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Logo: Institute of Meteorology and Climatology /Leibniz Universität Hannover
Logo Leibniz Universität Hannover
Logo: Institute of Meteorology and Climatology /Leibniz Universität Hannover
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Current Projects

Research Projects

From the sound source to psycho-acoustic assessment (WEA-Akzeptanz)

 

Supervisor:

Günter Groß, Siegfried Raasch

Researcher:

Christoph Knigge

Duration:

2017-2019

Funded by:

BMWi

Brief description:

The aim of this project is the development of a model chain which allows the prediction of sound emission and propagation of wind turbines before construction in order to prevent disturbance to residents.

 

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Model-based city planning and application in climate change (MOSAIK)

Bild zum Projekt Model-based city planning and application in climate change (MOSAIK)

Supervisor:

Björn Maronga, Günter Groß, Siegfried Raasch, Gunther Seckmeyer

Researcher:

Tobias Gronemeier, Matthias Sühring, Farah Kanani-Sühring, Robert von Tils, Michael Schrempf

Duration:

2016-2019

Funded by:

BMBF

Brief description:

The goal of the project is the development of a new innovative urban climat model that is able to simulate the microclimate in densely-populated cities like Berlin with a spatial resolution of less than 10 m. The model will be developed as a user-friendly tool, which can be applied by both scientists and urban planners.

 

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A new LES-based system for short-range forecasting of near-surface high impact weather at airports (ALERT)

Bild zum Projekt A new LES-based system for short-range forecasting of near-surface high impact weather at airports (ALERT)

Supervisor:

Björn Maronga, Siegfried Raasch

Researcher:

Helge Knoop

Duration:

2016-2019

Funded by:

Deutscher Wetterdienst (DWD)

Brief description:

The project aims to improve the local forecast of atmospheric surface layer processes and quantities for airport areas with a focus on the precise forecast of critical events such as radiation and advection fog as well as wind gusts by using high-resolution large-eddy simulations (LES).

 

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HD(CP)2 (2nd phase): Flux heterogeneity and boundary layer circulations

Bild zum Projekt HD(CP)2 (2nd phase): Flux heterogeneity and boundary layer circulations

Supervisor:

Siegfried Raasch, Björn Maronga

Researcher:

Katrin Scharf

Duration:

2016-2019

Funded by:

BMBF

Brief description:

In nature, atmospheric state variables are modified by surface flux variations at all scales, which are induced by dynamic (vegetation growth, land use management) surface heterogeneities, and which feedback on larger scale atmospheric boundary layer (ABL) fluxes. ABL circulations driven by these heterogeneities modify the surface fluxes resulting in two-way feedbacks and impacts on even extended circulations. Sub grid-scale heterogeneity of land surfaces in climate models is usually tackled by the tile approach, which assumes a homogeneous atmosphere interacting with a heterogeneous land surface. In this approximation, the atmosphere is solely driven by grid-averaged fluxes at the surface. This project will quantify the effect of climate model sub-grid flux variability including induced boundary circulations within the scale of the climate model grid cell and their feedbacks on the fluxes on the uncertainty of regional climate predictions. The main intention is to explicitly resolve the near-surface processes both in order to gain a better physical understanding, and to quantify errors in the existing weather forecasting model ICON surface parameterizations and suggest improvements.

 

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High-resolution numerical studies on the effect of turbulence on nocturnal radiation fogs

Bild zum Projekt High-resolution numerical studies on the effect of turbulence on nocturnal radiation fogs

Supervisor:

Björn Maronga

Researcher:

Johannes Schwenkel

Duration:

2015-2017

Funded by:

DFG

Brief description:

In this project, high-resolution large-eddy simulations (LES) will be used to investigate the effect of turbulence on nocturnal radiation fogs. The LES model PALM will be used at very high resolution in the order of 1 m with both an Eulerian bulk cloud physics scheme and an embedded Lagrangian particle model that allows for explicitly resolving aerosols and fog droplets will be employed. This innovative approach allows for studying fog droplet-turbulence interactions for the first time with LES. The aim of this study is to achieve a comprehensive view on the key parameters that determine the life cycle of radiation fog as well as its three-dimensional macro- and microstructure. Moreover, the effect of a nocturnal fog layer on the morning transition and the daytime boundary layer will be studied. The effect of surface heterogeneity on nocturnal radiation fog will be investigated by means of LES with prescribed idealized regular and observed irregular surface heterogeneities.

 

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Large-eddy simulation as a tool for wind turbine site assessment in complex terrain

 

Supervisor:

Siegfried Raasch

Researcher:

Lennart Böske, Christoph Knigge

Duration:

2015-2017

Brief description:

Especially in complex terrain, atmospheric turbulence is a challenge for the planning of new wind turbines and parks. Orographic induced turbulence can significantly increase loads on the turbines, and hence drastically reduce their life span. In the current wind turbine site assessment, only Reynolds-averaged Navier-Stokes (RANS) models are used, in which the whole spectrum of turbulence is parametrized. Especially for complex terrain, RANS models often fail to represent the effects of turbulence correctly. The aim of this project is to demonstrate the operational application of the turbulence-resolving LES model PALM for wind turbine site assessment and to point out its advantages over RANS modeling. For that purpose, high-resolution LES of the turbulent wind field at an existing wind turbine site are conducted and the results validated with measurement data. For further model validation by means of wind tunnel measurement data, the flow over an idealized mountain is simulated. These idealized simulations additionally help to optimize the numerical setup for a potential industrial application of PALM in the future.

 

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Entrainment of aerosols and their activation in shallow cumulus clouds - Large-eddy simulations with an embedded Lagrangian particle model

 

Supervisor:

Siegfried Raasch

Researcher:

Fabian Hoffmann

Duration:

01/04/2014-31/03/2017

Funded by:

DFG

Brief description:

Shallow cumulus clouds are affecting the climate in many ways. One main impact is the reflection of extraterrestrial shortwave radiation (albedo), which is regulated by the amount and spectral distribution of cloud droplets and, therefore, the amount of aerosols. However, only activated aerosols can serve as condensation nuclei for cloud droplets. Primary activation of aerosols takes place at the cloud base by the adiabatic cooling of rising air parcels. For the activation above cloud base (secondary activation) two explanations exist: (i) the activation of aerosols, which are too small to be activated at cloud base, and (ii) the lateral entrainment of aerosols into the cloud and their subsequent activation in the supersaturated environment of the cloud. The general objective of the current project is to obtain an improved understanding of the processes which lead to the activation of aerosols in shallow cumulus by applying large eddy simulations (LES) and a Lagrangian particle model (LPM) to parameterize cloud physics, in which Lagrangian particles (so-called super-droplets) represent a certain number of real droplets/aerosols of the same features (e.g., droplet size, mass of aerosol). This Lagrangian perspective of cloud physics allows tracking of individual droplets/aerosols and the direct calculation of entrainment rates. This is required and will be used to quantify how the different processes of activation contribute to the amount and spectral distribution of cloud droplets during the life-cycle of an individual cloud, in a cloud ensemble (i.e., dependencies on cloud features like cloud height) or under different background aerosol conditions.

 

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Master's Theses / Diploma Theses

Staubtransport durch Staubteufel – Eine LES-Studie

 

Supervisor:

Siegfried Raasch

Researcher:

Veit Rautmann

Brief description:

Dieses Projekt zielt darauf ab, den durch Staubteufel verursachten Eintrag von Staubpartikeln in die Atmosphäre anhand von LES zu untersuchen.

 

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