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Logo: Institut für Meteorologie und Klimatologie/Leibniz Universität Hannover
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Logo: Institut für Meteorologie und Klimatologie/Leibniz Universität Hannover
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Projekte von Dr. Micha Gryschka

Forschungsprojekte

Modellierung und Parametrisierung von durch Rinnen generierter Turbulenz in der atmosphärischen Grenzschicht über Eis

Bild zum Projekt Modellierung und Parametrisierung von durch Rinnen generierter Turbulenz in der atmosphärischen Grenzschicht über Eis

Leitung:

Micha Gryschka

Bearbeitung:

Xu Zhou

Laufzeit:

2017-2020

Förderung durch:

DFG

Kurzbeschreibung:

In diesem Projekt soll ein tieferes Verständnis über die turbulenten Austauschprozesse zwischen Ozean und Atmosphäre über polaren Eisrinnen erworben werden, mit dem Ziel Parametrisierungen dieser Prozesse für Wetter- und Klimamodelle zu verbessern.

 

Details

 

Representation of the convective atmospheric boundary layer during cold-air outbreaks in regional models: a joined study based on observations, Large Eddy Simulation and mesoscale modelling

 

Leitung:

Siegfried Raasch

Bearbeitung:

Christof Lüpkes, Siegfried Raasch, Micha Gryschka, Jens Fricke

Laufzeit:

2010-2015

Förderung durch:

DFG

Kurzbeschreibung:

The interaction between atmospheric processes in polar and mid-latitude regions is strongly affected by cold-air outbreaks (CAOs). During such events cold air originating from (sea)ice covered regions is transported over large distances towards lower latitudes, while over open water a shallow but strongly heated convective boundary layer develops. Although the present generation of weather and regional climate models captures CAOs qualitatively well, there are deficiencies caused by uncertainties in the representation of the multi scale physical CAO processes in models. Open questions concern e.g., the generation of rolls under conditions of strong thermal forcing over the open and partially ice covered ocean and under non- stationary synoptic conditions. Other questions are related to the parameterization of the strong turbulent fluxes, especially in coarse grid resolution. Hence this project aims to study the physical processes in polar CAOs with roll vortices using large eddy simulation (LES) and mesoscale modelling. Furthermore, parameterizations of turbulence in CAOs will be improved with a focus on the most modern low order closures and their applicability to regional scale models. To this end current and new closures are used in a mesoscale model with different resolutions and its results are compared with observations and with the results of LES.

 

Details

 

Coupled atmosphere-ice-ocean turbulence resolving model

 

Leitung:

Siegfried Raasch, Igor Esau

Bearbeitung:

Marcus Oliver Letzel, Björn Maronga, Micha Gryschka

Laufzeit:

2007-2014

Kurzbeschreibung:

The project objective is to develop a coupled lower atmosphere-ice-upper ocean turbulence resolving model able to simulate interactions between atmospheric and ocean turbulence in presence of sea ice freezing, melting and transporting mechanisms.

 

Details

 

Masterarbeiten / Diplomarbeiten

Large-eddy simulation of cold air outbreaks with a stationary domain

 

Bearbeitung:

Micha Gryschka

Laufzeit:

2002-2003

Kurzbeschreibung:

With recent simulations (Schröter) the PALM group could show that all LES based computations of roll vortices during cold air outbreaks are due to modell insufficiencies, i.e. unphysical conditions. One possible reason could be that a slanted inversion is needed for the generation of roll vortices and thereby a shear flow at the top of the boundary layer. To examine this, it is necessary to simulate the ABL with a stationary model domain. Therefore noncylic lateral boundaries must be implemented into the PALM code, which is part of the work of this thesis.

 

Details