A case study on microphysical and radiative properties of power-plant-originated clouds

Cloud microphysical characteristics and solar cloud albedo of a stratiform cloud field downwind a coal-fired power plant and of naturally formed stratiform continental clouds are compared. In situ measurements of aerosol, drop microphysical, and solar radiative parameters of both cloud types are complemented by one- and three-dimensional radiative transfer calculations. The aerosol particle concentrations in and around the power-plant-originated clouds were significantly enhanced and the cloud drop concentrations were nearly doubled in comparison with the naturally formed clouds, whereas the effective cloud drop radius remained roughly unchanged. The radiation measurements as well as the modeling revealed a higher solar albedo of the power-plant-originated cloud compared to the surrounding natural clouds. Even when high amounts of absorbing material were assumed in the drops of the power plant cloud, the calculations showed a higher albedo of this cloud. The possibility that the power plantʹs water vapor emissions significantly alter the cloud microphysics downwind the power plant is discussed.