The effect of aerosol on downward diffuse radiation during winter haze in Wuhan, China

The effect of aerosol on diffuse radiation (DR) are examined using ground-based observation and radiative transfer simulation at Wuhan during the winter haze periods of 2015 and 2016. The results show that the DR values change with the severity of the pollution, from 156.51 W/m2 under clean air conditions to 157.52 W/m(2) during severe pollution periods, while the ratio of DR to global radiation increases from 57% to 73% accordingly. Both DR and the ratio of DR to global radiation are significantly correlated with aerosol optical depth (AOD), with determination coefficient being 0.67 and 0.92, respectively. In addition, the aerosol forward scattering increased along with clean air to serious pollution, showing a logarithmic growth relationship with the effective radius of the fine-mode particles. The aerosol diffuse radiative effect (ADRE) was introduced to quantify aerosol's effect on DR, which increased from 122.83 W/m(2) under clean air condition to 152.84 W/m(2) during common pollution period and 180.99 W/m(2) during severe pollution period. The sensitivity test of ADRE to aerosol optical properties show that the increase of ADRE is dominated by increase in AOD, and also related to increase in asymmetry factor (ASY) due to hygroscopic growth of fine mode particles under pollution conditions. The above findings enhance our understanding of the mechanisms governing ADRE variation during haze periods and favor the accurate evaluation of both the diffuse radiative effect of aerosols on the climate.

Automated summary

The study found that the impact of aerosols on diffuse radiation is related to the severity of pollution, with the ratio of diffuse radiation increasing as pollution worsens. Aerosol optical properties are significantly correlated with diffuse radiation and its ratio, and the forward scattering of aerosols and aerosol diffuse radiative effect respond differently to pollution levels.