Browsing by Subject "Luftfahrt"

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A backscatter lidar forward operator for aerosol-representing atmospheric chemistry models
(2020) Geisinger, Armin; Wulfmeyer, Volker
State-of-the-art atmospheric chemistry models are capable of simulating the transport and evolution of aerosols and trace gases but there is a lack of reliable methods for model validation and data assimilation. Networks of automated ceilometer lidars (ACLs) could be used to fill this gap. These networks are already used for the detection of clouds and aerosols, providing a 3D dataset of atmospheric backscatter profiles. But as the aerosol number concentration cannot be obtained from the ACL data alone; one needs a backscatter-lidar forward model to simulate lidar profiles from the model variables. Such an operator allows then for a qualitative and quantitative model validation based on ACL data. In this work, a newly developed backscatter-lidar forward operator and the related sensitivity studies are presented and results of the forward operator applied on model output data are compared to measured ACL profiles in the frame of a case study. As case study, the eruption of the Icelandic volcano Eyjafjallajökull in 2010 was chosen and extensively analyzed. The Consortium for Small-scale Modeling - Aerosols and Reactive Trace gases (COSMO-ART) model of DWD (Deutscher Wetterdienst) was operated during this event for ash-transport simulations over Europe. For the forward model, the attenuated backscatter coefficient is used as lidar-independent variable, which only relies on the laser wavelength. To calculate the attenuated backscatter coefficient, the size-dependent aerosol number concentration and the scattering properties of each aerosol type and size have to be simulated. While the aerosol number concentration is a model output variable, the scattering properties were determined by extensive scattering calculations. As these scattering calculations require assumptions about the aerosol refractive indices and shapes, sensitivity studies were performed to estimate the uncertainties related to the particle properties as represented by the model system. An analysis of the particle shape effect for the extinction and backscatter coefficients resulted in huge differences of the scattering properties between spherical, ellipsoidal and cylindrical particle shapes. Due to a particle shape mixture in typical volcanic ash plumes, the application of non-spherical scattering calculation methods for estimating the effective optical properties requires more information related to the particle shape distribution (specifically: a particle size and shape distribution). As such information was not available for the present case study, it was necessary to assume spherical shaped volcanic ash particles but estimate the uncertainty related to this assumption within the frame of additional sensitivity studies. Finally, the forward modeled lidar profiles were compared to ACL measurements from stations of the German ACL network. The comparison required an extraction of common time and height intervals of the ACL and forward modeled COMSO-ART data as well as reshaping the datasets to the same vertical and temporal resolution. Significant differences between ACL profiles and the output of the forward operator applied to the COSMO-ART data were found. Some ash layer structures were at similar coordinates which is remarkable due to the uncertainties related to the model dynamics and the limited amount of measurement data that could be used for model validation. In detail, however, the major fraction of the compared time and height interval differed both in the relative signal intensity and the layer structures of the volcanic ash plume. Based on such quantitative comparison, a future data assimilation system could correct the model prediction of the forward modeled attenuated backscatter coefficient, the time of arrival, as well as the vertical structure of the volcanic ash plume. In summary, the continuous and distributed data stream provided by ACL stations was found to deliver valuable verification information for dispersion simulations of aerosol events. But major issues have been determined which limit current realizations of backscatter-lidar forward operators for aerosol transport simulations: First, it is suggested that the ACL systems improve their dynamic range and perform automatic calibration to increase the precision of ACL data and for calculating the measured attenuated backscatter coefficient with a minimum leftover of uncertainties. This will allow for the calculation of the attenuated backscatter coefficient in the presence of clouds as well as of faint aerosol signals. Second, the aerosols scattering properties have to be analyzed even more extensively which includes both the variety of aerosol sizes or types as well as the size distribution information. From the findings within this study, the particle size distribution was indentified to be a critical component when using monodisperse size classes.
Ambidextrie in Netzwerken komplexer Produkte : Exploration und Exploitation in der Luftfahrtindustrie
(2016) Guffarth, Daniel; Pyka, Andreas
Since over 100 years, no comparable product exists that is so strongly related with engineering skills, pioneering spirit and the complex combination of materials, technique and knowledge, while being a prototypical example for high development and production cost at the same time. During the last century, industry changed dramatically through evolutionary and revolutionary technical and structural changes with government intervention playing a key role for industrial evolution. Today’s aircraft industry is in a growth phase which is determined by ramping up production scales which leads, in combination with the potentially new competitors from Asia and uprising regional aircraft manufacturers, to a situation in which the duopolists Airbus and Boeing are forced to shape their supply chains more efficient and effective. At the same time continuous technological novelties in subsystems and the high R&D-intensity are further recent challenges. With this dissertation a new industry evolution framework is developed which is coping with the complex products industries requirements by considering demand, state intervention and technological mechanisms. In complex product systems different subsystems of the artefact aircraft are in different stages of the technological life cycle at the same time. This is the reason why the classical implications between technology, product, and industry life cycle stages do not hold for complex products industries. I.e. solely focusing on the manufacturer level of an industry is not sufficient. Therefore in this dissertation, industry is defined as network. The design of this network as exploration or exploitation network focusing on product or process and/or both depends on time and manner. As permanently changing requirements are characteristic for complex products, organizations have to be able to be ambidextrous, i.e. to balance exploration and exploitation which is a decisive success factor in organizational long term survival. This requirement is analyzed on three levels within the R&D network of the European aircraft industry: knowledge development, structural and network topology, as well as on regional development. Key findings are the extension of ambidexterity in the network as well as in the supply chain over time. Therefore a change from cyclical to permanent ambidexterity is directed towards the suppliers. Additionally exploration is crowded out from the core of the network as routines and fossilized structure are established over time by repeatedly cooperating with other core actors. Therefore core actors use network peripheries as a vehicle to realize explorative projects and being permanently ambidextrous. As a consequence success factors for the sustainability of the European aircraft industry are the orchestration of network stability and network heterogeneity as well as the maintenance of the SME structure and interindustry linkages for usage of explorative learning.
The European aerospace R&D collaboration network
(2013) Barber, Michael J.; Guffarth, Daniel
We describe the development of the European aerospace R&D collaboration network from 1987 to 2013 with the help of the publicly available raw data of the European Framework Programmes and the German Förderkatalog. In line with the sectoral innovation system approach, we describe the evolution of the aerospace R&D network on three levels. First, based on their thematic categories, all projects are inspected and the development of technology used over time is described. Second, the composition of the aerospace R&D network concerning organization type, project composition and the special role of SMEs is analyzed. Third, the geographical distribution is shown on the technological side as well as on the actor level. A more complete view of the European funding structure is achieved by replicating the procedure on the European level to the national level, in our case Germany.