Effects of aerosol on downward diffuse radiation under blowing dust and haze conditions.

Aerosols are not only an important component of the atmosphere, but also an indispensable medium for the generation of diffuse radiation (DR) in the atmosphere. This study analyzed the variation of diffuse radiation using ground-based observation under clear sky conditions at Wuhan, and quantifies the effects of aerosol optical and microphysical properties on diffuse radiation under blowing dust and haze conditions. The results are as follows: DR showed a decreasing trend from 2010 to 2014, and an increasing trend with rate of 4.076 W m-2 year−1 from 2014 to 2018. From 2011 to 2016, the diffuse radiation fraction (DRF) showed a trend of first decreasing and then increasing. During the study period, the relationship between aerosol optical depth (AOD) and DRF showed a significant and solid relationship with an R2 of 0.874. DR increased from 159.592 W m−2 in clean air to 195.420 W m−2 during the haze period, and AOD also increased from 0.607 in clean air to 0.914 during the haze period, which demonstrated the increase in diffuse radiation with the increase in aerosol loading. During the haze period, the sensitivity of fine-mode aerosol effective particle size (REFFF) and asymmetry (ASY) to DR was higher, with determination coefficients of 0.541 and 0.317, respectively, which were attributed to the hygroscopic growth of the aerosol resulting in larger particle size, increased ASY, and scattering of more solar radiation. The absorption properties of aerosols affect the DR during blowing dust, with a coefficient of determination between single scattering albedo (SSA) and DR of 0.40. The aerosol diffuse radiation effect (ADRE) was 111.688 W m−2 during the clean air period, ADRE increased by 31.839, 13.312 W m−2 during the haze and blowing dust periods, respectively, compared to that during the clean air period. The study of aerosols and radiation under different pollution conditions helps to understand the mechanisms behind local climate change and pollution phenomena, and deepens our understanding of the impact of pollution on the environment. • Long-term observations of solar diffuse radiation. • Contribution of aerosols to diffuse radiation during haze and dust events. • Changes in aerosol properties during blowing dust and haze periods. [ABSTRACT FROM AUTHOR]