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

• Published in: Geoscientific Model Development 2017-06, Vol.10 (6), p.2231-2246
• Main Authors: Dipu, Sudhakar, Quaas, Johannes, Wolke, Ralf, Stoll, Jens, Mühlbauer, Andreas, Sourdeval, Odran, Salzmann, Marc, Heinold, Bernd, Tegen, Ina
• Format: Article
• Language: English
• Subjects: Aerosol effects; Aerosol transport; Aerosol-cloud interactions; Aerosols; Atmosphere; Atmospheric circulation; Atmospheric models; Case studies; Chemistry; Cloud chemistry; Cloud computing; Cloud condensation nuclei; Cloud condensation nuclei concentrations; Cloud droplet concentration; Cloud droplet size; Cloud droplets; Cloud microphysics; Cloud optical depth; Cloud-climate relationships; Clouds; Clouds (Meteorology); Complexity; Computer simulation; Condensation; Condensation nuclei; Consortia; Droplets; Environmental aspects; Feedback; General circulation models; Intercomparison; Internet; Modelling; Observations; Ocean, Atmosphere; Optical analysis; Optical properties; Optical thickness; Precipitation; Radiation; Radiations; Rain; Regional analysis; Satellite data; Satellites; Scale models; Scavenging; Sciences of the Universe; Simulators; Small-scale models; Transportation models
• ISSN: 1991-9603; 1991-959X; 1991-962X; 1991-9603; 1991-962X; 1991-959X
• DOI: 10.5194/gmd-10-2231-2017

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 %.