The effect of aerosols on long wave radiation and global warming

The effect of aerosols on long wave (LW) radiation was studied based on narrowband LW calculations in a reference mid-latitude summer atmosphere with and without aerosols. Aerosols were added to the narrowband LW scheme based on their typical schematic observed spectral and vertical behaviour over European land areas. This was found to agree also with the spectral aerosol data from the Lan Zhou University Semi-Arid Climate Observatory and Laboratory measurement stations in the north-western China. A volcanic stratospheric aerosol load was found to induce local LW warming and a stronger column "greenhouse effect" than a doubled CO2 concentration. A heavy near-surface aerosol load was found to increase the downwelling LW radiation to the surface and to reduce the outgoing LW radiation, acting very much like a thin low cloud in increasing the LW greenhouse effect of the atmosphere. The short wave reflection of white aerosol has, however, stronger impact in general, but the aerosol LW greenhouse effect is non-negligible under heavy aerosol loads.