Droplet freezing in clouds induced by mineral dust particles: Sensitivities of precipitation and radiation

We aim to enhance our understanding of cloud microphysical processes under conditions of varying droplet freezing efficiencies in numerical simulations of Arctic mixed-phase stratocumulus and isolated deep convective clouds. A novel framework of immersion freezing is implemented in the model, considering the collisions of droplets and subsequent particle accumulation in rain-sized drops. The sensitivity of clouds is investigated in a wide range of atmospherically-relevant dust concentrations

Systems Competence: Operationalization, Evaluation and Theoretic Classification

This thesis pursues the question of how trainings for counseling competences have to be laid out to be effective and how evaluation procedures have to be set up to capture the competence development in this field. The construct systems competence is the starting point for these thoughts. It lists the competences, skills, abilities, and knowledge aspects that are necessary for working with complex, social systems. It is based on the theoretical considerations of Synergetics; a systems theory that describes the creation of a system’s macroscopical, coherent patterns upon the self-organization of its system elements without external influences. The construct systems competence describes counselors’ competences that are needed to provide the conditions for self-organization in individuals or teams. In order to allow for appropriate operationalization, three facets are selected: Basic Knowledge of Synergetics, Idiographic System Modeling, and Generic Principles. For each, a training program and specific evaluation instruments are developed. The findings of competence development research suggest various taxonomies of competences and models. Also, conditions are described which help to enhance competences. Based upon these suggestions a training and evaluation instruments are developed. The training puts a strong emphasis on open-learning settings, complex scenarios, a high degree of experiential learning, reflection and exercises. Since the improvement of counseling competences is the subject of this thesis two of the selected facets are operationalized and evaluated in counseling interviews (Idiographic System Modeling, Generic Principles). The basic knowledge of Synergetics is evaluated via a knowledge test. In 2007, a preliminary study among the members of the professional organization “Systemische Gesellschaft” and “Deutsche Gesellschaft für Systemische Therapie und Familientherapie” revealed that competence assessment of participants in training classes is very common. But, the procedures of these assessments vary greatly in their systematics, and formal assessments with checklists are very rare. Therefore, evaluation instruments are developed consisting of a mixture of assessment modes including different perspectives and levels of external rating. Different self-assessment and observation schemes are applied. The training follows the approach of a spiral curriculum accompanied by a pre-post evaluation and an intermediate evaluation between two evaluation rounds. University students and participants of a systemic training course make up the sample of this study. The results of the study show the participants improved their competences in all three facets. The most significant improvement is observed for the gain of knowledge whereas university students receive higher scores compared to the other participants of the training. For the two counseling procedures with which the Idiographic System Modeling and the Generic Principles are operationalized, the degree of the observed improvement strongly depends on the applied evaluation perspective. Whereas external raters state an improvement, the respective counselors do not report any. One further outcome of this thesis is the reorganization of the construct systems competence according to the findings of competence research. The findings of this thesis can be utilized to improve feedback methods in counseling trainings and to reach more objective means of competence assessment in adult education

Intercomparison of Large-Eddy Simulations of Arctic Mixed-Phase Clouds: Importance of Ice Size Distribution Assumptions

Large-eddy simulations of mixed-phase Arctic clouds by 11 different models are analyzed with the goal of improving understanding and model representation of processes controlling the evolution of these clouds. In a case based on observations from the Indirect and Semi-Direct Aerosol Campaign (ISDAC), it is found that ice number concentration, Ni, exerts significant influence on the cloud structure. Increasing Ni leads to a substantial reduction in liquid water path (LWP), in agreement with earlier studies. In contrast to previous intercomparison studies, all models here use the same ice particle properties (i.e., mass-size, mass-fall speed, and mass-capacitance relationships) and a common radiation parameterization. The constrained setup exposes the importance of ice particle size distributions (PSDs) in influencing cloud evolution. A clear separation in LWP and IWP predicted by models with bin and bulk microphysical treatments is documented and attributed primarily to the assumed shape of ice PSD used in bulk schemes. Compared to the bin schemes that explicitly predict the PSD, schemes assuming exponential ice PSD underestimate ice growth by vapor deposition and overestimate mass-weighted fall speed leading to an underprediction of IWP by a factor of two in the considered case. Sensitivity tests indicate LWP and IWP are much closer to the bin model simulations when a modified shape factor which is similar to that predicted by bin model simulation is used in bulk scheme. These results demonstrate the importance of representation of ice PSD in determining the partitioning of liquid and ice and the longevity of mixed-phase clouds

An architecture blueprint for knowlege-based e-Science

The scientific innovation process embraces the steps from problem definition through the development and evaluation of innovative solutions to their successful exploitation. The challenges imposed by this process can be answered by the creation of a powerful and flexible next-generation e-Science infrastructure, which exploits leading edge information and knowledge technologies and enables a comprehensive and intelligent means of supporting this process. This paper describes our vision of a Knowledge-based eScience infrastructure, which is based on the results of an in-depth study of the researchers requirements. Furthermore, it introduces the Fraunhofer e-Science Cockpit as a first implementation of our vision

A Modeling Study on the Sensitivities of Atmospheric Charge Separation According to the Relative Diffusional Growth Rate Theory to Nonspherical Hydrometeors and Cloud Microphysics

Collisional charge transfer between graupel and ice crystals in the presence of cloud droplets is considered the dominant mechanism for charge separation in thunderclouds. According to the relative diffusional growth rate (RDGR) theory, the hydrometeor with the faster diffusional radius growth is charged positively in such collisions. We explore sensitivities of the RDGR theory to nonspherical hydrometeors and six parameters (pressure, temperature, liquid water content, sizes of ice crystals, graupel, and cloud droplets). Idealized simulations of a thundercloud with two‐moment cloud microphysics provide a realistic sampling of the parameter space. Nonsphericity and anisotropic diffusional growth strongly control the extent of positive graupel charging. We suggest a tuning parameter to account for anisotropic effects not represented in bulk microphysics schemes. In a susceptibility analysis that uses automated differentiation, we identify ice crystal size as most important RDGR parameter, followed by graupel size. Simulated average ice crystal size varies with temperature due to ice multiplication and heterogeneous freezing of droplets. Cloud microphysics and ice crystal size thus indirectly determine the structure of charge reversal lines in the traditional temperature‐water‐content representation. Accounting for the variability of ice crystal size and potentially habit with temperature may help to explain laboratory results and seems crucial for RDGR parameterizations in numerical models. We find that the contribution of local water vapor from evaporating rime droplets to diffusional graupel growth is only important for high effective water content. In this regime, droplet size and pressure are the dominant RDGR parameters. Otherwise, the effect of local graupel growth is masked by small ice crystal sizes that result from ice multiplication.ISSN:0148-0227ISSN:2169-897