Articles | Volume 10, issue 6
Geosci. Model Dev., 10, 2231–2246, 2017
Geosci. Model Dev., 10, 2231–2246, 2017

Model evaluation paper 20 Jun 2017

Model evaluation paper | 20 Jun 2017

Implementation of aerosol–cloud interactions in the regional atmosphere–aerosol model COSMO-MUSCAT(5.0) and evaluation using satellite data

Sudhakar Dipu1, Johannes Quaas1, Ralf Wolke2, Jens Stoll2, Andreas Mühlbauer3, Odran Sourdeval1, Marc Salzmann1, Bernd Heinold2, and Ina Tegen2 Sudhakar Dipu et al.
  • 1Institute for Meteorology, Universität Leipzig, Leipzig, Germany
  • 2Leibniz Institute for Tropospheric Research, Leipzig, Germany
  • 3FM Global Research, Norwood, MA, USA

Abstract. The regional atmospheric model Consortium for Small-scale Modeling (COSMO) coupled to the Multi-Scale Chemistry Aerosol Transport model (MUSCAT) is extended in this work to represent aerosol–cloud interactions. Previously, only one-way interactions (scavenging of aerosol and in-cloud chemistry) and aerosol–radiation interactions were included in this model. The new version allows for a microphysical aerosol effect on clouds. For this, we use the optional two-moment cloud microphysical scheme in COSMO and the online-computed aerosol information for cloud condensation nuclei concentrations (Cccn), replacing the constant Cccn profile. In the radiation scheme, we have implemented a droplet-size-dependent cloud optical depth, allowing now for aerosol–cloud–radiation interactions. To evaluate the models with satellite data, the Cloud Feedback Model Intercomparison Project Observation Simulator Package (COSP) has been implemented. A case study has been carried out to understand the effects of the modifications, where the modified modeling system is applied over the European domain with a horizontal resolution of 0.25°  ×  0.25°. To reduce the complexity in aerosol–cloud interactions, only warm-phase clouds are considered. We found that the online-coupled aerosol introduces significant changes for some cloud microphysical properties. The cloud effective radius shows an increase of 9.5 %, and the cloud droplet number concentration is reduced by 21.5 %.