Radiative effects of UTLS aerosols in climate simulations

The UTLS (upper troposphere lower stratosphere) is known for its strong susceptibility of changes of the radiative impact of their constituents, with effects relevant also for near surface temperatures. To assess the effects of particulate radiative effects, we have developed a new calculation scheme for the optical properties of internally and externally mixed aerosol compounds both in the shortwave (visible and near-infrared) and the longwave spectrum, differentiating between scattering and absorbing contributions. The scheme is easily extendable to consider specific compounds, e.g., including volcanic ash or differentiating between organics from anthropogenic sources versus biogenic SOA.
This scheme has been implemented into the chemistry climate model EMAC to investigate the effects of aerosol radiative impacts in the UTLS on the troposphere. This study shows corresponding results, including an assessment of how the refractive indices of the individual compounds have an overall impact on the global radiative effects.