Work Package Modelling (WP-M): Modeling, Parameterizations, and Synthesis of results

In Phase 1, WP-M has focused on the transfer of the INUIT laboratory and field results into parameterizations and their implementation into cloud and climate models. In an extensive review article, Hoose and Möhler (2012) have compiled the results of over 90 laboratory studies of heterogeneous ice nucleation on aerosols. Typical temperature-supersaturation regions can be identified for the “onset” of ice nucleation of mineral dust, soot, biological, organic and crystalline ammonium sulfate particles, but the various particle sizes and activated fractions reported in different studies have to be taken into account when comparing results obtained with different methodologies, for example by using the ice nucleation active site (INAS) density description.

In RP5, novel laboratory-based ice nucleation parameterizations were implemented into a mesoscale model, compared to established parameterizations for case studies of orographic clouds, and the impact on the cloud properties was quantified. In RP3, an air parcel model with detailed spectral bin cloud microphysics was used to investigate the impact of ice nucleating particle types and numbers on mixed-phase convective clouds. The model now includes drop-volume dependent homogeneous freezing as well as three heterogeneous freezing modes: immersion freezing directly related to the particle mass in the drops, contact freezing particle-size resolved, and deposition freezing as function of ice supersaturation. Included are parameterizations for various ice nucleating particle types (Diehl and Mitra, 2015).

In INUIT Phase 2, this work package will focus on the numerical assessment of heterogeneous ice nucleation in the atmosphere and its importance for cloud parameters. The specific WP-M objectives are the following:

• Assess the atmospheric relevance of the ice nucleation regimes (temperature, relative humidity and INP concentrations) probed in WP-L and WP-F
• Contribute to the setup and demonstrate the use of the new community database for published laboratory results on ice nucleation (with WP-L).
• Extend the parameterization concepts developed during the first phase of INUIT to offer a comprehensive and consistent framework for cloud, weather and climate model (collaboration with WP-L)
• Quantify the contribution of all possible ice nucleation modes to atmospheric ice formation in different cloud regimes
• Study the sensitivity of the cloud macrostructure and precipitation amount to realistic disturbances in the INP distribution
• Extend two state-of-the art models (a 3D convection-resolving model with bin microphysics and an LES model with 2-moment microphysics) by mechanistic treatments of ice nucleation
• Lead the “potential INP closure” calculations (collaboration with WP-L and WP-F)
• Contribute modeling tools to the international ice nucleation workshops in 2015 (collaboration with WP-F and WP-L)