Dust IN concentrations and the impact on clouds in COSMO

One of the main sources of uncertainty in climate simulations is the role aerosols have in influencing the physical properties of clouds. Mineral dust particles, mostly emitted from deserts, have been identified as the main contributor to atmospheric ice nucleation. A significant Saharan dust outbreak in May 2008 transported large amounts of dust particles over Europe. Background dust concentrations during this month were about an order of magnitude higher than normal. From modeled dust concentrations, parameterisations based on laboratory experiments for deposition and immersion freezing were used to estimate ice nuclei number concentrations. The ice nuclei number concentrations during this dust outbreak were also approximately an order of magnitude larger than normal. As direct observations for the simulated time period in Europe are not available, the results are compared in a statistical sense to in-situ observations from other regions, taken under comparable environmental conditions. The resulting ice nuclei fields are prepared as input for simulations using the Consortium for Small-scale Modleing (COSMO) limited area model, with the goal of assessing the influence a realistic representation of ice nuclei has on cloud precipitation and radiative properties.