A critical assessment of direct radiative effects of different aerosol types on surface global radiation and its components

- A statistical method is developed to estimate aerosol effects on surface solar radiation.
- Substantial differences in aerosol radiative effects between aerosol types are revealed.
- Implication of the results is detailed discussed.

A critical assessment of direct radiative effects of different aerosol types on surface global, direct and diffuse radiation is presented. The analysis is based on measurements of aerosol optical properties and surface solar radiation (SSR) of cloud-free days at the Baseline Surface Radiation Network (BSRN) and Aerosol Robotic Network station (AERONET) of Xianghe over the North China Plain between October 2004 and May 2012. Six aerosol types are classified based on aerosol size and absorption from the AERONET retrieval products, including two coarse-mode dominated aerosol types: dust (DU: fine mode fraction (FMF)<0.4) and polluted dust (PD: FMF within 0.4-0.7) and four fine-mode dominated aerosol types (FMF>0.7) but with different single scattering albedo (SSA): highly absorbing (HA: SSA<0.85), moderately absorbing (MA: SSA within 0.85-0.90), slightly absorbing (SA: SSA within 0.90-0.95) and very weakly absorbing (WA: SSA>0.95). Dramatic differences in aerosol direct radiative effect (ADRE) on global SSR and its components between the six aerosol types have been revealed. ADRE efficiency on global SSR for solar zenight angle (SZA) between 55° and 65° ranges from −106 W m−2 for WA to −181 W m−2 for HA. The minimum ADRE efficiency on diffuse SSR is derived for HA aerosols, being 113 W m−2 that is about half of that by DU, the maximum value of six aerosol types. ADRE efficiency on global SSR by DU and PD (−141 to −150 W m−2 for SZA between 55° and 65°) is comparable to that by MA, although 100 W m−2 more direct SSR is extincted by DU and PD than by MA. DU and PD induce more diffuse SSR than MA that offsets larger reduction of direct SSR by DU and PD. Implications of the results to related researches are detailed discussed. The results are derived from aerosol and radiation data in the North China Plain, however the method can be used to any other stations with similar measurements.